KVM: SVM: implement enhanced INVLPG intercept

When the DecodeAssist feature is available, the linear address
is provided in the VMCB on INVLPG intercepts. Use it directly to
avoid any decoding and emulation.
This is only useful for shadow paging, though.
Signed-off-by: Andre Przywara <andre.przywara@amd.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

arch/x86/kvm/svm.c

@@ -2652,7 +2652,12 @@ static int iret_interception(struct vcpu_svm *svm)
 
 static int invlpg_interception(struct vcpu_svm *svm)
 {
-	return emulate_instruction(&svm->vcpu, 0) == EMULATE_DONE;
+	if (!static_cpu_has(X86_FEATURE_DECODEASSISTS))
+		return emulate_instruction(&svm->vcpu, 0) == EMULATE_DONE;
+
+	kvm_mmu_invlpg(&svm->vcpu, svm->vmcb->control.exit_info_1);
+	skip_emulated_instruction(&svm->vcpu);
+	return 1;
 }
 
 static int emulate_on_interception(struct vcpu_svm *svm)