[v2,0/5] Remove uses of struct page from x86 and arm64 MMU

Message

David Stevens June 25, 2021, 7:36 a.m. UTC

KVM supports mapping VM_IO and VM_PFNMAP memory into the guest by using
follow_pte in gfn_to_pfn. However, the resolved pfns may not have
assoicated struct pages, so they should not be passed to pfn_to_page.
This series removes such calls from the x86 and arm64 secondary MMU. To
do this, this series introduces gfn_to_pfn_page functions that parallel
the gfn_to_pfn functions. These functions take an extra out parameter
which  contains the page if the hva was resovled by gup. This allows the
caller to call put_page only when necessated by gup.

The gfn_to_pfn functions are depreciated. For now the functions remain
with identical behavior to before, but callers should be migrated to the
new gfn_to_pfn_page functions. I added new functions instead of simply
adding another parameter to the existing functions to make it easier to
track down users of the deprecated functions.

I have migrated the x86 and arm64 secondary MMUs to the new
gfn_to_pfn_page functions.

This addresses CVE-2021-22543 on x86 and arm64.

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 (4):
  KVM: mmu: introduce new gfn_to_pfn_page functions
  KVM: x86/mmu: use gfn_to_pfn_page
  KVM: arm64/mmu: use gfn_to_pfn_page
  KVM: mmu: remove over-aggressive warnings

Nicholas Piggin (1):
  KVM: do not allow mapping valid but non-refcounted pages

 arch/arm64/kvm/mmu.c            |  26 +++--
 arch/x86/kvm/mmu/mmu.c          |  50 ++++-----
 arch/x86/kvm/mmu/mmu_internal.h |   3 +-
 arch/x86/kvm/mmu/paging_tmpl.h  |  23 +++--
 arch/x86/kvm/mmu/tdp_mmu.c      |   6 +-
 arch/x86/kvm/mmu/tdp_mmu.h      |   4 +-
 arch/x86/kvm/x86.c              |   6 +-
 include/linux/kvm_host.h        |  17 +++
 virt/kvm/kvm_main.c             | 177 +++++++++++++++++++++++++-------
 9 files changed, 222 insertions(+), 90 deletions(-)