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2021-10-01KVM: x86/mmu: Avoid memslot lookup in make_spte and mmu_try_to_unsync_pagesDavid Matlack
mmu_try_to_unsync_pages checks if page tracking is active for the given gfn, which requires knowing the memslot. We can pass down the memslot via make_spte to avoid this lookup. The memslot is also handy for make_spte's marking of the gfn as dirty: we can test whether dirty page tracking is enabled, and if so ensure that pages are mapped as writable with 4K granularity. Apart from the warning, no functional change is intended. Signed-off-by: David Matlack <dmatlack@google.com> Message-Id: <20210813203504.2742757-7-dmatlack@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-10-01KVM: x86/mmu: Avoid memslot lookup in rmap_addDavid Matlack
Avoid the memslot lookup in rmap_add, by passing it down from the fault handling code to mmu_set_spte and then to rmap_add. No functional change intended. Signed-off-by: David Matlack <dmatlack@google.com> Message-Id: <20210813203504.2742757-6-dmatlack@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-10-01KVM: MMU: pass struct kvm_page_fault to mmu_set_sptePaolo Bonzini
mmu_set_spte is called for either PTE prefetching or page faults. The three boolean arguments write_fault, speculative and host_writable are always respectively false/true/true for prefetching and coming from a struct kvm_page_fault for page faults. Let mmu_set_spte distinguish these two situation by accepting a possibly NULL struct kvm_page_fault argument. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-10-01KVM: MMU: pass kvm_mmu_page struct to make_sptePaolo Bonzini
The level and A/D bit support of the new SPTE can be found in the role, which is stored in the kvm_mmu_page struct. This merges two arguments into one. For the TDP MMU, the kvm_mmu_page was not used (kvm_tdp_mmu_map does not use it if the SPTE is already present) so we fetch it just before calling make_spte. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-10-01KVM: MMU: set ad_disabled in TDP MMU rolePaolo Bonzini
Prepare for removing the ad_disabled argument of make_spte; instead it can be found in the role of a struct kvm_mmu_page. First of all, the TDP MMU must set the role accurately. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-10-01KVM: MMU: remove unnecessary argument to mmu_set_sptePaolo Bonzini
The level of the new SPTE can be found in the kvm_mmu_page struct; there is no need to pass it down. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-10-01KVM: MMU: clean up make_spte return valuePaolo Bonzini
Now that make_spte is called directly by the shadow MMU (rather than wrapped by set_spte), it only has to return one boolean value. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-10-01KVM: MMU: inline set_spte in FNAME(sync_page)Paolo Bonzini
Since the two callers of set_spte do different things with the results, inlining it actually makes the code simpler to reason about. For example, FNAME(sync_page) already has a struct kvm_mmu_page *, but set_spte had to fish it back out of sptep's private page data. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-10-01KVM: MMU: inline set_spte in mmu_set_sptePaolo Bonzini
Since the two callers of set_spte do different things with the results, inlining it actually makes the code simpler to reason about. For example, mmu_set_spte looks quite like tdp_mmu_map_handle_target_level, but the similarity is hidden by set_spte. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-10-01KVM: x86/mmu: Avoid memslot lookup in page_fault_handle_page_trackDavid Matlack
Now that kvm_page_fault has a pointer to the memslot it can be passed down to the page tracking code to avoid a redundant slot lookup. No functional change intended. Signed-off-by: David Matlack <dmatlack@google.com> Message-Id: <20210813203504.2742757-5-dmatlack@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-10-01KVM: x86/mmu: Pass the memslot around via struct kvm_page_faultDavid Matlack
The memslot for the faulting gfn is used throughout the page fault handling code, so capture it in kvm_page_fault as soon as we know the gfn and use it in the page fault handling code that has direct access to the kvm_page_fault struct. Replace various tests using is_noslot_pfn with more direct tests on fault->slot being NULL. This, in combination with the subsequent patch, improves "Populate memory time" in dirty_log_perf_test by 5% when using the legacy MMU. There is no discerable improvement to the performance of the TDP MMU. No functional change intended. Suggested-by: Ben Gardon <bgardon@google.com> Signed-off-by: David Matlack <dmatlack@google.com> Message-Id: <20210813203504.2742757-4-dmatlack@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-10-01KVM: MMU: unify tdp_mmu_map_set_spte_atomic and ↵Paolo Bonzini
