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bh=DkoqzghGXkp4JTswxtHKmjuCRqg+mzIS/snExybiSds=; b=GDAsqTGQ7YkUELCu5ewLbqoJ+pUT97DEpJec9O1ZkFke/ds2fTiZ/dXlhZpajn4+NZ scGNB1ypwN256l3lBumYeK/v0KQObm/TYK52iBQEdgK+VTRcAw6x3ou5UrAFmb4Zrop5 VGkmv2/Rtut1qHAz7p7+JTo04EbxaHTiNapmb/YdNdhya4NCQiJSr0J+q6w0RENWMe5I tS5or/rLfg0KN89GrXm3wW0nDt/4IGNisYEbS5v2vRzpOT1uiP66levcZhUcV3vCvvxz p0/sk893XijD0p3E7XsU1g8ET5CYS0gn6HyrDT8GKn1NJftWxTqZLKaALc1H9cFKB6gR Nuag== X-Gm-Message-State: AOAM531krQXkjjl1MrwYhne+IDWf+NcCRuRWahaMzTo/8i8xP84fkdoN woOfrZ/J3sDoVhmP1/jnNU4nimY+hqqOWnQP7EB4Vg== X-Google-Smtp-Source: ABdhPJwVZJ2nWBQp3UnRp9rETNq+3gaocT9GC6cbYNfkUE5vuLPdR9MQ6f4zr4kP2b4NydwDOZe5x3ndV51OWSmfodg= X-Received: by 2002:a02:cab9:: with SMTP id e25mr17930118jap.25.1627331025078; Mon, 26 Jul 2021 13:23:45 -0700 (PDT) MIME-Version: 1.0 References: <20210726175357.1572951-1-mizhang@google.com> <20210726175357.1572951-2-mizhang@google.com> In-Reply-To: <20210726175357.1572951-2-mizhang@google.com> From: Ben Gardon Date: Mon, 26 Jul 2021 13:23:34 -0700 Message-ID: Subject: Re: [PATCH v2 1/3] KVM: x86/mmu: Remove redundant spte present check in mmu_set_spte To: Mingwei Zhang Cc: Paolo Bonzini , Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , kvm , LKML , Jing Zhang Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jul 26, 2021 at 10:54 AM 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 > Signed-off-by: Mingwei Zhang Reviewed-by: Ben Gardon > --- > 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; > -- > 2.32.0.432.gabb21c7263-goog >