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SubjectRe: [PATCH 09/12] KVM: MMU: coalesce zapping page after mmu_sync_children
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On 2016/02/24 22:17, Paolo Bonzini wrote:
> Move the call to kvm_mmu_flush_or_zap outside the loop.
>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
> arch/x86/kvm/mmu.c | 9 ++++++---
> 1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index 725316df32ec..6d47b5c43246 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -2029,24 +2029,27 @@ static void mmu_sync_children(struct kvm_vcpu *vcpu,
> struct mmu_page_path parents;
> struct kvm_mmu_pages pages;
> LIST_HEAD(invalid_list);
> + bool flush = false;
>
> while (mmu_unsync_walk(parent, &pages)) {
> bool protected = false;
> - bool flush = false;
>
> for_each_sp(pages, sp, parents, i)
> protected |= rmap_write_protect(vcpu, sp->gfn);
>
> - if (protected)
> + if (protected) {
> kvm_flush_remote_tlbs(vcpu->kvm);
> + flush = false;
> + }
>
> for_each_sp(pages, sp, parents, i) {
> flush |= kvm_sync_page(vcpu, sp, &invalid_list);
> mmu_pages_clear_parents(&parents);
> }
> - kvm_mmu_flush_or_zap(vcpu, &invalid_list, false, flush);
> cond_resched_lock(&vcpu->kvm->mmu_lock);

This may release the mmu_lock before committing the zapping.
Is it safe? If so, we may want to see the reason in the changelog.

Takuya

> }
> +
> + kvm_mmu_flush_or_zap(vcpu, &invalid_list, false, flush);
> }
>
> static void __clear_sp_write_flooding_count(struct kvm_mmu_page *sp)
>



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