linux-kernel - Re: [PATCH v2 6/6] KVM: x86/mmu: Use 1 as the size of gfn range for tlb flushing in FNAME(invlpg)()

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Message-ID: <YxjXgERSNIk4ZaN+@google.com>
Date:   Wed, 7 Sep 2022 10:40:16 -0700
From:   David Matlack <dmatlack@...gle.com>
To:     Hou Wenlong <houwenlong.hwl@...group.com>
Cc:     kvm@...r.kernel.org, Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 6/6] KVM: x86/mmu: Use 1 as the size of gfn range for
 tlb flushing in FNAME(invlpg)()

On Wed, Aug 24, 2022 at 05:29:23PM +0800, Hou Wenlong wrote:
> Only SP with PG_LEVLE_4K level could be unsync, so the size of gfn range
> must be 1.
> 
> Signed-off-by: Hou Wenlong <houwenlong.hwl@...group.com>
> ---
>  arch/x86/kvm/mmu/paging_tmpl.h | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/mmu/paging_tmpl.h b/arch/x86/kvm/mmu/paging_tmpl.h
> index 04149c704d5b..486a3163b1e4 100644
> --- a/arch/x86/kvm/mmu/paging_tmpl.h
> +++ b/arch/x86/kvm/mmu/paging_tmpl.h
> @@ -937,7 +937,8 @@ static void FNAME(invlpg)(struct kvm_vcpu *vcpu, gva_t gva, hpa_t root_hpa)
>  
>  			mmu_page_zap_pte(vcpu->kvm, sp, sptep, NULL);
>  			if (is_shadow_present_pte(old_spte))
> -				kvm_flush_remote_tlbs_sptep(vcpu->kvm, sptep);
> +				kvm_flush_remote_tlbs_gfn(vcpu->kvm,
> +					kvm_mmu_page_get_gfn(sp, sptep - sp->spt), 1);

The third argument to kvm_flush_remote_tlbs_gfn() is the level, not the
number of pages. But that aside, I don't understand why this patch is
necessary. kvm_flush_remote_tlbs_sptep() should already do the right
thing.

>  
>  			if (!rmap_can_add(vcpu))
>  				break;
> -- 
> 2.31.1
>