linux-kernel - Re: [PATCH] KVM: x86/mmu: Use yield-safe TDP MMU root iter in MMU notifier unmapping

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Date:   Sun, 21 Nov 2021 17:44:40 +0800
From:   Lai Jiangshan <jiangshanlai@...il.com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>,
        Hou Wenlong <houwenlong93@...ux.alibaba.com>
Subject: Re: [PATCH] KVM: x86/mmu: Use yield-safe TDP MMU root iter in MMU
 notifier unmapping

I guess it would conflict with c7785d85b6c6 ("KVM: x86/mmu:
Skip tlb flush if it has been done in zap_gfn_range()") from
Hou in the recent master branch in kvm tree.

On Sat, Nov 20, 2021 at 11:22 AM Sean Christopherson <seanjc@...gle.com> wrote:
>
> Use the yield-safe variant of the TDP MMU iterator when handling an
> unmapping event from the MMU notifier, as most occurences of the event
> allow yielding.

My spell check add-on in the browser tells:
 occurences ->  occurrences

>
> Fixes: e1eed5847b09 ("KVM: x86/mmu: Allow yielding during MMU notifier unmap/zap, if possible")
> Cc: stable@...r.kernel.org
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> ---
>  arch/x86/kvm/mmu/tdp_mmu.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
> index 377a96718a2e..a29ebff1cfa0 100644
> --- a/arch/x86/kvm/mmu/tdp_mmu.c
> +++ b/arch/x86/kvm/mmu/tdp_mmu.c
> @@ -1031,7 +1031,7 @@ 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)
> +       for_each_tdp_mmu_root_yield_safe(kvm, root, range->slot->as_id, false)
>                 flush |= zap_gfn_range(kvm, root, range->start, range->end,
>                                        range->may_block, flush, false);
>
> --
> 2.34.0.rc2.393.gf8c9666880-goog
>