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Patch series "move all VMA allocation, freeing and duplication logic to
mm", v3.
Currently VMA allocation, freeing and duplication exist in kernel/fork.c,
which is a violation of separation of concerns, and leaves these functions
exposed to the rest of the kernel when they are in fact internal
implementation details.
Resolve this by moving this logic to mm, and making it internal to vma.c,
vma.h.
This also allows us, in future, to provide userland testing around this
functionality.
We additionally abstract dup_mmap() to mm, being careful to ensure
kernel/fork.c acceses this via the mm internal header so it is not exposed
elsewhere in the kernel.
As part of this change, also abstract initial stack allocation performed
in __bprm_mm_init() out of fs code into mm via the
create_init_stack_vma(), as this code uses vm_area_alloc() and
vm_area_free().
In order to do so sensibly, we introduce a new mm/vma_exec.c file, which
contains the code that is shared by mm and exec. This file is added to
both memory mapping and exec sections in MAINTAINERS so both sets of
maintainers can maintain oversight.
As part of this change, we also move relocate_vma_down() to mm/vma_exec.c
so all shared mm/exec functionality is kept in one place.
We add code shared between nommu and mmu-enabled configurations in order
to share VMA allocation, freeing and duplication code correctly while also
keeping these functions available in userland VMA testing.
This is achieved by adding a mm/vma_init.c file which is also compiled by
the userland tests.
This patch (of 4):
There is functionality that overlaps the exec and memory mapping
subsystems. While it properly belongs in mm, it is important that exec
maintainers maintain oversight of this functionality correctly.
We can establish both goals by adding a new mm/vma_exec.c file which
contains these 'glue' functions, and have fs/exec.c import them.
As a part of this change, to ensure that proper oversight is achieved, add
the file to both the MEMORY MAPPING and EXEC & BINFMT API, ELF sections.
scripts/get_maintainer.pl can correctly handle files in multiple entries
and this neatly handles the cross-over.
[akpm@linux-foundation.org: fix comment typo]
Link: https://lkml.kernel.org/r/80f0d0c6-0b68-47f9-ab78-0ab7f74677fc@lucifer.local
Link: https://lkml.kernel.org/r/cover.1745853549.git.lorenzo.stoakes@oracle.com
Link: https://lkml.kernel.org/r/91f2cee8f17d65214a9d83abb7011aa15f1ea690.1745853549.git.lorenzo.stoakes@oracle.com
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Reviewed-by: Suren Baghdasaryan <surenb@google.com>
Reviewed-by: Pedro Falcato <pfalcato@suse.de>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Kees Cook <kees@kernel.org>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Jann Horn <jannh@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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The variables kmemleak_enabled and kmemleak_free_enabled are read in the
kmemleak alloc and free path respectively, but are only written to if/when
kmemleak is disabled.
Link: https://lkml.kernel.org/r/4016090e857e8c4c2ade4b20df312f7f38325c15.1746046744.git.luizcap@redhat.com
Signed-off-by: Luiz Capitulino <luizcap@redhat.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Newly created objects have object->count == 0, so the comment is
incorrect. Just drop it.
Link: https://lkml.kernel.org/r/3dfd09bc0e77bb626619184a808774ff07de275c.1746046744.git.luizcap@redhat.com
Signed-off-by: Luiz Capitulino <luizcap@redhat.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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These are a trivial mm/kmemleak.c cleanups. I found these while reading
through the code.
This patch (of 3):
The kmemleak_warning variable is not used since commit c5665868183f ("mm:
kmemleak: use the memory pool for early allocations"), drop it.
Link: https://lkml.kernel.org/r/cover.1746046744.git.luizcap@redhat.com
Link: https://lkml.kernel.org/r/97e23faa7b67099027a1094c9438da5f72e037af.1746046744.git.luizcap@redhat.com
Signed-off-by: Luiz Capitulino <luizcap@redhat.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Add the missing migrate_folio operation to jfs_metapage_aops to fix
warnings during memory compaction. These warnings were introduced by
commit 7ee3647243e5 ("migrate: Remove call to ->writepage") which added
explicit warnings when filesystems don't implement migrate_folio.
System reports following warnings:
jfs_metapage_aops does not implement migrate_folio
WARNING: CPU: 0 PID: 6870 at mm/migrate.c:955 fallback_migrate_folio mm/migrate.c:953 [inline]
WARNING: CPU: 0 PID: 6870 at mm/migrate.c:955 move_to_new_folio+0x70e/0x840 mm/migrate.c:1007
Implement metapage_migrate_folio() which handles both single and multiple
metapages per page configurations.
[shivankg@amd.com: change comment style]
Link: https://lkml.kernel.org/r/1967593d-8084-4a4a-b384-35d5adc54eb4@amd.com
[akpm@linux-foundation.org: fix build]
[shivankg@amd.com: remove redundant NULL check in __metapage_migrate_folio()]
Link: https://lkml.kernel.org/r/a67db238-0ca6-4725-abb2-dc092de87e1b@amd.com
Link: https://lkml.kernel.org/r/20250430100150.279751-3-shivankg@amd.com
Fixes: 35474d52c605 ("jfs: Convert metapage_writepage to metapage_write_folio")
Signed-off-by: Shivank Garg <shivankg@amd.com>
Reported-by: syzbot+8bb6fd945af4e0ad9299@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/67faff52.050a0220.379d84.001b.GAE@google.com
Tested-by: syzbot+8bb6fd945af4e0ad9299@syzkaller.appspotmail.com
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Dave Kleikamp <shaggy@kernel.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Donet Tom <donettom@linux.ibm.com>
Cc: Jane Chu <jane.chu@oracle.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Zi Yan <ziy@nvidia.com>
Cc: Dan Carpenter <dan.carpenter@linaro.org>
Cc: kernel test robot <lkp@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Patch series " JFS: Implement migrate_folio for jfs_metapage_aops" v5.
This patchset addresses a warning that occurs during memory compaction due
to JFS's missing migrate_folio operation. The warning was introduced by
commit 7ee3647243e5 ("migrate: Remove call to ->writepage") which added
explicit warnings when filesystem don't implement migrate_folio.
The syzbot reported following [1]:
jfs_metapage_aops does not implement migrate_folio
WARNING: CPU: 1 PID: 5861 at mm/migrate.c:955 fallback_migrate_folio mm/migrate.c:953 [inline]
WARNING: CPU: 1 PID: 5861 at mm/migrate.c:955 move_to_new_folio+0x70e/0x840 mm/migrate.c:1007
Modules linked in:
CPU: 1 UID: 0 PID: 5861 Comm: syz-executor280 Not tainted 6.15.0-rc1-next-20250411-syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
RIP: 0010:fallback_migrate_folio mm/migrate.c:953 [inline]
RIP: 0010:move_to_new_folio+0x70e/0x840 mm/migrate.c:1007
To fix this issue, this series implement metapage_migrate_folio() for JFS
which handles both single and multiple metapages per page configurations.
While most filesystems leverage existing migration implementations like
filemap_migrate_folio(), buffer_migrate_folio_norefs() or
buffer_migrate_folio() (which internally used folio_expected_refs()),
JFS's metapage architecture requires special handling of its private data
during migration. To support this, this series introduce the
folio_expected_ref_count(), which calculates external references to a
folio from page/swap cache, private data, and page table mappings.
This standardized implementation replaces the previous ad-hoc
folio_expected_refs() function and enables JFS to accurately determine
whether a folio has unexpected references before attempting migration.