tdp_mmu_set_spte_atomic_no_dirty_log tdp_mmu_map_set_spte_atomic is not taking care of dirty logging anymore, the only difference that remains is that it takes a vCPU instead of the struct kvm. Merge the two functions. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-10-01KVM: MMU: mark page dirty in make_sptePaolo Bonzini
This simplifies set_spte, which we want to remove, and unifies code between the shadow MMU and the TDP MMU. The warning will be added back later to make_spte as well. There is a small disadvantage in the TDP MMU; it may unnecessarily mark a page as dirty twice if two vCPUs end up mapping the same page twice. However, this is a very small cost for a case that is already rare. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-10-01KVM: x86/mmu: Fold rmap_recycle into rmap_addDavid Matlack
Consolidate rmap_recycle and rmap_add into a single function since they are only ever called together (and only from one place). This has a nice side effect of eliminating an extra kvm_vcpu_gfn_to_memslot(). In addition it makes mmu_set_spte(), which is a very long function, a little shorter. No functional change intended. Signed-off-by: David Matlack <dmatlack@google.com> Message-Id: <20210813203504.2742757-3-dmatlack@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-10-01KVM: x86/mmu: Verify shadow walk doesn't terminate early in page faultsSean Christopherson
WARN and bail if the shadow walk for faulting in a SPTE terminates early, i.e. doesn't reach the expected level because the walk encountered a terminal SPTE. The shadow walks for page faults are subtle in that they install non-leaf SPTEs (zapping leaf SPTEs if necessary!) in the loop body, and consume the newly created non-leaf SPTE in the loop control, e.g. __shadow_walk_next(). In other words, the walks guarantee that the walk will stop if and only if the target level is reached by installing non-leaf SPTEs to guarantee the walk remains valid. Opportunistically use fault->goal-level instead of it.level in FNAME(fetch) to further clarify that KVM always installs the leaf SPTE at the target level. Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com> Signed-off-by: Sean Christopherson <seanjc@google.com> Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com> Message-Id: <20210906122547.263316-1-jiangshanlai@gmail.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-10-01KVM: MMU: change tracepoints arguments to kvm_page_faultPaolo Bonzini
Pass struct kvm_page_fault to tracepoints instead of extracting the arguments from the struct. This also lets the kvm_mmu_spte_requested tracepoint pick the gfn directly from fault->gfn, instead of using the address. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-10-01KVM: MMU: change disallowed_hugepage_adjust() arguments to kvm_page_faultPaolo Bonzini
Pass struct kvm_page_fault to disallowed_hugepage_adjust() instead of extracting the arguments from the struct. Tweak a bit the conditions to avoid long lines. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-10-01KVM: MMU: change kvm_mmu_hugepage_adjust() arguments to kvm_page_faultPaolo Bonzini
Pass struct kvm_page_fault to kvm_mmu_hugepage_adjust() instead of extracting the arguments from the struct; the results are also stored in the struct, so the callers are adjusted consequently. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-10-01KVM: MMU: change fast_page_fault() arguments to kvm_page_faultPaolo Bonzini
Pass struct kvm_page_fault to fast_page_fault() instead of extracting the arguments from the struct. Suggested-by: Isaku Yamahata <isaku.yamahata@intel.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-10-01KVM: MMU: change tdp_mmu_map_handle_target_level() arguments to kvm_page_faultPaolo Bonzini
Pass struct kvm_page_fault to tdp_mmu_map_handle_target_level() instead of extracting the arguments from the struct. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-10-01KVM: MMU: change kvm_tdp_mmu_map() arguments to kvm_page_faultPaolo Bonzini
Pass struct kvm_page_fault to kvm_tdp_mmu_map() instead of extracting the arguments from the struct. Suggested-by: Isaku Yamahata <isaku.yamahata@intel.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-10-01KVM: MMU: change FNAME(fetch)() arguments to kvm_page_faultPaolo Bonzini
Pass struct kvm_page_fault to FNAME(fetch)() instead of extracting the arguments from the struct. Suggested-by: Isaku Yamahata <isaku.yamahata@intel.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-10-01KVM: MMU: change __direct_map() arguments to kvm_page_faultPaolo Bonzini
Pass struct kvm_page_fault to __direct_map() instead of extracting the arguments from the struct. Suggested-by: Isaku Yamahata <isaku.yamahata@intel.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-10-01KVM: MMU: change handle_abnormal_pfn() arguments to kvm_page_faultPaolo Bonzini
