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path: root/drivers/virtio/virtio_mem.c
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2020-06-04virtio-mem: Allow to offline partially unplugged memory blocksDavid Hildenbrand
Dropping the reference count of PageOffline() pages during MEM_GOING_ONLINE allows offlining code to skip them. However, we also have to clear PG_reserved, because PG_reserved pages get detected as unmovable right away. Take care of restoring the reference count when offlining is canceled. Clarify why we don't have to perform any action when unloading the driver. Also, let's add a warning if anybody is still holding a reference to unplugged pages when offlining. Tested-by: Pankaj Gupta <pankaj.gupta.linux@gmail.com> Cc: "Michael S. Tsirkin" <mst@redhat.com> Cc: Jason Wang <jasowang@redhat.com> Cc: Oscar Salvador <osalvador@suse.de> Cc: Michal Hocko <mhocko@kernel.org> Cc: Igor Mammedov <imammedo@redhat.com> Cc: Dave Young <dyoung@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Pavel Tatashin <pasha.tatashin@soleen.com> Cc: Stefan Hajnoczi <stefanha@redhat.com> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: David Hildenbrand <david@redhat.com> Link: https://lore.kernel.org/r/20200507140139.17083-8-david@redhat.com Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2020-06-04virtio-mem: Paravirtualized memory hotunplug part 2David Hildenbrand
We also want to unplug online memory (contained in online memory blocks and, therefore, managed by the buddy), and eventually replug it later. When requested to unplug memory, we use alloc_contig_range() to allocate subblocks in online memory blocks (so we are the owner) and send them to our hypervisor. When requested to plug memory, we can replug such memory using free_contig_range() after asking our hypervisor. We also want to mark all allocated pages PG_offline, so nobody will touch them. To differentiate pages that were never onlined when onlining the memory block from pages allocated via alloc_contig_range(), we use PageDirty(). Based on this flag, virtio_mem_fake_online() can either online the pages for the first time or use free_contig_range(). It is worth noting that there are no guarantees on how much memory can actually get unplugged again. All device memory might completely be fragmented with unmovable data, such that no subblock can get unplugged. We are not touching the ZONE_MOVABLE. If memory is onlined to the ZONE_MOVABLE, it can only get unplugged after that memory was offlined manually by user space. In normal operation, virtio-mem memory is suggested to be onlined to ZONE_NORMAL. In the future, we will try to make unplug more likely to succeed. Add a module parameter to control if online memory shall be touched. As we want to access alloc_contig_range()/free_contig_range() from kernel module context, export the symbols. Note: Whenever virtio-mem uses alloc_contig_range(), all affected pages are on the same node, in the same zone, and contain no holes. Acked-by: Michal Hocko <mhocko@suse.com> # to export contig range allocator API Tested-by: Pankaj Gupta <pankaj.gupta.linux@gmail.com> Cc: "Michael S. Tsirkin" <mst@redhat.com> Cc: Jason Wang <jasowang@redhat.com> Cc: Oscar Salvador <osalvador@suse.de> Cc: Michal Hocko <mhocko@kernel.org> Cc: Igor Mammedov <imammedo@redhat.com> Cc: Dave Young <dyoung@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Pavel Tatashin <pasha.tatashin@soleen.com> Cc: Stefan Hajnoczi <stefanha@redhat.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Mel Gorman <mgorman@techsingularity.net> Cc: Mike Rapoport <rppt@linux.ibm.com> Cc: Alexander Duyck <alexander.h.duyck@linux.intel.com> Cc: Alexander Potapenko <glider@google.com> Signed-off-by: David Hildenbrand <david@redhat.com> Link: https://lore.kernel.org/r/20200507140139.17083-6-david@redhat.com Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2020-06-04virtio-mem: Paravirtualized memory hotunplug part 1David Hildenbrand