Implement folio_expected_ref_count() to calculate expected folio reference
counts from:
- Page/swap cache (1 per page)
- Private data (1)
- Page table mappings (1 per map)
While originally needed for page migration operations, this improved
implementation standardizes reference counting by consolidating all
refcount contributors into a single, reusable function that can benefit
any subsystem needing to detect unexpected references to folios.
The folio_expected_ref_count() returns the sum of these external
references without including any reference the caller itself might hold.
Callers comparing against the actual folio_ref_count() must account for
their own references separately.
Link: https://syzkaller.appspot.com/bug?extid=8bb6fd945af4e0ad9299 [1]
Link: https://lkml.kernel.org/r/20250430100150.279751-1-shivankg@amd.com
Link: https://lkml.kernel.org/r/20250430100150.279751-2-shivankg@amd.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Shivank Garg <shivankg@amd.com>
Suggested-by: Matthew Wilcox <willy@infradead.org>
Co-developed-by: David Hildenbrand <david@redhat.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Dave Kleikamp <shaggy@kernel.org>
Cc: Donet Tom <donettom@linux.ibm.com>
Cc: Jane Chu <jane.chu@oracle.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Add missing header inclusions.
Link: https://lkml.kernel.org/r/20250428072754.3265274-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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cpuset memory pinning
Unlike sched_skip_vma_numa tracepoint which tracks skipped VMAs, this
tracks the task subjected to cpuset.mems pinning and prints out its
allowed memory node mask.
Link: https://lkml.kernel.org/r/20250424024523.2298272-3-libo.chen@oracle.com
Signed-off-by: Libo Chen <libo.chen@oracle.com>
Cc: "Chen, Tim C" <tim.c.chen@intel.com>
Cc: Chen Yu <yu.c.chen@intel.com>
Cc: Chris Hyser <chris.hyser@oracle.com>
Cc: Daniel Jordan <daniel.m.jordan@oracle.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: K Prateek Nayak <kprateek.nayak@amd.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Madadi Vineeth Reddy <vineethr@linux.ibm.com>
Cc: Mel Gorman <mgorman <mgorman@suse.de>
Cc: Michal Koutný <mkoutny@suse.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Raghavendra K T <raghavendra.kt@amd.com>
Cc: Srikanth Aithal <sraithal@amd.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Venkat Rao Bagalkote <venkat88@linux.ibm.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Patch series "sched/numa: Skip VMA scanning on memory pinned to one NUMA
node via cpuset.mems", v5.
This patch (of 2):
When the memory of the current task is pinned to one NUMA node by cgroup,
there is no point in continuing the rest of VMA scanning and hinting page
faults as they will just be overhead. With this change, there will be no
more unnecessary PTE updates or page faults in this scenario.
We have seen up to a 6x improvement on a typical java workload running on
VMs with memory and CPU pinned to one NUMA node via cpuset in a two-socket
AARCH64 system. With the same pinning, on a 18-cores-per-socket Intel
platform, we have seen 20% improvment in a microbench that creates a
30-vCPU selftest KVM guest with 4GB memory, where each vCPU reads 4KB
pages in a fixed number of loops.
Link: https://lkml.kernel.org/r/20250424024523.2298272-1-libo.chen@oracle.com
Link: https://lkml.kernel.org/r/20250424024523.2298272-2-libo.chen@oracle.com
Signed-off-by: Libo Chen <libo.chen@oracle.com>
Tested-by: Chen Yu <yu.c.chen@intel.com>
Tested-by: Srikanth Aithal <sraithal@amd.com>
Tested-by: Venkat Rao Bagalkote <venkat88@linux.ibm.com>
Cc: "Chen, Tim C" <tim.c.chen@intel.com>
Cc: Chris Hyser <chris.hyser@oracle.com>
Cc: Daniel Jordan <daniel.m.jordan@oracle.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: K Prateek Nayak <kprateek.nayak@amd.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Madadi Vineeth Reddy <vineethr@linux.ibm.com>
Cc: Mel Gorman <mgorman <mgorman@suse.de>
Cc: Michal Koutný <mkoutny@suse.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Raghavendra K T <raghavendra.kt@amd.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Add an unit test to verify the recent mmap_changing ABI breakage.
Note that I used some tricks here and there to make the test simple, e.g.
I abused UFFDIO_MOVE on top of shmem with the fact that I know what I want
to test will be even earlier than the vma type check. Rich comments were
added to explain trivial details.
Before that fix, -EAGAIN would have been written to the copy field most of
the time but not always; the test should be able to reliably trigger the
outlier case. After the fix, it's written always, the test verifies that
making sure corresponding field (e.g. copy.copy for UFFDIO_COPY) is
updated.
[akpm@linux-foundation.org: coding-style cleanups]
Link: https://lkml.kernel.org/r/20250424215729.194656-3-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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To prevent the function from being used when CONFIG_MM_ID is disabled, we
intend to inline it into its few callers, which also would help maintain
the expected code placement.
Link: https://lkml.kernel.org/r/20250424155606.57488-1-lance.yang@linux.dev
Signed-off-by: Lance Yang <lance.yang@linux.dev>
Suggested-by: David Hildenbrand <david@redhat.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Mingzhe Yang <mingzhe.yang@ly.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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It's safer to use kmalloc_array() and size_add() because it can prevent
possible overflow problem.
Link: https://lkml.kernel.org/r/20250421062423.740605-1-suhui@nfschina.com
Signed-off-by: Su Hui <suhui@nfschina.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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container_of(node->array, ..., i_pages) just to access i_pages again is an
incredibly roundabout way of accessing node->array itself. Simplify it.
Link: https://lkml.kernel.org/r/20250421-workingset-simplify-v1-1-de5c40051e0e@suse.de
Signed-off-by: Pedro Falcato <pfalcato@suse.de>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Currently, memmap_init initializes pfn_hole with 0 instead of
ARCH_PFN_OFFSET. Then init_unavailable_range will start iterating each
page from the page at address zero to the first available page, but it
won't do anything for pages below ARCH_PFN_OFFSET because pfn_valid
won't pass.
If ARCH_PFN_OFFSET is very large (e.g., something like 2^64-2GiB if the
kernel is used as a library and loaded at a very high address), the
pointless iteration for pages below ARCH_PFN_OFFSET will take a very long
time, and the kernel will look stuck at boot time.
Use for_each_valid_pfn() to skip the pointless iterations.
Link: https://lkml.kernel.org/r/20250423133821.789413-8-dwmw2@infradead.org
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reported-by: Ruihan Li <lrh2000@pku.edu.cn>
Suggested-by: Mike Rapoport <rppt@kernel.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Tested-by: Ruihan Li <lrh2000@pku.edu.cn>
Tested-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Marc Rutland <mark.rutland@arm.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Link: https://lkml.kernel.org/r/20250423133821.789413-7-dwmw2@infradead.org
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Marc Rutland <mark.rutland@arm.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Ruihan Li <lrh2000@pku.edu.cn>
Cc: Will Deacon <will@kernel.org>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Instead of calling pfn_valid() separately for every single PFN in the
range, use for_each_valid_pfn() and only look at the ones which are.
Link: https://lkml.kernel.org/r/20250423133821.789413-6-dwmw2@infradead.org
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Marc Rutland <mark.rutland@arm.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Ruihan Li <lrh2000@pku.edu.cn>
Cc: Will Deacon <will@kernel.org>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Link: https://lkml.kernel.org/r/20250423133821.789413-5-dwmw2@infradead.org
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Marc Rutland <mark.rutland@arm.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Ruihan Li <lrh2000@pku.edu.cn>
Cc: Will Deacon <will@kernel.org>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Implement for_each_valid_pfn() based on two helper functions.
