linux-kernel - [PATCH v2 06/10] KVM: VMX: Don't invalidate hv_tlb

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Message-Id: <20201020215613.8972-7-sean.j.christopherson@intel.com>
Date:   Tue, 20 Oct 2020 14:56:09 -0700
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <sean.j.christopherson@...el.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 v2 06/10] KVM: VMX: Don't invalidate hv_tlb_eptp if the new EPTP matches

Don't invalidate the common EPTP, and thus trigger rechecking of EPTPs
across all vCPUs, if the new EPTP matches the old/common EPTP.  In all
likelihood this is a meaningless optimization, but there are (uncommon)
scenarios where KVM can reload the same EPTP.

Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
---
 arch/x86/kvm/vmx/vmx.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 4dfde8b64750..e6569bafacdc 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -3043,7 +3043,8 @@ static void vmx_load_mmu_pgd(struct kvm_vcpu *vcpu, unsigned long pgd,
 		if (kvm_x86_ops.tlb_remote_flush) {
 			spin_lock(&to_kvm_vmx(kvm)->ept_pointer_lock);
 			to_vmx(vcpu)->ept_pointer = eptp;
-			to_kvm_vmx(kvm)->hv_tlb_eptp = INVALID_PAGE;
+			if (eptp != to_kvm_vmx(kvm)->hv_tlb_eptp)
+				to_kvm_vmx(kvm)->hv_tlb_eptp = INVALID_PAGE;
 			spin_unlock(&to_kvm_vmx(kvm)->ept_pointer_lock);
 		}
 
-- 
2.28.0