Re: [PATCH v2 0/4] KVM: x86/mmu: Fix write-protection bug in the TDP MMU

[Paolo Bonzini <pbonzini@redhat.com>]

On 1/14/22 00:30, David Matlack wrote:
> While attempting to understand the big comment in
> kvm_mmu_slot_remove_write_access() about TLB flushing, I discovered a
> bug in the way the TDP MMU write-protects GFNs. I have not managed to
> reproduce the bug as it requires a rather complex set up of live
> migrating a VM that is using nested virtualization while the TDP MMU is
> enabled.
> 
> Patch 1 fixes the bug and is CC'd to stable.
> Patch 2-3 fix, document, and enforce invariants around MMU-writable
> and Host-writable bits.
> Patch 4 fixes up the aformentioned comment to be more readable.
> 
> Tested using the kvm-unit-tests and KVM selftests.
> 
> v2:
>   - Skip setting the SPTE when MMU-writable is already clear [Sean]
>   - Add patches for {MMU,Host}-writable invariants [Sean]
>   - Fix inaccuracies in kvm_mmu_slot_remove_write_access() comment [Sean]
> 
> v1: https://lore.kernel.org/kvm/20220112215801.3502286-1-dmatlack@google.com/
> 
> David Matlack (4):
>    KVM: x86/mmu: Fix write-protection of PTs mapped by the TDP MMU
>    KVM: x86/mmu: Clear MMU-writable during changed_pte notifier
>    KVM: x86/mmu: Document and enforce MMU-writable and Host-writable
>      invariants
>    KVM: x86/mmu: Improve TLB flush comment in
>      kvm_mmu_slot_remove_write_access()
> 
>   arch/x86/kvm/mmu/mmu.c     | 31 ++++++++++++++++++++--------
>   arch/x86/kvm/mmu/spte.c    |  1 +
>   arch/x86/kvm/mmu/spte.h    | 42 ++++++++++++++++++++++++++++++++------
>   arch/x86/kvm/mmu/tdp_mmu.c |  6 +++---
>   4 files changed, 62 insertions(+), 18 deletions(-)
> 
> 
> base-commit: fea31d1690945e6dd6c3e89ec5591490857bc3d4

Queued, thanks.

Paolo