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    SubjectRe: [PATCH 1/2] KVM: x86/mmu: Skip tlb flush if it has been done in zap_gfn_range()
    On Wed, Nov 17, 2021, Hou Wenlong wrote:
    > If the parameter flush is set, zap_gfn_range() would flush remote tlb
    > when yield, then tlb flush is not needed outside. So use the return
    > value of zap_gfn_range() directly instead of OR on it in
    > kvm_unmap_gfn_range() and kvm_tdp_mmu_unmap_gfn_range().
    >
    > Fixes: 3039bcc744980 ("KVM: Move x86's MMU notifier memslot walkers to generic code")
    > Signed-off-by: Hou Wenlong <houwenlong93@linux.alibaba.com>
    > ---

    Ha, I fixed this in my local repo just yesterday :-)

    Reviewed-by: Sean Christopherson <seanjc@google.com>

    > arch/x86/kvm/mmu/mmu.c | 2 +-
    > arch/x86/kvm/mmu/tdp_mmu.c | 4 ++--
    > 2 files changed, 3 insertions(+), 3 deletions(-)
    >
    > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
    > index 354d2ca92df4..d57319e596a9 100644
    > --- a/arch/x86/kvm/mmu/mmu.c
    > +++ b/arch/x86/kvm/mmu/mmu.c
    > @@ -1582,7 +1582,7 @@ bool kvm_unmap_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range)
    > flush = kvm_handle_gfn_range(kvm, range, kvm_unmap_rmapp);
    >
    > if (is_tdp_mmu_enabled(kvm))
    > - flush |= kvm_tdp_mmu_unmap_gfn_range(kvm, range, flush);
    > + flush = kvm_tdp_mmu_unmap_gfn_range(kvm, range, flush);
    >
    > return flush;
    > }
    > diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
    > index 7c5dd83e52de..9d03f5b127dc 100644
    > --- a/arch/x86/kvm/mmu/tdp_mmu.c
    > +++ b/arch/x86/kvm/mmu/tdp_mmu.c
    > @@ -1034,8 +1034,8 @@ bool kvm_tdp_mmu_unmap_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range,
    > struct kvm_mmu_page *root;
    >
    > for_each_tdp_mmu_root(kvm, root, range->slot->as_id)

    Another issue is that this should be for_each_tdp_mmu_root_yield_safe(). I'll get
    a patch out for that later today.

    > - flush |= zap_gfn_range(kvm, root, range->start, range->end,
    > - range->may_block, flush, false);
    > + flush = zap_gfn_range(kvm, root, range->start, range->end,
    > + range->may_block, flush, false);
    >
    > return flush;
    > }
    > --
    > 2.31.1
    >

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