linux-kernel - Re: [PATCH 2/2] KVM: X86: Don't reset mmu context when toggling X86_CR4

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Message-ID: <YWh8EndpDdHYX7aY@google.com>
Date:   Thu, 14 Oct 2021 18:50:58 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Lai Jiangshan <jiangshanlai@...il.com>
Cc:     linux-kernel@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>, kvm@...r.kernel.org,
        Lai Jiangshan <laijs@...ux.alibaba.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH 2/2] KVM: X86: Don't reset mmu context when toggling
 X86_CR4_PGE

On Sun, Sep 19, 2021, Lai Jiangshan wrote:
> From: Lai Jiangshan <laijs@...ux.alibaba.com>
> 
> X86_CR4_PGE doesn't participate in kvm_mmu_role, so the mmu context
> doesn't need to be reset.  It is only required to flush all the guest
> tlb.
> 
> It is also inconsistent that X86_CR4_PGE is in KVM_MMU_CR4_ROLE_BITS
> while kvm_mmu_role doesn't use X86_CR4_PGE.  So X86_CR4_PGE is also
> removed from KVM_MMU_CR4_ROLE_BITS.
> 
> Signed-off-by: Lai Jiangshan <laijs@...ux.alibaba.com>
> ---

With the KVM_REQ_TLB_FLUSH_GUEST caveat, 

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