Pass struct kvm_page_fault to handle_abnormal_pfn() instead of extracting the arguments from the struct. Suggested-by: Isaku Yamahata <isaku.yamahata@intel.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-10-01KVM: MMU: change kvm_faultin_pfn() arguments to kvm_page_faultPaolo Bonzini
Add fields to struct kvm_page_fault corresponding to outputs of kvm_faultin_pfn(). For now they have to be extracted again from struct kvm_page_fault in the subsequent steps, but this is temporary until other functions in the chain are switched over as well. Suggested-by: Isaku Yamahata <isaku.yamahata@intel.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-10-01KVM: MMU: change page_fault_handle_page_track() arguments to kvm_page_faultPaolo Bonzini
Add fields to struct kvm_page_fault corresponding to the arguments of page_fault_handle_page_track(). The fields are initialized in the callers, and page_fault_handle_page_track() receives a struct kvm_page_fault instead of having to extract the arguments out of it. Suggested-by: Isaku Yamahata <isaku.yamahata@intel.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-10-01KVM: MMU: change direct_page_fault() arguments to kvm_page_faultPaolo Bonzini
Add fields to struct kvm_page_fault corresponding to the arguments of direct_page_fault(). The fields are initialized in the callers, and direct_page_fault() receives a struct kvm_page_fault instead of having to extract the arguments out of it. Also adjust FNAME(page_fault) to store the max_level in struct kvm_page_fault, to keep it similar to the direct map path. Suggested-by: Isaku Yamahata <isaku.yamahata@intel.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-10-01KVM: MMU: change mmu->page_fault() arguments to kvm_page_faultPaolo Bonzini
Pass struct kvm_page_fault to mmu->page_fault() instead of extracting the arguments from the struct. FNAME(page_fault) can use the precomputed bools from the error code. Suggested-by: Isaku Yamahata <isaku.yamahata@intel.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-10-01KVM: MMU: Introduce struct kvm_page_faultPaolo Bonzini
Create a single structure for arguments that are passed from kvm_mmu_do_page_fault to the page fault handlers. Later the structure will grow to include various output parameters that are passed back to the next steps in the page fault handling. Suggested-by: Isaku Yamahata <isaku.yamahata@intel.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-10-01KVM: MMU: pass unadulterated gpa to direct_page_faultPaolo Bonzini
Do not bother removing the low bits of the gpa. This masking dates back to the very first commit of KVM but it is unnecessary, as exemplified by the other call in kvm_tdp_page_fault. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-10-01KVM: x86: Fix potential race in KVM_GET_CLOCKOliver Upton
Sean noticed that KVM_GET_CLOCK was checking kvm_arch.use_master_clock outside of the pvclock sync lock. This is problematic, as the clock value written to the user may or may not actually correspond to a stable TSC. Fix the race by populating the entire kvm_clock_data structure behind the pvclock_gtod_sync_lock. Suggested-by: Sean Christopherson <seanjc@google.com> Signed-off-by: Oliver Upton <oupton@google.com> Message-Id: <20210916181538.968978-4-oupton@google.com> Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-10-01KVM: x86: extract KVM_GET_CLOCK/KVM_SET_CLOCK to separate functionsPaolo Bonzini
No functional change intended. Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-10-01kvm: x86: abstract locking around pvclock_update_vm_gtod_copyPaolo Bonzini
Updates to the kvmclock parameters needs to do a complicated dance of KVM_REQ_MCLOCK_INPROGRESS and KVM_REQ_CLOCK_UPDATE in addition to taking pvclock_gtod_sync_lock. Place that in two functions that can be called on all of master clock update, KVM_SET_CLOCK, and Hyper-V reenlightenment. Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-10-01KVM: X86: Move PTE present check from loop body to __shadow_walk_next()Lai Jiangshan
So far, the loop bodies already ensure the PTE is present before calling __shadow_walk_next(): Some loop bodies simply exit with a !PRESENT directly and some other loop bodies, i.e. FNAME(fetch) and __direct_map() do not currently guard their walks with is_shadow_present_pte, but only because they install present non-leaf SPTEs in the loop itself. But checking pte present in __shadow_walk_next() (which is called from shadow_walk_okay()) is more prudent; walking past a !PRESENT SPTE would lead to attempting to read a the next level SPTE from a garbage iter->shadow_addr. It also allows to remove the is_shadow_present_pte() checks from the loop bodies. Reviewed-by: Sean Christopherson <seanjc@google.com> Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com> Message-Id: <20210906122547.263316-2-jiangshanlai@gmail.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-10-01KVM: x86: nSVM: implement nested TSC scalingMaxim Levitsky
