linux-kernel - Re: [GIT PULL] KVM: x86: MMU changes for 6.7

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Date:   Tue, 31 Oct 2023 15:20:41 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [GIT PULL] KVM: x86: MMU changes for 6.7

On Fri, Oct 27, 2023 at 10:49 PM Sean Christopherson <seanjc@...gle.com> wrote:
>
> This is mostly the first half of a series by Yan to optimize KVM's handling of
> guest MTRR changes for VMs with non-coherent DMA.  Yan had to put more complex
> changes that actually realize the optimizations on hold, but the patches here
> are all nice cleanups on their own.
>
> The following changes since commit 5804c19b80bf625c6a9925317f845e497434d6d3:
>
>   Merge tag 'kvm-riscv-fixes-6.6-1' of https://github.com/kvm-riscv/linux into HEAD (2023-09-23 05:35:55 -0400)

Pulled, thanks.

Paolo


> are available in the Git repository at:
>
>   https://github.com/kvm-x86/linux.git tags/kvm-x86-mmu-6.7
>
> for you to fetch changes up to 1de9992f9de0a92b6e11133aba0e2be833c11084:
>
>   KVM: x86/mmu: Remove unnecessary ‘NULL’ values from sptep (2023-10-18 14:34:28 -0700)
>
> ----------------------------------------------------------------
> KVM x86 MMU changes for 6.7:
>
>  - Clean up code that deals with honoring guest MTRRs when the VM has
>    non-coherent DMA and host MTRRs are ignored, i.e. EPT is enabled.
>
>  - Zap EPT entries when non-coherent DMA assignment stops/start to prevent
>    using stale entries with the wrong memtype.
>
>  - Don't ignore guest PAT for CR0.CD=1 && KVM_X86_QUIRK_CD_NW_CLEARED=y, as
>    there's zero reason to ignore guest PAT if the effective MTRR memtype is WB.
>    This will also allow for future optimizations of handling guest MTRR updates
>    for VMs with non-coherent DMA and the quirk enabled.
>
>  - Harden the fast page fault path to guard against encountering an invalid
>    root when walking SPTEs.
>
> ----------------------------------------------------------------
> Li zeming (1):
>       KVM: x86/mmu: Remove unnecessary ‘NULL’ values from sptep
>
> Yan Zhao (5):
>       KVM: x86/mmu: Add helpers to return if KVM honors guest MTRRs
>       KVM: x86/mmu: Zap SPTEs when CR0.CD is toggled iff guest MTRRs are honored
>       KVM: x86/mmu: Zap SPTEs on MTRR update iff guest MTRRs are honored
>       KVM: x86/mmu: Zap KVM TDP when noncoherent DMA assignment starts/stops
>       KVM: VMX: drop IPAT in memtype when CD=1 for KVM_X86_QUIRK_CD_NW_CLEARED
>
>  arch/x86/kvm/mmu.h     |  7 +++++++
>  arch/x86/kvm/mmu/mmu.c | 37 ++++++++++++++++++++++++++-----------
>  arch/x86/kvm/mtrr.c    |  2 +-
>  arch/x86/kvm/vmx/vmx.c |  9 +++------
>  arch/x86/kvm/x86.c     | 21 ++++++++++++++++++---
>  5 files changed, 55 insertions(+), 21 deletions(-)
>