Re: [PATCH 1/2] KVM: x86/mmu: Skip tlb flush if it has been done in zap_gfn_range()

Sean Christopherson
2021-11-17T15:56:09Z

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
>