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

[Lai Jiangshan]

From: Lai Jiangshan <laijs@xxxxxxxxxxxxxxxxx>

It is unchanged in most cases.

Signed-off-by: Lai Jiangshan <laijs@xxxxxxxxxxxxxxxxx>
---
 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