The first_valid_pfn() function largely mirrors pfn_valid(), calling into a
pfn_section_first_valid() helper which is trivial for the !VMEMMAP case,
and in the VMEMMAP case will skip to the next subsection as needed.
Since next_valid_pfn() knows that its argument *is* a valid PFN, it
doesn't need to do any checking at all while iterating over the low bits
within a (sub)section mask; the whole (sub)section is either present or
not.
Note that the VMEMMAP version of pfn_section_first_valid() may return a
value *higher* than end_pfn when skipping to the next subsection, and
first_valid_pfn() happily returns that higher value. This is fine.
[dwmw2@infradead.org: fix next_valid_pfn() for sparsemem]
Link: https://lkml.kernel.org/r/c15100fcf6781a60b852c4dbb43bdc98a678fcf0.camel@infradead.org
Link: https://lkml.kernel.org/r/20250423133821.789413-4-dwmw2@infradead.org
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Marc Rutland <mark.rutland@arm.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Ruihan Li <lrh2000@pku.edu.cn>
Cc: Will Deacon <will@kernel.org>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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In the FLATMEM case, the default pfn_valid() just checks that the PFN is
within the range [ ARCH_PFN_OFFSET .. ARCH_PFN_OFFSET + max_mapnr ).
The for_each_valid_pfn() function can therefore be a simple for() loop
using those as min/max respectively.
Link: https://lkml.kernel.org/r/20250423133821.789413-3-dwmw2@infradead.org
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Marc Rutland <mark.rutland@arm.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Ruihan Li <lrh2000@pku.edu.cn>
Cc: Will Deacon <will@kernel.org>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Patch series "mm: Introduce for_each_valid_pfn()", v4.
There are cases where a naïve loop over a PFN range, calling pfn_valid()
on each one, is horribly inefficient. Ruihan Li reported the case where
memmap_init() iterates all the way from zero to a potentially large value
of ARCH_PFN_OFFSET, and we at Amazon found the reserve_bootmem_region()
one as it affects hypervisor live update. Others are more cosmetic.
By introducing a for_each_valid_pfn() helper it can optimise away a lot of
pointless calls to pfn_valid(), skipping immediately to the next valid PFN
and also skipping *all* checks within a valid (sub)region according to the
granularity of the memory model in use.
This patch (of 7)
Especially since commit 9092d4f7a1f8 ("memblock: update initialization of
reserved pages"), the reserve_bootmem_region() function can spend a
significant amount of time iterating over every 4KiB PFN in a range,
calling pfn_valid() on each one, and ultimately doing absolutely nothing.
On a platform used for virtualization, with large NOMAP regions that
eventually get used for guest RAM, this leads to a significant increase in
steal time experienced during kexec for a live update.
Introduce for_each_valid_pfn() and use it from reserve_bootmem_region().
This implementation is precisely the same naïve loop that the functio
used to have, but subsequent commits will provide optimised versions for
FLATMEM and SPARSEMEM, and this version will remain for those
architectures which provide their own pfn_valid() implementation,
until/unless they also provide a matching for_each_valid_pfn().
Link: https://lkml.kernel.org/r/20250423133821.789413-1-dwmw2@infradead.org
Link: https://lkml.kernel.org/r/20250423133821.789413-2-dwmw2@infradead.org
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Marc Rutland <mark.rutland@arm.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Ruihan Li <lrh2000@pku.edu.cn>
Cc: Will Deacon <will@kernel.org>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
We introduced KHO into Linux: A framework that allows Linux to pass
metadata and memory across kexec from Linux to Linux. KHO reuses fdt as
file format and shares a lot of the same properties of firmware-to- Linux
boot formats: It needs a stable, documented ABI that allows for forward
and backward compatibility as well as versioning.
As first user of KHO, we introduced memblock which can now preserve memory
ranges reserved with reserve_mem command line options contents across
kexec, so you can use the post-kexec kernel to read traces from the
pre-kexec kernel.
This patch adds memblock schemas similar to "device" device tree ones to a
new kho bindings directory. This allows us to force contributors to
document the data that moves across KHO kexecs and catch breaking change
during review.
Link: https://lkml.kernel.org/r/20250509074635.3187114-18-changyuanl@google.com
Co-developed-by: Alexander Graf <graf@amazon.com>
Signed-off-by: Alexander Graf <graf@amazon.com>
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: Changyuan Lyu <changyuanl@google.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Anthony Yznaga <anthony.yznaga@oracle.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Ashish Kalra <ashish.kalra@amd.com>
Cc: Ben Herrenschmidt <benh@kernel.crashing.org>
Cc: Borislav Betkov <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Gowans <jgowans@amazon.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Krzysztof Kozlowski <krzk@kernel.org>
Cc: Marc Rutland <mark.rutland@arm.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Pratyush Yadav <ptyadav@amazon.de>
Cc: Rob Herring <robh@kernel.org>
Cc: Saravana Kannan <saravanak@google.com>
Cc: Stanislav Kinsburskii <skinsburskii@linux.microsoft.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleinxer <tglx@linutronix.de>
Cc: Thomas Lendacky <thomas.lendacky@amd.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
With KHO in place, let's add documentation that describes what it is and
how to use it.
Link: https://lkml.kernel.org/r/20250509074635.3187114-17-changyuanl@google.com
Signed-off-by: Alexander Graf <graf@amazon.com>
Co-developed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Co-developed-by: Changyuan Lyu <changyuanl@google.com>
Signed-off-by: Changyuan Lyu <changyuanl@google.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Anthony Yznaga <anthony.yznaga@oracle.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Ashish Kalra <ashish.kalra@amd.com>
Cc: Ben Herrenschmidt <benh@kernel.crashing.org>
Cc: Borislav Betkov <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Gowans <jgowans@amazon.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Krzysztof Kozlowski <krzk@kernel.org>
Cc: Marc Rutland <mark.rutland@arm.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Pratyush Yadav <ptyadav@amazon.de>
Cc: Rob Herring <robh@kernel.org>
Cc: Saravana Kannan <saravanak@google.com>
Cc: Stanislav Kinsburskii <skinsburskii@linux.microsoft.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleinxer <tglx@linutronix.de>
Cc: Thomas Lendacky <thomas.lendacky@amd.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Linux has recently gained support for "reserve_mem": A mechanism to
allocate a region of memory early enough in boot that we can cross our
fingers and hope it stays at the same location during most boots, so we
can store for example ftrace buffers into it.
Thanks to KASLR, we can never be really sure that "reserve_mem"
allocations are static across kexec. Let's teach it KHO awareness so that
it serializes its reservations on kexec exit and deserializes them again
on boot, preserving the exact same mapping across kexec.
This is an example user for KHO in the KHO patch set to ensure we have at
least one (not very controversial) user in the tree before extending KHO's
use to more subsystems.
