KVM: Cache pdptrs

Instead of reloading the pdptrs on every entry and exit (vmcs writes on vmx,
guest memory access on svm) extract them on demand.

Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 75e9df0..2ad8c97 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -246,6 +246,10 @@
 	ret = 1;
 
 	memcpy(vcpu->arch.pdptrs, pdpte, sizeof(vcpu->arch.pdptrs));
+	__set_bit(VCPU_EXREG_PDPTR,
+		  (unsigned long *)&vcpu->arch.regs_avail);
+	__set_bit(VCPU_EXREG_PDPTR,
+		  (unsigned long *)&vcpu->arch.regs_dirty);
 out:
 
 	return ret;
@@ -261,6 +265,10 @@
 	if (is_long_mode(vcpu) || !is_pae(vcpu))
 		return false;
 
+	if (!test_bit(VCPU_EXREG_PDPTR,
+		      (unsigned long *)&vcpu->arch.regs_avail))
+		return true;
+
 	r = kvm_read_guest(vcpu->kvm, vcpu->arch.cr3 & ~31u, pdpte, sizeof(pdpte));
 	if (r < 0)
 		goto out;