Unplugging subblocks of memory blocks that are offline is easy. All we have to do is watch out for concurrent onlining activity. Tested-by: Pankaj Gupta <pankaj.gupta.linux@gmail.com> Cc: "Michael S. Tsirkin" <mst@redhat.com> Cc: Jason Wang <jasowang@redhat.com> Cc: Oscar Salvador <osalvador@suse.de> Cc: Michal Hocko <mhocko@kernel.org> Cc: Igor Mammedov <imammedo@redhat.com> Cc: Dave Young <dyoung@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Pavel Tatashin <pasha.tatashin@soleen.com> Cc: Stefan Hajnoczi <stefanha@redhat.com> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: David Hildenbrand <david@redhat.com> Link: https://lore.kernel.org/r/20200507140139.17083-5-david@redhat.com Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2020-06-04virtio-mem: Allow to specify an ACPI PXM as nidDavid Hildenbrand
We want to allow to specify (similar as for a DIMM), to which node a virtio-mem device (and, therefore, its memory) belongs. Add a new virtio-mem feature flag and export pxm_to_node, so it can be used in kernel module context. Acked-by: Michal Hocko <mhocko@suse.com> # for the export Acked-by: "Rafael J. Wysocki" <rafael@kernel.org> # for the export Acked-by: Pankaj Gupta <pankaj.gupta.linux@gmail.com> Tested-by: Pankaj Gupta <pankaj.gupta.linux@gmail.com> Cc: "Michael S. Tsirkin" <mst@redhat.com> Cc: Jason Wang <jasowang@redhat.com> Cc: Oscar Salvador <osalvador@suse.de> Cc: Michal Hocko <mhocko@kernel.org> Cc: Igor Mammedov <imammedo@redhat.com> Cc: Dave Young <dyoung@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Pavel Tatashin <pasha.tatashin@soleen.com> Cc: Stefan Hajnoczi <stefanha@redhat.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Len Brown <lenb@kernel.org> Cc: linux-acpi@vger.kernel.org Signed-off-by: David Hildenbrand <david@redhat.com> Link: https://lore.kernel.org/r/20200507140139.17083-4-david@redhat.com Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
2020-06-04virtio-mem: Paravirtualized memory hotplugDavid Hildenbrand
Each virtio-mem device owns exactly one memory region. It is responsible for adding/removing memory from that memory region on request. When the device driver starts up, the requested amount of memory is queried and then plugged to Linux. On request, further memory can be plugged or unplugged. This patch only implements the plugging part. On x86-64, memory can currently be plugged in 4MB ("subblock") granularity. When required, a new memory block will be added (e.g., usually 128MB on x86-64) in order to plug more subblocks. Only x86-64 was tested for now. The online_page callback is used to keep unplugged subblocks offline when onlining memory - similar to the Hyper-V balloon driver. Unplugged pages are marked PG_offline, to tell dump tools (e.g., makedumpfile) to skip them. User space is usually responsible for onlining the added memory. The memory hotplug notifier is used to synchronize virtio-mem activity against memory onlining/offlining. Each virtio-mem device can belong to a NUMA node, which allows us to easily add/remove small chunks of memory to/from a specific NUMA node by using multiple virtio-mem devices. Something that works even when the guest has no idea about the NUMA topology. One way to view virtio-mem is as a "resizable DIMM" or a DIMM with many "sub-DIMMS". This patch directly introduces the basic infrastructure to implement memory unplug. Especially the memory block states and subblock bitmaps will be heavily used there. Notes: - In case memory is to be onlined by user space, we limit the amount of offline memory blocks, to not run out of memory. This is esp. an issue if memory is added faster than it is getting onlined. - Suspend/Hibernate is not supported due to the way virtio-mem devices behave. Limited support might be possible in the future. - Reloading the device driver is not supported. Reviewed-by: Pankaj Gupta <pankaj.gupta.linux@gmail.com> Tested-by: Pankaj Gupta <pankaj.gupta.linux@gmail.com> Cc: "Michael S. Tsirkin" <mst@redhat.com> Cc: Jason Wang <jasowang@redhat.com> Cc: Oscar Salvador <osalvador@suse.de> Cc: Michal Hocko <mhocko@kernel.org> Cc: Igor Mammedov <imammedo@redhat.com> Cc: Dave Young <dyoung@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Pavel Tatashin <pasha.tatashin@soleen.com> Cc: Stefan Hajnoczi <stefanha@redhat.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net> Cc: Len Brown <lenb@kernel.org> Cc: linux-acpi@vger.kernel.org Signed-off-by: David Hildenbrand <david@redhat.com> Link: https://lore.kernel.org/r/20200507140139.17083-2-david@redhat.com Signed-off-by: Michael S. Tsirkin <mst@redhat.com>