linux-kernel - Re: [PATCH 00/18] KVM: x86/mmu: A/D cleanups (on top of kvm_follow

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Message-ID: <1012877d-1a99-4d0c-92bc-53025dfaf489@redhat.com>
Date: Thu, 17 Oct 2024 18:55:52 +0200
From: Paolo Bonzini <pbonzini@...hat.com>
To: Sean Christopherson <seanjc@...gle.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
 Yan Zhao <yan.y.zhao@...el.com>, Sagi Shahar <sagis@...gle.com>,
 Alex Bennée <alex.bennee@...aro.org>,
 David Matlack <dmatlack@...gle.com>, James Houghton <jthoughton@...gle.com>
Subject: Re: [PATCH 00/18] KVM: x86/mmu: A/D cleanups (on top of
 kvm_follow_pfn)

On 10/11/24 04:10, Sean Christopherson wrote:
> This is effectively an extensive of the kvm_follow_pfn series[*] (and
> applies on top of said series), but is x86-specific and is *almost*
> entirely related to Accessed and Dirty bits.
> 
> There's no central theme beyond cleaning up things that were discovered
> when digging deep for the kvm_follow_pfn overhaul, and to a lesser extent
> the series to add MGLRU support in KVM x86.

Very nice - looks obvious in retrospect, as it often happens.

Paolo

> [*] https://lore.kernel.org/all/20241010182427.1434605-1-seanjc@google.com
> 
> Sean Christopherson (18):
>    KVM: x86/mmu: Flush remote TLBs iff MMU-writable flag is cleared from
>      RO SPTE
>    KVM: x86/mmu: Always set SPTE's dirty bit if it's created as writable
>    KVM: x86/mmu: Fold all of make_spte()'s writable handling into one
>      if-else
>    KVM: x86/mmu: Don't force flush if SPTE update clears Accessed bit
>    KVM: x86/mmu: Don't flush TLBs when clearing Dirty bit in shadow MMU
>    KVM: x86/mmu: Drop ignored return value from
>      kvm_tdp_mmu_clear_dirty_slot()
>    KVM: x86/mmu: Fold mmu_spte_update_no_track() into mmu_spte_update()
>    KVM: x86/mmu: WARN and flush if resolving a TDP MMU fault clears
>      MMU-writable
>    KVM: x86/mmu: Add a dedicated flag to track if A/D bits are globally
>      enabled
>    KVM: x86/mmu: Set shadow_accessed_mask for EPT even if A/D bits
>      disabled
>    KVM: x86/mmu: Set shadow_dirty_mask for EPT even if A/D bits disabled
>    KVM: x86/mmu: Use Accessed bit even when _hardware_ A/D bits are
>      disabled
>    KVM: x86/mmu: Process only valid TDP MMU roots when aging a gfn range
>    KVM: x86/mmu: Stop processing TDP MMU roots for test_age if young SPTE
>      found
>    KVM: x86/mmu: Dedup logic for detecting TLB flushes on leaf SPTE
>      changes
>    KVM: x86/mmu: Set Dirty bit for new SPTEs, even if _hardware_ A/D bits
>      are disabled
>    KVM: Allow arch code to elide TLB flushes when aging a young page
>    KVM: x86: Don't emit TLB flushes when aging SPTEs for mmu_notifiers
> 
>   arch/x86/kvm/Kconfig       |   1 +
>   arch/x86/kvm/mmu/mmu.c     |  72 +++++++-----------------
>   arch/x86/kvm/mmu/spte.c    |  59 ++++++++------------
>   arch/x86/kvm/mmu/spte.h    |  72 ++++++++++++------------
>   arch/x86/kvm/mmu/tdp_mmu.c | 109 +++++++++++++++++--------------------
>   arch/x86/kvm/mmu/tdp_mmu.h |   2 +-
>   virt/kvm/Kconfig           |   4 ++
>   virt/kvm/kvm_main.c        |  20 ++-----
>   8 files changed, 142 insertions(+), 197 deletions(-)
> 
> 
> base-commit: 3f9cf3d569fdf7fb451294b636991291965573ce