Link: https://lkml.kernel.org/r/20250509074635.3187114-16-changyuanl@google.com
Signed-off-by: Alexander Graf <graf@amazon.com>
Co-developed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Co-developed-by: Changyuan Lyu <changyuanl@google.com>
Signed-off-by: Changyuan Lyu <changyuanl@google.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Anthony Yznaga <anthony.yznaga@oracle.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Ashish Kalra <ashish.kalra@amd.com>
Cc: Ben Herrenschmidt <benh@kernel.crashing.org>
Cc: Borislav Betkov <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Gowans <jgowans@amazon.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Krzysztof Kozlowski <krzk@kernel.org>
Cc: Marc Rutland <mark.rutland@arm.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Pratyush Yadav <ptyadav@amazon.de>
Cc: Rob Herring <robh@kernel.org>
Cc: Saravana Kannan <saravanak@google.com>
Cc: Stanislav Kinsburskii <skinsburskii@linux.microsoft.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleinxer <tglx@linutronix.de>
Cc: Thomas Lendacky <thomas.lendacky@amd.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Add ARCH_SUPPORTS_KEXEC_HANDOVER for 64 bits to allow enabling of
KEXEC_HANDOVER configuration option.
Link: https://lkml.kernel.org/r/20250509074635.3187114-15-changyuanl@google.com
Signed-off-by: Alexander Graf <graf@amazon.com>
Co-developed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Co-developed-by: Changyuan Lyu <changyuanl@google.com>
Signed-off-by: Changyuan Lyu <changyuanl@google.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Anthony Yznaga <anthony.yznaga@oracle.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Ashish Kalra <ashish.kalra@amd.com>
Cc: Ben Herrenschmidt <benh@kernel.crashing.org>
Cc: Borislav Betkov <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Gowans <jgowans@amazon.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Krzysztof Kozlowski <krzk@kernel.org>
Cc: Marc Rutland <mark.rutland@arm.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Pratyush Yadav <ptyadav@amazon.de>
Cc: Rob Herring <robh@kernel.org>
Cc: Saravana Kannan <saravanak@google.com>
Cc: Stanislav Kinsburskii <skinsburskii@linux.microsoft.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleinxer <tglx@linutronix.de>
Cc: Thomas Lendacky <thomas.lendacky@amd.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
During kexec handover (KHO) memory contains data that should be preserved
and this data would be consumed by kexec'ed kernel.
To make sure that the preserved memory is not overwritten, KHO uses
"scratch regions" to bootstrap kexec'ed kernel. These regions are
guaranteed to not have any memory that KHO would preserve and are used as
the only memory the kernel sees during the early boot.
The scratch regions are passed in the setup_data by the first kernel with
other KHO parameters. If the setup_data contains the KHO parameters,
limit randomization to scratch areas only to make sure preserved memory
won't get overwritten.
Since all the pointers in setup_data are represented by u64, they require
double casting (first to unsigned long and then to the actual pointer
type) to compile on 32-bits. This looks goofy out of context, but it is
unfortunately the way that this is handled across the tree. There are at
least a dozen instances of casting like this.
Link: https://lkml.kernel.org/r/20250509074635.3187114-14-changyuanl@google.com
Signed-off-by: Alexander Graf <graf@amazon.com>
Co-developed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Co-developed-by: Changyuan Lyu <changyuanl@google.com>
Signed-off-by: Changyuan Lyu <changyuanl@google.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Anthony Yznaga <anthony.yznaga@oracle.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Ashish Kalra <ashish.kalra@amd.com>
Cc: Ben Herrenschmidt <benh@kernel.crashing.org>
Cc: Borislav Betkov <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Gowans <jgowans@amazon.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Krzysztof Kozlowski <krzk@kernel.org>
Cc: Marc Rutland <mark.rutland@arm.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Pratyush Yadav <ptyadav@amazon.de>
Cc: Rob Herring <robh@kernel.org>
Cc: Saravana Kannan <saravanak@google.com>
Cc: Stanislav Kinsburskii <skinsburskii@linux.microsoft.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleinxer <tglx@linutronix.de>
Cc: Thomas Lendacky <thomas.lendacky@amd.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
KHO kernels are special and use only scratch memory for memblock
allocations, but memory below 1M is ignored by kernel after early boot and
cannot be naturally marked as scratch.
To allow allocation of the real-mode trampoline and a few (if any) other
very early allocations from below 1M forcibly mark the memory below 1M as
scratch.
After real mode trampoline is allocated, clear that scratch marking.
Link: https://lkml.kernel.org/r/20250509074635.3187114-13-changyuanl@google.com
Signed-off-by: Alexander Graf <graf@amazon.com>
Co-developed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Co-developed-by: Changyuan Lyu <changyuanl@google.com>
Signed-off-by: Changyuan Lyu <changyuanl@google.com>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Anthony Yznaga <anthony.yznaga@oracle.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Ashish Kalra <ashish.kalra@amd.com>
Cc: Ben Herrenschmidt <benh@kernel.crashing.org>
Cc: Borislav Betkov <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Gowans <jgowans@amazon.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Krzysztof Kozlowski <krzk@kernel.org>
Cc: Marc Rutland <mark.rutland@arm.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Pratyush Yadav <ptyadav@amazon.de>
Cc: Rob Herring <robh@kernel.org>
Cc: Saravana Kannan <saravanak@google.com>
Cc: Stanislav Kinsburskii <skinsburskii@linux.microsoft.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleinxer <tglx@linutronix.de>
Cc: Thomas Lendacky <thomas.lendacky@amd.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
kexec handover (KHO) creates a metadata that the kernels pass between each
other during kexec. This metadata is stored in memory and kexec image
contains a (physical) pointer to that memory.
In addition, KHO keeps "scratch regions" available for kexec: physically
contiguous memory regions that are guaranteed to not have any memory that
KHO would preserve. The new kernel bootstraps itself using the scratch
regions and sets all handed over memory as in use. When subsystems that
support KHO initialize, they introspect the KHO metadata, restore
preserved memory regions, and retrieve their state stored in the preserved
memory.
Enlighten x86 kexec-file and boot path about the KHO metadata and make
sure it gets passed along to the next kernel.
Link: https://lkml.kernel.org/r/20250509074635.3187114-12-changyuanl@google.com
Signed-off-by: Alexander Graf <graf@amazon.com>
Co-developed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Co-developed-by: Changyuan Lyu <changyuanl@google.com>
Signed-off-by: Changyuan Lyu <changyuanl@google.com>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Anthony Yznaga <anthony.yznaga@oracle.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Ashish Kalra <ashish.kalra@amd.com>
Cc: Ben Herrenschmidt <benh@kernel.crashing.org>
Cc: Borislav Betkov <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Gowans <jgowans@amazon.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Krzysztof Kozlowski <krzk@kernel.org>
Cc: Marc Rutland <mark.rutland@arm.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Pratyush Yadav <ptyadav@amazon.de>
Cc: Rob Herring <robh@kernel.org>
Cc: Saravana Kannan <saravanak@google.com>
Cc: Stanislav Kinsburskii <skinsburskii@linux.microsoft.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleinxer <tglx@linutronix.de>
Cc: Thomas Lendacky <thomas.lendacky@amd.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
memblock_reserve() does not distinguish memory used by firmware from
memory used by kernel.
The distinction is nice to have for accounting of early memory allocations
and reservations, but it is essential for kexec handover (kho) to know how
much memory kernel consumes during boot.
Use memblock_reserve_kern() to reserve kernel memory, such as kernel
image, initrd and setup data.
