linux-kernel - [PATCH 16/15] KVM: X86: Update mmu->pdptrs only when it is changed

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Date:   Thu, 11 Nov 2021 22:45:26 +0800
From:   Lai Jiangshan <jiangshanlai@...il.com>
To:     linux-kernel@...r.kernel.org
Cc:     kvm@...r.kernel.org, Lai Jiangshan <laijs@...ux.alibaba.com>,
        Paolo Bonzini <pbonzini@...hat.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: [PATCH 16/15] KVM: X86: Update mmu->pdptrs only when it is changed

From: Lai Jiangshan <laijs@...ux.alibaba.com>

It is unchanged in most cases.

Signed-off-by: Lai Jiangshan <laijs@...ux.alibaba.com>
---
 arch/x86/kvm/x86.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 6ca19cac4aff..0176eaa86a35 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -828,10 +828,13 @@ int load_pdptrs(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu, unsigned long cr3)
 		}
 	}
 
-	memcpy(mmu->pdptrs, pdpte, sizeof(mmu->pdptrs));
-	kvm_register_mark_dirty(vcpu, VCPU_EXREG_PDPTR);
-	/* Ensure the dirty PDPTEs to be loaded. */
-	kvm_make_request(KVM_REQ_LOAD_MMU_PGD, vcpu);
+	kvm_register_mark_available(vcpu, VCPU_EXREG_PDPTR);
+	if (memcmp(mmu->pdptrs, pdpte, sizeof(mmu->pdptrs))) {
+		memcpy(mmu->pdptrs, pdpte, sizeof(mmu->pdptrs));
+		kvm_register_mark_dirty(vcpu, VCPU_EXREG_PDPTR);
+		/* Ensure the dirty PDPTEs to be loaded. */
+		kvm_make_request(KVM_REQ_LOAD_MMU_PGD, vcpu);
+	}
 	vcpu->arch.pdptrs_from_userspace = false;
 
 	return 1;
-- 
2.19.1.6.gb485710b