linux-kernel - Re: [PATCH v2 1/3] KVM: x86/mmu: Remove redundant spte present check in mmu_set

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Date:   Thu, 29 Jul 2021 18:16:52 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Mingwei Zhang <mizhang@...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,
        linux-kernel@...r.kernel.org, Ben Gardon <bgardon@...gle.com>,
        Jing Zhang <jingzhangos@...gle.com>
Subject: Re: [PATCH v2 1/3] KVM: x86/mmu: Remove redundant spte present check
 in mmu_set_spte

On Mon, Jul 26, 2021, 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@...gle.com>
> Signed-off-by: Mingwei Zhang <mizhang@...gle.com>
> ---

Reviewed-by: Sean Christopherson <seanjc@...gle.com>