Link: https://lkml.kernel.org/r/20250509074635.3187114-11-changyuanl@google.com
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: Changyuan Lyu <changyuanl@google.com>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Alexander Graf <graf@amazon.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Anthony Yznaga <anthony.yznaga@oracle.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Ashish Kalra <ashish.kalra@amd.com>
Cc: Ben Herrenschmidt <benh@kernel.crashing.org>
Cc: Borislav Betkov <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Gowans <jgowans@amazon.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Krzysztof Kozlowski <krzk@kernel.org>
Cc: Marc Rutland <mark.rutland@arm.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Pratyush Yadav <ptyadav@amazon.de>
Cc: Rob Herring <robh@kernel.org>
Cc: Saravana Kannan <saravanak@google.com>
Cc: Stanislav Kinsburskii <skinsburskii@linux.microsoft.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleinxer <tglx@linutronix.de>
Cc: Thomas Lendacky <thomas.lendacky@amd.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
We now have all bits in place to support KHO kexecs. Add awareness of KHO
in the kexec file as well as boot path for arm64 and adds the respective
kconfig option to the architecture so that it can use KHO successfully.
Changes to the "chosen" node have been sent to
https://github.com/devicetree-org/dt-schema/pull/158.
Link: https://lkml.kernel.org/r/20250509074635.3187114-10-changyuanl@google.com
Signed-off-by: Alexander Graf <graf@amazon.com>
Co-developed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Co-developed-by: Changyuan Lyu <changyuanl@google.com>
Signed-off-by: Changyuan Lyu <changyuanl@google.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Anthony Yznaga <anthony.yznaga@oracle.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Ashish Kalra <ashish.kalra@amd.com>
Cc: Ben Herrenschmidt <benh@kernel.crashing.org>
Cc: Borislav Betkov <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Gowans <jgowans@amazon.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Krzysztof Kozlowski <krzk@kernel.org>
Cc: Marc Rutland <mark.rutland@arm.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Pratyush Yadav <ptyadav@amazon.de>
Cc: Rob Herring <robh@kernel.org>
Cc: Saravana Kannan <saravanak@google.com>
Cc: Stanislav Kinsburskii <skinsburskii@linux.microsoft.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleinxer <tglx@linutronix.de>
Cc: Thomas Lendacky <thomas.lendacky@amd.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
We have all generic code in place now to support Kexec with KHO. This
patch adds a config option that depends on architecture support to enable
KHO support.
Link: https://lkml.kernel.org/r/20250509074635.3187114-9-changyuanl@google.com
Signed-off-by: Alexander Graf <graf@amazon.com>
Co-developed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: Changyuan Lyu <changyuanl@google.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Anthony Yznaga <anthony.yznaga@oracle.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Ashish Kalra <ashish.kalra@amd.com>
Cc: Ben Herrenschmidt <benh@kernel.crashing.org>
Cc: Borislav Betkov <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Gowans <jgowans@amazon.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Krzysztof Kozlowski <krzk@kernel.org>
Cc: Marc Rutland <mark.rutland@arm.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Pratyush Yadav <ptyadav@amazon.de>
Cc: Rob Herring <robh@kernel.org>
Cc: Saravana Kannan <saravanak@google.com>
Cc: Stanislav Kinsburskii <skinsburskii@linux.microsoft.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleinxer <tglx@linutronix.de>
Cc: Thomas Lendacky <thomas.lendacky@amd.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Kexec has 2 modes: A user space driven mode and a kernel driven mode. For
the kernel driven mode, kernel code determines the physical addresses of
all target buffers that the payload gets copied into.
With KHO, we can only safely copy payloads into the "scratch area". Teach
the kexec file loader about it, so it only allocates for that area. In
addition, enlighten it with support to ask the KHO subsystem for its
respective payloads to copy into target memory. Also teach the KHO
subsystem how to fill the images for file loads.
Link: https://lkml.kernel.org/r/20250509074635.3187114-8-changyuanl@google.com
Signed-off-by: Alexander Graf <graf@amazon.com>
Co-developed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Co-developed-by: Changyuan Lyu <changyuanl@google.com>
Signed-off-by: Changyuan Lyu <changyuanl@google.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Anthony Yznaga <anthony.yznaga@oracle.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Ashish Kalra <ashish.kalra@amd.com>
Cc: Ben Herrenschmidt <benh@kernel.crashing.org>
Cc: Borislav Betkov <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Gowans <jgowans@amazon.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Krzysztof Kozlowski <krzk@kernel.org>
Cc: Marc Rutland <mark.rutland@arm.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Pratyush Yadav <ptyadav@amazon.de>
Cc: Rob Herring <robh@kernel.org>
Cc: Saravana Kannan <saravanak@google.com>
Cc: Stanislav Kinsburskii <skinsburskii@linux.microsoft.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleinxer <tglx@linutronix.de>
Cc: Thomas Lendacky <thomas.lendacky@amd.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Introduce APIs allowing KHO users to preserve memory across kexec and get
access to that memory after boot of the kexeced kernel
kho_preserve_folio() - record a folio to be preserved over kexec
kho_restore_folio() - recreates the folio from the preserved memory
kho_preserve_phys() - record physically contiguous range to be
preserved over kexec.
The memory preservations are tracked by two levels of xarrays to manage
chunks of per-order 512 byte bitmaps. For instance if PAGE_SIZE = 4096,
the entire 1G order of a 1TB x86 system would fit inside a single 512 byte
bitmap. For order 0 allocations each bitmap will cover 16M of address
space. Thus, for 16G of memory at most 512K of bitmap memory will be
needed for order 0.
At serialization time all bitmaps are recorded in a linked list of pages
for the next kernel to process and the physical address of the list is
recorded in KHO FDT.
The next kernel then processes that list, reserves the memory ranges and
later, when a user requests a folio or a physical range, KHO restores
corresponding memory map entries.
Link: https://lkml.kernel.org/r/20250509074635.3187114-7-changyuanl@google.com
Suggested-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Co-developed-by: Changyuan Lyu <changyuanl@google.com>
Signed-off-by: Changyuan Lyu <changyuanl@google.com>
Cc: Alexander Graf <graf@amazon.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Anthony Yznaga <anthony.yznaga@oracle.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Ashish Kalra <ashish.kalra@amd.com>
Cc: Ben Herrenschmidt <benh@kernel.crashing.org>
Cc: Borislav Betkov <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Gowans <jgowans@amazon.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Krzysztof Kozlowski <krzk@kernel.org>
Cc: Marc Rutland <mark.rutland@arm.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Pratyush Yadav <ptyadav@amazon.de>
Cc: Rob Herring <robh@kernel.org>
Cc: Saravana Kannan <saravanak@google.com>
Cc: Stanislav Kinsburskii <skinsburskii@linux.microsoft.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleinxer <tglx@linutronix.de>
Cc: Thomas Lendacky <thomas.lendacky@amd.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
When we have a KHO kexec, we get an FDT blob and scratch region to
populate the state of the system. Provide helper functions that allow
architecture code to easily handle memory reservations based on them and
give device drivers visibility into the KHO FDT and memory reservations so
they can recover their own state.
Include a fix from Arnd Bergmann <arnd@arndb.de>
https://lore.kernel.org/lkml/20250424093302.3894961-1-arnd@kernel.org/.
Link: https://lkml.kernel.org/r/20250509074635.3187114-6-changyuanl@google.com
Signed-off-by: Alexander Graf <graf@amazon.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Co-developed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Co-developed-by: Changyuan Lyu <changyuanl@google.com>
Signed-off-by: Changyuan Lyu <changyuanl@google.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Anthony Yznaga <anthony.yznaga@oracle.com>
Cc: Ashish Kalra <ashish.kalra@amd.com>
Cc: Ben Herrenschmidt <benh@kernel.crashing.org>
Cc: Borislav Betkov <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Gowans <jgowans@amazon.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Krzysztof Kozlowski <krzk@kernel.org>
Cc: Marc Rutland <mark.rutland@arm.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Pratyush Yadav <ptyadav@amazon.de>
Cc: Rob Herring <robh@kernel.org>
Cc: Saravana Kannan <saravanak@google.com>
Cc: Stanislav Kinsburskii <skinsburskii@linux.microsoft.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleinxer <tglx@linutronix.de>
Cc: Thomas Lendacky <thomas.lendacky@amd.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Add the infrastructure to generate Kexec HandOver metadata. Kexec
HandOver is a mechanism that allows Linux to preserve state - arbitrary
properties as well as memory locations - across kexec.
