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From: David Matlack <dmatlack@google.com>
To: Mingwei Zhang <mizhang@google.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
	Sean Christopherson <seanjc@google.com>,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	Wanpeng Li <wanpengli@tencent.com>,
	Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
	kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
	Ben Gardon <bgardon@google.com>,
	Jing Zhang <jingzhangos@google.com>
Subject: Re: [PATCH v3 1/3] KVM: x86/mmu: Remove redundant spte present check in mmu_set_spte
Date: Mon, 2 Aug 2021 22:29:19 +0000	[thread overview]
Message-ID: <YQhxv3XO931lk7ny@google.com> (raw)
In-Reply-To: <20210730225939.3852712-2-mizhang@google.com>

On Fri, Jul 30, 2021 at 03:59:37PM -0700, Mingwei Zhang wrote:
> Drop an unnecessary is_shadow_present_pte() check when updating the rmaps
> after installing a non-MMIO SPTE.  set_spte() is used only to create
> shadow-present SPTEs, e.g. MMIO SPTEs are handled early on, mmu_set_spte()
> runs with mmu_lock held for write, i.e. the SPTE can't be zapped between
> writing the SPTE and updating the rmaps.
> 
> Opportunistically combine the "new SPTE" logic for large pages and rmaps.
> 
> No functional change intended.
> 
> Suggested-by: Ben Gardon <bgardon@google.com>
> 
> Reviewed-by: Ben Gardon <bgardon@google.com>
> Reviewed-by: Sean Christopherson <seanjc@google.com>
> Signed-off-by: Mingwei Zhang <mizhang@google.com>
> ---

Reviewed-by: David Matlack <dmatlack@google.com>

>  arch/x86/kvm/mmu/mmu.c | 14 ++++++--------
>  1 file changed, 6 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index b888385d1933..442cc554ebd6 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -2690,15 +2690,13 @@ static int mmu_set_spte(struct kvm_vcpu *vcpu, u64 *sptep,
>  
>  	pgprintk("%s: setting spte %llx\n", __func__, *sptep);
>  	trace_kvm_mmu_set_spte(level, gfn, sptep);
> -	if (!was_rmapped && is_large_pte(*sptep))
> -		++vcpu->kvm->stat.lpages;
>  
> -	if (is_shadow_present_pte(*sptep)) {
> -		if (!was_rmapped) {
> -			rmap_count = rmap_add(vcpu, sptep, gfn);
> -			if (rmap_count > RMAP_RECYCLE_THRESHOLD)
> -				rmap_recycle(vcpu, sptep, gfn);
> -		}
> +	if (!was_rmapped) {
> +		if (is_large_pte(*sptep))
> +			++vcpu->kvm->stat.lpages;
> +		rmap_count = rmap_add(vcpu, sptep, gfn);
> +		if (rmap_count > RMAP_RECYCLE_THRESHOLD)
> +			rmap_recycle(vcpu, sptep, gfn);
>  	}
>  
>  	return ret;
> -- 
> 2.32.0.554.ge1b32706d8-goog
> 

  reply	other threads:[~2021-08-02 22:29 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-30 22:59 [PATCH v3 0/3] Add detailed page size stats in KVM stats Mingwei Zhang
2021-07-30 22:59 ` [PATCH v3 1/3] KVM: x86/mmu: Remove redundant spte present check in mmu_set_spte Mingwei Zhang
2021-08-02 22:29   ` David Matlack [this message]
2021-07-30 22:59 ` [PATCH v3 2/3] KVM: x86/mmu: Avoid collision with !PRESENT SPTEs in TDP MMU lpage stats Mingwei Zhang
2021-08-02 22:40   ` David Matlack
2021-07-30 22:59 ` [PATCH v3 3/3] KVM: x86/mmu: Add detailed page size stats Mingwei Zhang
2021-08-02 22:41   ` David Matlack
2021-08-02 23:02   ` Sean Christopherson
2021-08-02 23:45     ` Mingwei Zhang

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