kvm: nVMX: Add support for fast unprotection of nested guest page tables

This is the same as commit 147277540bbc ("kvm: svm: Add support for
additional SVM NPF error codes", 2016-11-23), but for Intel processors.
In this case, the exit qualification field's bit 8 says whether the
EPT violation occurred while translating the guest's final physical
address or rather while translating the guest page tables.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index c7cf5b1..ed1074e 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -6358,7 +6358,7 @@ static int handle_ept_violation(struct kvm_vcpu *vcpu)
 {
 	unsigned long exit_qualification;
 	gpa_t gpa;
-	u32 error_code;
+	u64 error_code;
 
 	exit_qualification = vmcs_readl(EXIT_QUALIFICATION);
 
@@ -6390,6 +6390,9 @@ static int handle_ept_violation(struct kvm_vcpu *vcpu)
 			EPT_VIOLATION_EXECUTABLE))
 		      ? PFERR_PRESENT_MASK : 0;
 
+	error_code |= (exit_qualification & 0x100) != 0 ?
+	       PFERR_GUEST_FINAL_MASK : PFERR_GUEST_PAGE_MASK;
+
 	vcpu->arch.gpa_available = true;
 	vcpu->arch.exit_qualification = exit_qualification;