x86: Delay skip of emulated hypercall instruction

The IP increment should be done after the hypercall emulation, after
calling the various handlers. In this way, these handlers can accurately
identify the the IP of the VMCALL if they need it.

This patch keeps the same functionality for the Hyper-V handler which does
not use the return code of the standard kvm_skip_emulated_instruction()
call.

Signed-off-by: Marian Rotariu <mrotariu@bitdefender.com>
[Hyper-V hypercalls also need kvm_skip_emulated_instruction() - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/hyperv.c

@@ -1265,7 +1265,7 @@ static int kvm_hv_hypercall_complete_userspace(struct kvm_vcpu *vcpu)
 	struct kvm_run *run = vcpu->run;
 
 	kvm_hv_hypercall_set_result(vcpu, run->hyperv.u.hcall.result);
-	return 1;
+	return kvm_skip_emulated_instruction(vcpu);
 }
 
 static u16 kvm_hvcall_signal_event(struct kvm_vcpu *vcpu, bool fast, u64 param)

arch/x86/kvm/x86.c

@@ -6671,12 +6671,13 @@ void kvm_vcpu_deactivate_apicv(struct kvm_vcpu *vcpu)
 int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
 {
 	unsigned long nr, a0, a1, a2, a3, ret;
-	int op_64_bit, r;
+	int op_64_bit;
 
-	r = kvm_skip_emulated_instruction(vcpu);
-
-	if (kvm_hv_hypercall_enabled(vcpu->kvm))
-		return kvm_hv_hypercall(vcpu);
+	if (kvm_hv_hypercall_enabled(vcpu->kvm)) {
+		if (!kvm_hv_hypercall(vcpu))
+			return 0;
+		goto out;
+	}
 
 	nr = kvm_register_read(vcpu, VCPU_REGS_RAX);
 	a0 = kvm_register_read(vcpu, VCPU_REGS_RBX);
@@ -6697,7 +6698,7 @@ int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
 
 	if (kvm_x86_ops->get_cpl(vcpu) != 0) {
 		ret = -KVM_EPERM;
-		goto out;
+		goto out_error;
 	}
 
 	switch (nr) {
@@ -6717,12 +6718,14 @@ int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
 		ret = -KVM_ENOSYS;
 		break;
 	}
-out:
+out_error:
 	if (!op_64_bit)
 		ret = (u32)ret;
 	kvm_register_write(vcpu, VCPU_REGS_RAX, ret);
+
+out:
 	++vcpu->stat.hypercalls;
-	return r;
+	return kvm_skip_emulated_instruction(vcpu);
 }
 EXPORT_SYMBOL_GPL(kvm_emulate_hypercall);