It does so using 2 concepts:
1) KHO FDT - Every KHO kexec carries a KHO specific flattened device tree
blob that describes preserved memory regions. Device drivers can
register to KHO to serialize and preserve their states before kexec.
2) Scratch Regions - CMA regions that we allocate in the first kernel.
CMA gives us the guarantee that no handover pages land in those
regions, because handover pages must be at a static physical memory
location. We use these regions as the place to load future kexec
images so that they won't collide with any handover data.
Link: https://lkml.kernel.org/r/20250509074635.3187114-5-changyuanl@google.com
Signed-off-by: Alexander Graf <graf@amazon.com>
Co-developed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Co-developed-by: Pratyush Yadav <ptyadav@amazon.de>
Signed-off-by: Pratyush Yadav <ptyadav@amazon.de>
Co-developed-by: Changyuan Lyu <changyuanl@google.com>
Signed-off-by: Changyuan Lyu <changyuanl@google.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Anthony Yznaga <anthony.yznaga@oracle.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Ashish Kalra <ashish.kalra@amd.com>
Cc: Ben Herrenschmidt <benh@kernel.crashing.org>
Cc: Borislav Betkov <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Gowans <jgowans@amazon.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Krzysztof Kozlowski <krzk@kernel.org>
Cc: Marc Rutland <mark.rutland@arm.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rob Herring <robh@kernel.org>
Cc: Saravana Kannan <saravanak@google.com>
Cc: Stanislav Kinsburskii <skinsburskii@linux.microsoft.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleinxer <tglx@linutronix.de>
Cc: Thomas Lendacky <thomas.lendacky@amd.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
With deferred initialization of struct page it will be necessary to
initialize memory map for KHO scratch regions early.
Add memmap_init_kho_scratch() method that will allow such initialization
in upcoming patches.
Link: https://lkml.kernel.org/r/20250509074635.3187114-4-changyuanl@google.com
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: Changyuan Lyu <changyuanl@google.com>
Cc: Alexander Graf <graf@amazon.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Anthony Yznaga <anthony.yznaga@oracle.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Ashish Kalra <ashish.kalra@amd.com>
Cc: Ben Herrenschmidt <benh@kernel.crashing.org>
Cc: Borislav Betkov <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Gowans <jgowans@amazon.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Krzysztof Kozlowski <krzk@kernel.org>
Cc: Marc Rutland <mark.rutland@arm.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Pratyush Yadav <ptyadav@amazon.de>
Cc: Rob Herring <robh@kernel.org>
Cc: Saravana Kannan <saravanak@google.com>
Cc: Stanislav Kinsburskii <skinsburskii@linux.microsoft.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleinxer <tglx@linutronix.de>
Cc: Thomas Lendacky <thomas.lendacky@amd.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
With KHO (Kexec HandOver), we need a way to ensure that the new kernel
does not allocate memory on top of any memory regions that the previous
kernel was handing over. But to know where those are, we need to include
them in the memblock.reserved array which may not be big enough to hold
all ranges that need to be persisted across kexec. To resize the array,
we need to allocate memory. That brings us into a catch 22 situation.
The solution to that is limit memblock allocations to the scratch regions:
safe regions to operate in the case when there is memory that should
remain intact across kexec.
KHO provides several "scratch regions" as part of its metadata. These
scratch regions are contiguous memory blocks that known not to contain any
memory that should be persisted across kexec. These regions should be
large enough to accommodate all memblock allocations done by the kexeced
kernel.
We introduce a new memblock_set_scratch_only() function that allows KHO to
indicate that any memblock allocation must happen from the scratch
regions.
Later, we may want to perform another KHO kexec. For that, we reuse the
same scratch regions. To ensure that no eventually handed over data gets
allocated inside a scratch region, we flip the semantics of the scratch
region with memblock_clear_scratch_only(): After that call, no allocations
may happen from scratch memblock regions. We will lift that restriction
in the next patch.
Link: https://lkml.kernel.org/r/20250509074635.3187114-3-changyuanl@google.com
Signed-off-by: Alexander Graf <graf@amazon.com>
Co-developed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: Changyuan Lyu <changyuanl@google.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Anthony Yznaga <anthony.yznaga@oracle.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Ashish Kalra <ashish.kalra@amd.com>
Cc: Ben Herrenschmidt <benh@kernel.crashing.org>
Cc: Borislav Betkov <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Gowans <jgowans@amazon.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Krzysztof Kozlowski <krzk@kernel.org>
Cc: Marc Rutland <mark.rutland@arm.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Pratyush Yadav <ptyadav@amazon.de>
Cc: Rob Herring <robh@kernel.org>
Cc: Saravana Kannan <saravanak@google.com>
Cc: Stanislav Kinsburskii <skinsburskii@linux.microsoft.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleinxer <tglx@linutronix.de>
Cc: Thomas Lendacky <thomas.lendacky@amd.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
|
|
Patch series "kexec: introduce Kexec HandOver (KHO)", v8.
Kexec today considers itself purely a boot loader: When we enter the new
kernel, any state the previous kernel left behind is irrelevant and the
new kernel reinitializes the system.
However, there are use cases where this mode of operation is not what we
actually want. In virtualization hosts for example, we want to use kexec
to update the host kernel while virtual machine memory stays untouched.
When we add device assignment to the mix, we also need to ensure that
IOMMU and VFIO states are untouched. If we add PCIe peer to peer DMA, we
need to do the same for the PCI subsystem. If we want to kexec while an
SEV-SNP enabled virtual machine is running, we need to preserve the VM
context pages and physical memory. See "pkernfs: Persisting guest memory
and kernel/device state safely across kexec" Linux Plumbers Conference
2023 presentation for details:
https://lpc.events/event/17/contributions/1485/
To start us on the journey to support all the use cases above, this patch
implements basic infrastructure to allow hand over of kernel state across
kexec (Kexec HandOver, aka KHO). As a really simple example target, we
use memblock's reserve_mem.
With this patchset applied, memory that was reserved using "reserve_mem"
command line options remains intact after kexec and it is guaranteed to
reside at the same physical address.
== Alternatives ==
There are alternative approaches to (parts of) the problems above:
* Memory Pools [1] - preallocated persistent memory region + allocator
* PRMEM [2] - resizable persistent memory regions with fixed metadata
pointer on the kernel command line + allocator
* Pkernfs [3] - preallocated file system for in-kernel data with fixed
address location on the kernel command line
* PKRAM [4] - handover of user space pages using a fixed metadata page
specified via command line
All of the approaches above fundamentally have the same problem: They
require the administrator to explicitly carve out a physical memory
location because they have no mechanism outside of the kernel command line
to pass data (including memory reservations) between kexec'ing kernels.
KHO provides that base foundation. We will determine later whether we
still need any of the approaches above for fast bulk memory handover of
for example IOMMU page tables. But IMHO they would all be users of KHO,
with KHO providing the foundational primitive to pass metadata and bulk
memory reservations as well as provide easy versioning for data.
== Overview ==
We introduce a metadata file that the kernels pass between each other.
