KVM: x86: Add a return value to kvm_emulate_cpuid

Once skipping the emulated instruction can potentially trigger an exit to
userspace (via KVM_GUESTDBG_SINGLESTEP) kvm_emulate_cpuid will need to
propagate a return value.

Signed-off-by: Kyle Huey <khuey@kylehuey.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>

arch/x86/include/asm/kvm_host.h

@@ -1134,7 +1134,7 @@ struct x86_emulate_ctxt;
 
 int kvm_fast_pio_out(struct kvm_vcpu *vcpu, int size, unsigned short port);
 int kvm_fast_pio_in(struct kvm_vcpu *vcpu, int size, unsigned short port);
-void kvm_emulate_cpuid(struct kvm_vcpu *vcpu);
+int kvm_emulate_cpuid(struct kvm_vcpu *vcpu);
 int kvm_emulate_halt(struct kvm_vcpu *vcpu);
 int kvm_vcpu_halt(struct kvm_vcpu *vcpu);
 int kvm_emulate_wbinvd(struct kvm_vcpu *vcpu);

arch/x86/kvm/cpuid.c

@@ -879,7 +879,7 @@ void kvm_cpuid(struct kvm_vcpu *vcpu, u32 *eax, u32 *ebx, u32 *ecx, u32 *edx)
 }
 EXPORT_SYMBOL_GPL(kvm_cpuid);
 
-void kvm_emulate_cpuid(struct kvm_vcpu *vcpu)
+int kvm_emulate_cpuid(struct kvm_vcpu *vcpu)
 {
 	u32 eax, ebx, ecx, edx;
 
@@ -891,5 +891,6 @@ void kvm_emulate_cpuid(struct kvm_vcpu *vcpu)
 	kvm_register_write(vcpu, VCPU_REGS_RCX, ecx);
 	kvm_register_write(vcpu, VCPU_REGS_RDX, edx);
 	kvm_x86_ops->skip_emulated_instruction(vcpu);
+	return 1;
 }
 EXPORT_SYMBOL_GPL(kvm_emulate_cpuid);

arch/x86/kvm/svm.c

@@ -3239,8 +3239,7 @@ static int task_switch_interception(struct vcpu_svm *svm)
 static int cpuid_interception(struct vcpu_svm *svm)
 {
 	svm->next_rip = kvm_rip_read(&svm->vcpu) + 2;
-	kvm_emulate_cpuid(&svm->vcpu);
-	return 1;
+	return kvm_emulate_cpuid(&svm->vcpu);
 }
 
 static int iret_interception(struct vcpu_svm *svm)

arch/x86/kvm/vmx.c

@@ -5837,8 +5837,7 @@ static void vmx_set_dr7(struct kvm_vcpu *vcpu, unsigned long val)
 
 static int handle_cpuid(struct kvm_vcpu *vcpu)
 {
-	kvm_emulate_cpuid(vcpu);
-	return 1;
+	return kvm_emulate_cpuid(vcpu);
 }
 
 static int handle_rdmsr(struct kvm_vcpu *vcpu)