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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> |
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| .. | ||
| Kconfig | ||
| Makefile | ||
| virtio_balloon.c | ||
| virtio_input.c | ||
| virtio_mem.c | ||
| virtio_mmio.c | ||
| virtio_pci_common.c | ||
| virtio_pci_common.h | ||
| virtio_pci_legacy.c | ||
| virtio_pci_modern.c | ||
| virtio_ring.c | ||
| virtio_vdpa.c | ||
| virtio.c | ||