On Mon, Jan 17, 2022 at 9:59 AM Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote:
>
> 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@xxxxxxxxxx/
> >
> > 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.
Thanks Paolo.
Patches 1 and 4 had some wordsmithing suggestions from Sean that I
think would be worth taking. I'm fine if you want to fold his
suggestions directly into the queued patches or I can resend.
The feedback on Patch 3 would require a follow-up series to address,
which I can handle separately.
>
> Paolo
>