This was tested by booting a nested guest with TSC=1Ghz, observing the clocks, and doing about 100 cycles of migration. Note that qemu patch is needed to support migration because of a new MSR that needs to be placed in the migration state. The patch will be sent to the qemu mailing list soon. Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com> Message-Id: <20210914154825.104886-14-mlevitsk@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-10-01KVM: x86: SVM: add module param to control TSC scalingMaxim Levitsky
This allows to easily simulate a CPU without this feature. Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com> Message-Id: <20210914154825.104886-13-mlevitsk@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-10-01KVM: x86: SVM: don't set VMLOAD/VMSAVE intercepts on vCPU resetPaolo Bonzini
Commit adc2a23734ac ("KVM: nSVM: improve SYSENTER emulation on AMD"), made init_vmcb set vmload/vmsave intercepts unconditionally, and relied on svm_vcpu_after_set_cpuid to clear them when possible. However init_vmcb is also called when the vCPU is reset, and it is not followed by another call to svm_vcpu_after_set_cpuid because the CPUID is already set. This mistake makes the VMSAVE/VMLOAD intercept to be set when it is not needed, and harms performance of the nested guest. Extract the relevant parts of svm_vcpu_after_set_cpuid so that they can be called again on reset. Fixes: adc2a23734ac ("KVM: nSVM: improve SYSENTER emulation on AMD") Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-09-30KVM: x86: SVM: add module param to control LBR virtualizationMaxim Levitsky
This is useful for debug and also makes it consistent with the rest of the SVM optional features. Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com> Message-Id: <20210914154825.104886-9-mlevitsk@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-09-30KVM: x86: nSVM: don't copy pause related settingsMaxim Levitsky
According to the SDM, the CPU never modifies these settings. It loads them on VM entry and updates an internal copy instead. Also don't load them from the vmcb12 as we don't expose these features to the nested guest yet. Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com> Message-Id: <20210914154825.104886-5-mlevitsk@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-09-30kvm: irqfd: avoid update unmodified entries of the routingLongpeng(Mike)
All of the irqfds would to be updated when update the irq routing, it's too expensive if there're too many irqfds. However we can reduce the cost by avoid some unnecessary updates. For irqs of MSI type on X86, the update can be saved if the msi values are not change. The vfio migration could receives benefit from this optimi- zaiton. The test VM has 128 vcpus and 8 VF (with 65 vectors enabled), so the VM has more than 520 irqfds. We mesure the cost of the vfio_msix_enable (in QEMU, it would set routing for each irqfd) for each VF, and we can see the total cost can be significantly reduced. Origin Apply this Patch 1st 8 4 2nd 15 5 3rd 22 6 4th 24 6 5th 36 7 6th 44 7 7th 51 8 8th 58 8 Total 258ms 51ms We're also tring to optimize the QEMU part [1], but it's still worth to optimize the KVM to gain more benefits. [1] https://lists.gnu.org/archive/html/qemu-devel/2021-08/msg04215.html Signed-off-by: Longpeng(Mike) <longpeng2@huawei.com> Message-Id: <20210827080003.2689-1-longpeng2@huawei.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-09-30KVM: X86: Don't check unsync if the original spte is writibleLai Jiangshan
If the original spte is writable, the target gfn should not be the gfn of synchronized shadowpage and can continue to be writable. When !can_unsync, speculative must be false. So when the check of "!can_unsync" is removed, we need to move the label of "out" up. Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Message-Id: <20210918005636.3675-11-jiangshanlai@gmail.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-09-30KVM: X86: Don't unsync pagetables when speculativeLai Jiangshan
We'd better only unsync the pagetable when there just was a really write fault on a level-1 pagetable. Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Message-Id: <20210918005636.3675-10-jiangshanlai@gmail.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-09-30KVM: X86: Remove FNAME(update_pte)Lai Jiangshan
