KVM: X86: Update mmu->pdptrs only when it is changed

Lai Jiangshan · bonzini · commit 24cd19a28cb7 · 2021-12-08T04:25:04.000-05:00
It is unchanged in most cases.

Signed-off-by: Lai Jiangshan &lt;laijs@linux.alibaba.com&gt;
Message-Id: &lt;20211111144527.88852-1-jiangshanlai@gmail.com&gt;
Signed-off-by: Paolo Bonzini &lt;pbonzini@redhat.com&gt;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
@@ -828,9 +828,12 @@ 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);
-	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);
+		kvm_make_request(KVM_REQ_LOAD_MMU_PGD, vcpu);
+	}
 	vcpu->arch.pdptrs_from_userspace = false;
 
 	return 1;

Original file line number	Diff line number	Diff line change
`@@ -828,9 +828,12 @@ int load_pdptrs(struct kvm_vcpu vcpu, struct kvm_mmu mmu, unsigned long cr3)`
`828`	`828`	`}`
`829`	`829`	`}`
`830`	`830`
`831`		`- memcpy(mmu->pdptrs, pdpte, sizeof(mmu->pdptrs));`
`832`		`- kvm_register_mark_dirty(vcpu, VCPU_EXREG_PDPTR);`
`833`		`- kvm_make_request(KVM_REQ_LOAD_MMU_PGD, vcpu);`
	`831`	`+ kvm_register_mark_available(vcpu, VCPU_EXREG_PDPTR);`
	`832`	`+ if (memcmp(mmu->pdptrs, pdpte, sizeof(mmu->pdptrs))) {`
	`833`	`+ memcpy(mmu->pdptrs, pdpte, sizeof(mmu->pdptrs));`
	`834`	`+ kvm_register_mark_dirty(vcpu, VCPU_EXREG_PDPTR);`
	`835`	`+ kvm_make_request(KVM_REQ_LOAD_MMU_PGD, vcpu);`
	`836`	`+ }`
`834`	`837`	`vcpu->arch.pdptrs_from_userspace = false;`
`835`	`838`
`836`	`839`	`return 1;`