How they pass it is architecture specific. The file's format is a
Flattened Device Tree (fdt) which has a generator and parser already
included in Linux. KHO is enabled in the kernel command line by `kho=on`.
When the root user enables KHO through
/sys/kernel/debug/kho/out/finalize, the kernel invokes callbacks to every
KHO users to register preserved memory regions, which contain drivers'
states.
When the actual kexec happens, the fdt is part of the image set that we
boot into. In addition, we keep "scratch regions" available for kexec:
physically contiguous memory regions that are guaranteed to not have any
memory that KHO would preserve. The new kernel bootstraps itself using
the scratch regions and sets all handed over memory as in use. When
drivers initialize that support KHO, they introspect the fdt, restore
preserved memory regions, and retrieve their states stored in the
preserved memory.
== Limitations ==
Currently KHO is only implemented for file based kexec. The kernel
interfaces in the patch set are already in place to support user space
kexec as well, but it is still not implemented it yet inside kexec tools.
== How to Use ==
To use the code, please boot the kernel with the "kho=on" command line
parameter. KHO will automatically create scratch regions. If you want to
set the scratch size explicitly you can use "kho_scratch=" command line
parameter. For instance, "kho_scratch=16M,512M,256M" will reserve a 16
MiB low memory scratch area, a 512 MiB global scratch region, and 256 MiB
per NUMA node scratch regions on boot.
Make sure to have a reserved memory range requested with reserv_mem
command line option, for example, "reserve_mem=64m:4k:n1".
Then before you invoke file based "kexec -l", finalize KHO FDT:
# echo 1 > /sys/kernel/debug/kho/out/finalize
You can preview the generated FDT using `dtc`,
# dtc /sys/kernel/debug/kho/out/fdt
# dtc /sys/kernel/debug/kho/out/sub_fdts/memblock
`dtc` is available on ubuntu by `sudo apt-get install device-tree-compiler`.
Now kexec into the new kernel,
# kexec -l Image --initrd=initrd -s
# kexec -e
(The order of KHO finalization and "kexec -l" does not matter.)
The new kernel will boot up and contain the previous kernel's reserve_mem
contents at the same physical address as the first kernel.
You can also review the FDT passed from the old kernel,
# dtc /sys/kernel/debug/kho/in/fdt
# dtc /sys/kernel/debug/kho/in/sub_fdts/memblock
This patch (of 17):
To denote areas that were reserved for kernel use either directly with
memblock_reserve_kern() or via memblock allocations.
Link: https://lore.kernel.org/lkml/20250424083258.2228122-1-changyuanl@google.com/
Link: https://lore.kernel.org/lkml/aAeaJ2iqkrv_ffhT@kernel.org/
Link: https://lore.kernel.org/lkml/35c58191-f774-40cf-8d66-d1e2aaf11a62@intel.com/
Link: https://lore.kernel.org/lkml/20250424093302.3894961-1-arnd@kernel.org/
Link: https://lkml.kernel.org/r/20250509074635.3187114-1-changyuanl@google.com
Link: https://lkml.kernel.org/r/20250509074635.3187114-2-changyuanl@google.com
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Co-developed-by: Changyuan Lyu <changyuanl@google.com>
Signed-off-by: Changyuan Lyu <changyuanl@google.com>
Cc: Alexander Graf <graf@amazon.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Anthony Yznaga <anthony.yznaga@oracle.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Ashish Kalra <ashish.kalra@amd.com>
Cc: Ben Herrenschmidt <benh@kernel.crashing.org>
Cc: Borislav Betkov <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Gowans <jgowans@amazon.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Krzysztof Kozlowski <krzk@kernel.org>
Cc: Marc Rutland <mark.rutland@arm.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Pratyush Yadav <ptyadav@amazon.de>
Cc: Rob Herring <robh@kernel.org>
Cc: Saravana Kannan <saravanak@google.com>
Cc: Stanislav Kinsburskii <skinsburskii@linux.microsoft.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleinxer <tglx@linutronix.de>
Cc: Thomas Lendacky <thomas.lendacky@amd.com>
Cc: Will Deacon <will@kernel.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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The trace functions trace_mm_collapse_huge_page_isolate() and
trace_mm_khugepaged_scan_pmd() each have a single user, which always
passes in the head page of a folio. Refactor both functions to take a
folio directly.
Link: https://lkml.kernel.org/r/20250425002425.533698-1-nifan.cxl@gmail.com
Signed-off-by: Fan Ni <fan.ni@samsung.com>
Reviewed-by: Nico Pache <npache@redhat.com>
Reviewed-by: Davidlohr Bueso <dave@stgolabs.net>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: Yang Shi <yang@os.amperecomputing.com>
Acked-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Adam Manzanares <a.manzanares@samsung.com>
Cc: Luis Chamberalin <mcgrof@kernel.org>
Cc: Mariano Pache <npache@redhat.com>
Cc: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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The temporary local variable 'nd' is redundant. Directly assign the
virtual address to node_data[nid] to simplify the code.
No functional change.
Link: https://lkml.kernel.org/r/20250427100442.958352-4-ye.liu@linux.dev
Signed-off-by: Ye Liu <liuye@kylinos.cn>
Acked-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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When an invalid debug_guardpage_minorder value is provided, include the
user input in the error message. This helps users and developers diagnose
configuration issues more easily.
No functional change.
Link: https://lkml.kernel.org/r/20250427100442.958352-3-ye.liu@linux.dev
Signed-off-by: Ye Liu <liuye@kylinos.cn>
Acked-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Patch series "mm: small cleanups for io-mapping, debug_page_alloc and
numa".
This series includes three small cleanups to mm/:
- io-mapping: simplify remap protection flag calculation
- debug_page_alloc: improve error message by printing invalid input
- numa: remove unnecessary variable for clarity
No functional changes.
This patch (of 3):
In io_mapping_map_user(), precompute the page protection flags in a local
variable before calling remap_pfn_range_notrack().
No functional change.
Link: https://lkml.kernel.org/r/20250427100442.958352-1-ye.liu@linux.dev
Link: https://lkml.kernel.org/r/20250427100442.958352-2-ye.liu@linux.dev
Signed-off-by: Ye Liu <liuye@kylinos.cn>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Change the type of 'dwRegionSize' in wp_init() and wp_free() from int to
long to match callers that pass long or unsigned long long values.
wp_addr_range function is left unchanged because it passes 'dwRegionSize'
parameter directly to pagemap_ioctl, which expects an int.
This patch does not fix any actual known issues. It aligns parameter
types with their actual usage and avoids any potential future issues.
Link: https://lkml.kernel.org/r/20250427102639.39978-1-siddarthsgml@gmail.com
Signed-off-by: Siddarth G <siddarthsgml@gmail.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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The macro INIT_PASID was originally used by mm_init_pasid. However, since
commit a6cbd44093ef ("kernel/fork: Initialize mm's PASID"), mm_init_pasid
has been removed. Therefore, INIT_PASID is no longer needed and is
removed.
Link: https://lkml.kernel.org/r/20250427145004.13049-1-hank20010209@gmail.com
Signed-off-by: Cheng-Han Wu <hank20010209@gmail.com>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Fix a minor typo in the comment above page_address_in_vma():
"responsibililty" → "responsibility"
Link: https://lkml.kernel.org/r/20250421085729.127845-3-ye.liu@linux.dev
Signed-off-by: Ye Liu <liuye@kylinos.cn>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reviewed-by: Harry Yoo <harry.yoo@oracle.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Naoya Horiguchi <nao.horiguchi@gmail.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Patch series "mm: minor cleanups in rmap", v3.
