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Date: Thu, 22 Apr 2021 17:06:35 -0700 From: Sean Christopherson <seanjc@...gle.com> To: Paolo Bonzini <pbonzini@...hat.com> Cc: 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>, kvm@...r.kernel.org, linux-kernel@...r.kernel.org Subject: [PATCH 2/4] KVM: nSVM: Drop pointless pdptrs_changed() check on nested transition Remove the "PDPTRs unchanged" check to skip PDPTR loading during nested SVM transitions as it's not at all an optimization. Reading guest memory to get the PDPTRs isn't magically cheaper by doing it in pdptrs_changed(), and if the PDPTRs did change, KVM will end up doing the read twice. Signed-off-by: Sean Christopherson <seanjc@...gle.com> --- arch/x86/kvm/svm/nested.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c index 540d43ba2cf4..9cc95895866a 100644 --- a/arch/x86/kvm/svm/nested.c +++ b/arch/x86/kvm/svm/nested.c @@ -391,10 +391,8 @@ static int nested_svm_load_cr3(struct kvm_vcpu *vcpu, unsigned long cr3, return -EINVAL; if (!nested_npt && is_pae_paging(vcpu) && - (cr3 != kvm_read_cr3(vcpu) || pdptrs_changed(vcpu))) { - if (CC(!load_pdptrs(vcpu, vcpu->arch.walk_mmu, cr3))) - return -EINVAL; - } + CC(!load_pdptrs(vcpu, vcpu->arch.walk_mmu, cr3))) + return -EINVAL; /* * TODO: optimize unconditional TLB flush/MMU sync here and in -- 2.31.1.498.g6c1eba8ee3d-goog
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