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Message-ID: <bf732349-b7b3-ff4e-d6a4-b9755d26e378@redhat.com>
Date: Thu, 18 Nov 2021 16:17:56 +0100
From: Paolo Bonzini <pbonzini@...hat.com>
To: Lai Jiangshan <jiangshanlai@...il.com>,
linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc: Lai Jiangshan <laijs@...ux.alibaba.com>,
Sean Christopherson <seanjc@...gle.com>,
Vitaly Kuznetsov <vkuznets@...hat.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 09/15] KVM: SVM: Remove the unneeded code to mark
available for CR3
On 11/8/21 13:44, Lai Jiangshan wrote:
> From: Lai Jiangshan <laijs@...ux.alibaba.com>
>
> VCPU_EXREG_CR3 is never cleared from vcpu->arch.regs_avail in SVM so
> marking available for CR3 is mere an NOP, just remove it.
>
> And it is not required to mark it dirty since VCPU_EXREG_CR3 is neither
> never cleared from vcpu->arch.regs_dirty and SVM doesn't use the dirty
> information of VCPU_EXREG_CR3.
>
> Signed-off-by: Lai Jiangshan <laijs@...ux.alibaba.com>
> ---
> arch/x86/kvm/svm/nested.c | 1 -
> 1 file changed, 1 deletion(-)
>
> diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
> index 13a58722e097..2d88ff584d61 100644
> --- a/arch/x86/kvm/svm/nested.c
> +++ b/arch/x86/kvm/svm/nested.c
> @@ -444,7 +444,6 @@ static int nested_svm_load_cr3(struct kvm_vcpu *vcpu, unsigned long cr3,
> kvm_mmu_new_pgd(vcpu, cr3);
>
> vcpu->arch.cr3 = cr3;
> - kvm_register_mark_available(vcpu, VCPU_EXREG_CR3);
>
> /* Re-initialize the MMU, e.g. to pick up CR4 MMU role changes. */
> kvm_init_mmu(vcpu);
>
These two patches can be merged, I think, with a commit message like
VCPU_EXREG_CR3 is never cleared from vcpu->arch.regs_avail or
vcpu->arch.regs_dirty in SVM; therefore, marking CR3 as available is
merely a NOP, and testing it will likewise always succeed.
Paolo
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