| Message ID | 20230704075054.3344915-1-stevensd@google.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | KVM: allow mapping non-refcounted pages | expand |
On Tue, Jul 04, 2023, David Stevens wrote: > From: David Stevens <stevensd@chromium.org> > > This patch series adds support for mapping VM_IO and VM_PFNMAP memory > that is backed by struct pages that aren't currently being refcounted > (e.g. tail pages of non-compound higher order allocations) into the > guest. Aplogies for the slow review, I'm done with feedback for this version. FWIW, it's probably too bit late to catch 6.6, especially since we need acks from ARM and PPC, but 6.7 should be very doable unless someone outright objects. Thanks for being persistent!
From: David Stevens <stevensd@chromium.org> This patch series adds support for mapping VM_IO and VM_PFNMAP memory that is backed by struct pages that aren't currently being refcounted (e.g. tail pages of non-compound higher order allocations) into the guest. Our use case is virtio-gpu blob resources [1], which directly map host graphics buffers into the guest as "vram" for the virtio-gpu device. This feature currently does not work on systems using the amdgpu driver, as that driver allocates non-compound higher order pages via ttm_pool_alloc_page. First, this series replaces the __gfn_to_pfn_memslot API with a more extensible __kvm_faultin_pfn API. The updated API rearranges __gfn_to_pfn_memslot's args into a struct and where possible packs the bool arguments into a FOLL_ flags argument. The refactoring changes do not change any behavior, except as noted in the PPC change. When introduced in the refactoring, __kvm_faultin_pfn implies FOLL_GET to preserve existing behavior. From there, the API is made to support mapping non-refcounted pages by respecting the FOLL_GET flag. This series only adds support for non-refcounted pages to the x86 MMU. Other MMUs can likely be updated without too much difficulty, but it is not needed at this point. Updating other parts of KVM (e.g. pfncache) is not straightforward [2]. [1] https://patchwork.kernel.org/project/dri-devel/cover/20200814024000.2485-1-gurchetansingh@chromium.org/ [2] https://lore.kernel.org/all/ZBEEQtmtNPaEqU1i@google.com/ v6 -> v7: - Replace __gfn_to_pfn_memslot with a more flexible __kvm_faultin_pfn, and extend that API to support non-refcounted pages. v5 -> v6: - rebase on kvm next branch - rename gfn_to_pfn_page to gfn_to_pfn_noref - fix uninitialized outparam in error case of __kvm_faultin_pfn - add kvm_release_pfn_noref_clean for releasing pfn/page pair v4 -> v5: - rebase on kvm next branch again v3 -> v4: - rebase on kvm next branch again - Add some more context to a comment in ensure_pfn_ref v2 -> v3: - rebase on kvm next branch v1 -> v2: - Introduce new gfn_to_pfn_page functions instead of modifying the behavior of existing gfn_to_pfn functions, to make the change less invasive. - Drop changes to mmu_audit.c - Include Nicholas Piggin's patch to avoid corrupting refcount in the follow_pte case, and use it in depreciated gfn_to_pfn functions. - Rebase on kvm/next David Stevens (7): KVM: Introduce __kvm_follow_pfn function KVM: Make __kvm_follow_pfn not imply FOLL_GET KVM: x86/mmu: Migrate to __kvm_follow_pfn KVM: x86/mmu: Don't pass FOLL_GET to __kvm_follow_pfn KVM: arm64: Migrate to __kvm_follow_pfn KVM: PPC: Migrate to __kvm_follow_pfn KVM: remove __gfn_to_pfn_memslot Sean Christopherson (1): KVM: Assert that a page's refcount is elevated when marking accessed/dirty arch/arm64/kvm/mmu.c | 25 +-- arch/powerpc/include/asm/kvm_book3s.h | 2 +- arch/powerpc/kvm/book3s_64_mmu_hv.c | 38 ++--- arch/powerpc/kvm/book3s_64_mmu_radix.c | 50 +++--- arch/powerpc/kvm/book3s_hv_nested.c | 4 +- arch/x86/kvm/mmu/mmu.c | 77 ++++++--- arch/x86/kvm/mmu/mmu_internal.h | 1 + arch/x86/kvm/mmu/paging_tmpl.h | 9 +- arch/x86/kvm/mmu/spte.c | 4 +- arch/x86/kvm/mmu/spte.h | 12 +- arch/x86/kvm/mmu/tdp_mmu.c | 22 +-- include/linux/kvm_host.h | 26 +++ virt/kvm/kvm_main.c | 210 +++++++++++++------------ virt/kvm/kvm_mm.h | 3 +- virt/kvm/pfncache.c | 8 +- 15 files changed, 282 insertions(+), 209 deletions(-)