Its solo caller is changed to use FNAME(prefetch_gpte) directly. Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Message-Id: <20210918005636.3675-9-jiangshanlai@gmail.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-09-30KVM: X86: Zap the invalid list after remote tlb flushingLai Jiangshan
In mmu_sync_children(), it can zap the invalid list after remote tlb flushing. Emptifying the invalid list ASAP might help reduce a remote tlb flushing in some cases. Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Message-Id: <20210918005636.3675-8-jiangshanlai@gmail.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-09-30KVM: X86: Change kvm_sync_page() to return true when remote flush is neededLai Jiangshan
Currently kvm_sync_page() returns true when there is any present spte. But the return value is ignored in the callers. Changing kvm_sync_page() to return true when remote flush is needed and changing mmu->sync_page() not to directly flush can combine and reduce remote flush requests. Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Message-Id: <20210918005636.3675-7-jiangshanlai@gmail.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-09-30KVM: X86: Remove kvm_mmu_flush_or_zap()Lai Jiangshan
Because local_flush is useless, kvm_mmu_flush_or_zap() can be removed and kvm_mmu_remote_flush_or_zap is used instead. Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Message-Id: <20210918005636.3675-6-jiangshanlai@gmail.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-09-30KVM: X86: Don't flush current tlb on shadow page modificationLai Jiangshan
After any shadow page modification, flushing tlb only on current VCPU is weird due to other VCPU's tlb might still be stale. In other words, if there is any mandatory tlb-flushing after shadow page modification, SET_SPTE_NEED_REMOTE_TLB_FLUSH or remote_flush should be set and the tlbs of all VCPUs should be flushed. There is not point to only flush current tlb except when the request is from vCPU's or pCPU's activities. If there was any bug that mandatory tlb-flushing is required and SET_SPTE_NEED_REMOTE_TLB_FLUSH/remote_flush is failed to set, this patch would expose the bug in a more destructive way. The related code paths are checked and no missing SET_SPTE_NEED_REMOTE_TLB_FLUSH is found yet. Currently, there is no optional tlb-flushing after sync page related code is changed to flush tlb timely. So we can just remove these local flushing code. Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Message-Id: <20210918005636.3675-5-jiangshanlai@gmail.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-09-30KVM: x86/mmu: Complete prefetch for trailing SPTEs for direct, legacy MMUSean Christopherson
Make a final call to direct_pte_prefetch_many() if there are "trailing" SPTEs to prefetch, i.e. SPTEs for GFNs following the faulting GFN. The call to direct_pte_prefetch_many() in the loop only handles the case where there are !PRESENT SPTEs preceding a PRESENT SPTE. E.g. if the faulting GFN is a multiple of 8 (the prefetch size) and all SPTEs for the following GFNs are !PRESENT, the loop will terminate with "start = sptep+1" and not prefetch any SPTEs. Prefetching trailing SPTEs as intended can drastically reduce the number of guest page faults, e.g. accessing the first byte of every 4kb page in a 6gb chunk of virtual memory, in a VM with 8gb of preallocated memory, the number of pf_fixed events observed in L0 drops from ~1.75M to <0.27M. Note, this only affects memory that is backed by 4kb pages as KVM doesn't prefetch when installing hugepages. Shadow paging prefetching is not affected as it does not batch the prefetches due to the need to process the corresponding guest PTE. The TDP MMU is not affected because it doesn't have prefetching, yet... Fixes: 957ed9effd80 ("KVM: MMU: prefetch ptes when intercepted guest #PF") Cc: Sergey Senozhatsky <senozhatsky@google.com> Cc: Ben Gardon <bgardon@google.com> Signed-off-by: Sean Christopherson <seanjc@google.com> Message-Id: <20210818235615.2047588-1-seanjc@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-09-30KVM: selftests: Fix kvm_vm_free() in cr4_cpuid_sync and vmx_tsc_adjust testsThomas Huth
The kvm_vm_free() statement here is currently dead code, since the loop in front of it can only be left with the "goto done" that jumps right after the kvm_vm_free(). Fix it by swapping the locations of the "done" label and the kvm_vm_free(). Signed-off-by: Thomas Huth <thuth@redhat.com> Message-Id: <20210826074928.240942-1-thuth@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-09-30kvm: selftests: Fix spelling mistake "missmatch" -> "mismatch"Colin Ian King
There is a spelling mistake in an error message. Fix it. Signed-off-by: Colin Ian King <colin.king@canonical.com> Message-Id: <20210826120752.12633-1-colin.king@canonical.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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