Minor cleanups in mm/rmap.c:
- Rename a local variable for consistency
- Fix a typo in a comment
No functional changes.
This patch (of 2):
Rename local variable page__anon_vma in page_address_in_vma() to anon_vma.
The previous naming convention of using double underscores (__) is
unnecessary and inconsistent with typical kernel style, which uses single
underscores to denote local variables. Also updated comments to reflect
the new variable name.
Functionality unchanged.
Link: https://lkml.kernel.org/r/20250421085729.127845-1-ye.liu@linux.dev
Link: https://lkml.kernel.org/r/20250421085729.127845-2-ye.liu@linux.dev
Signed-off-by: Ye Liu <liuye@kylinos.cn>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Acked-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Harry Yoo <harry.yoo@oracle.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Liu Ye <liuye@kylinos.cn>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Naoya Horiguchi <nao.horiguchi@gmail.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Using SWAPPINESS_ANON_ONLY instead of MAX_SWAPPINESS + 1 to indicate
reclaiming only from anonymous pages makes the code more readable and
explicit.
Add some comment in the SWAPPINESS_ANON_ONLY context.
Link: https://lkml.kernel.org/r/529db7ae6098ee712b81e4df290622e4e64ac50c.1745225696.git.hezhongkun.hzk@bytedance.com
Signed-off-by: Zhongkun He <hezhongkun.hzk@bytedance.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Yosry Ahmed <yosry.ahmed@linux.dev>
Cc: Yu Zhao <yuzhao@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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The MGLRU already supports reclaiming only from anonymous memory via the
/sys/kernel/debug/lru_gen interface. Now, memory.reclaim also supports
the swappiness=max parameter to enable reclaiming solely from anonymous
memory. To unify the semantics of proactive reclaiming from anonymous
folios, the max parameter is introduced.
[hezhongkun.hzk@bytedance.com: use strcmp instead of strncmp, if swappiness is not set, use the default value]
Link: https://lkml.kernel.org/r/20250507071057.3184240-1-hezhongkun.hzk@bytedance.com
[akpm@linux-foundation.org: tweak coding style]
Link: https://lkml.kernel.org/r/65181f7745d657d664d833c26d8a94cae40538b9.1745225696.git.hezhongkun.hzk@bytedance.com
Signed-off-by: Zhongkun He <hezhongkun.hzk@bytedance.com>
Acked-by: Muchun Song <muchun.song@linux.dev>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Yosry Ahmed <yosry.ahmed@linux.dev>
Cc: Yu Zhao <yuzhao@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Add more comments for cache_trim_mode, and the annotations provided by
Johannes Weiner in [1].
Link: https://lore.kernel.org/all/20250314141833.GA1316033@cmpxchg.org/
Link: https://lkml.kernel.org/r/4baad87ba637f1e6f666e9b99b3fdcb7ab39171b.1745225696.git.hezhongkun.hzk@bytedance.com
Signed-off-by: Zhongkun He <hezhongkun.hzk@bytedance.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Yosry Ahmed <yosry.ahmed@linux.dev>
Cc: Yu Zhao <yuzhao@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Patch series "add max arg to swappiness in memory.reclaim and lru_gen", v4.
This patchset adds max arg to swappiness in memory.reclaim and lru_gen for
anon only proactive memory reclaim.
With commit <68cd9050d871> ("mm: add swappiness= arg to memory.reclaim")
we can submit an additional swappiness=<val> argument to memory.reclaim.
It is very useful because we can dynamically adjust the reclamation ratio
based on the anonymous folios and file folios of each cgroup. For
example,when swappiness is set to 0, we only reclaim from file folios.
But we can not relciam memory just from anon folios.
This patchset introduces a new macro, SWAPPINESS_ANON_ONLY, defined as
MAX_SWAPPINESS + 1, represent the max arg semantics. It specifically
indicates that reclamation should occur only from anonymous pages.
Patch 1 adds swappiness=max arg to memory.reclaim suggested-by: Yosry
Ahmed
Patch 2 add more comments for cache_trim_mode from Johannes Weiner in [1].
Patch 3 add max arg to lru_gen for proactive memory reclaim in MGLRU. The
MGLRU already supports reclaiming exclusively from anonymous pages. This
patch formalizes that behavior by introducing a max parameter to represent
the corresponding semantics.
Patch 4 using SWAPPINESS_ANON_ONLY in MGLRU Using SWAPPINESS_ANON_ONLY
instead of MAX_SWAPPINESS + 1 to indicate reclaiming only from anonymous
pages makes the code more readable and explicit
Here is the previous discussion:
https://lore.kernel.org/all/20250314033350.1156370-1-hezhongkun.hzk@bytedance.com/
https://lore.kernel.org/all/20250312094337.2296278-1-hezhongkun.hzk@bytedance.com/
https://lore.kernel.org/all/20250318135330.3358345-1-hezhongkun.hzk@bytedance.com/
This patch (of 4):
With commit <68cd9050d871> ("mm: add swappiness= arg to memory.reclaim")
we can submit an additional swappiness=<val> argument to memory.reclaim.
It is very useful because we can dynamically adjust the reclamation ratio
based on the anonymous folios and file folios of each cgroup. For
example,when swappiness is set to 0, we only reclaim from file folios.
However,we have also encountered a new issue: when swappiness is set to
the MAX_SWAPPINESS, it may still only reclaim file folios.
So, we hope to add a new arg 'swappiness=max' in memory.reclaim where
proactive memory reclaim only reclaims from anonymous folios when
swappiness is set to max. The swappiness semantics from a user
perspective remain unchanged.
For example, something like this:
echo "2M swappiness=max" > /sys/fs/cgroup/memory.reclaim
will perform reclaim on the rootcg with a swappiness setting of 'max' (a
new mode) regardless of the file folios. Users have a more comprehensive
view of the application's memory distribution because there are many
metrics available. For example, if we find that a certain cgroup has a
large number of inactive anon folios, we can reclaim only those and skip
file folios, because with the zram/zswap, the IO tradeoff that
cache_trim_mode or other file first logic is making doesn't hold - file
refaults will cause IO, whereas anon decompression will not.
With this patch, the swappiness argument of memory.reclaim has a new
mode 'max', means reclaiming just from anonymous folios both in traditional
LRU and MGLRU.
Link: https://lkml.kernel.org/r/cover.1745225696.git.hezhongkun.hzk@bytedance.com
Link: https://lore.kernel.org/all/20250314141833.GA1316033@cmpxchg.org/ [1]
Link: https://lkml.kernel.org/r/519e12b9b1f8c31a01e228c8b4b91a2419684f77.1745225696.git.hezhongkun.hzk@bytedance.com
Signed-off-by: Zhongkun He <hezhongkun.hzk@bytedance.com>
Suggested-by: Yosry Ahmed <yosry.ahmed@linux.dev>
Acked-by: Muchun Song <muchun.song@linux.dev>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Yu Zhao <yuzhao@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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add more explanation in doc and commit message on O_NONBLOCK side-effects
(Johannes)
Link: https://lkml.kernel.org/r/20250506232833.3109790-1-shakeel.butt@linux.dev
Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev>
Acked-by: Roman Gushchin <roman.gushchin@linux.dev>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Greg Thelen <gthelen@google.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Michal Koutný <mkoutny@suse.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Tejun Heo <tj@kernel.org>
Cc: Yosry Ahmed <yosry.ahmed@linux.dev>
Cc: Christian Brauner <brauner@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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