KVM: Directly return result from kvm_arch_check_processor_compat()

Add a wrapper to invoke kvm_arch_check_processor_compat() so that the
boilerplate ugliness of checking virtualization support on all CPUs is
hidden from the arch specific code.  x86's implementation in particular
is quite heinous, as it unnecessarily propagates the out-param pattern
into kvm_x86_ops.

While the x86 specific issue could be resolved solely by changing
kvm_x86_ops, make the change for all architectures as returning a value
directly is prettier and technically more robust, e.g. s390 doesn't set
the out param, which could lead to subtle breakage in the (highly
unlikely) scenario where the out-param was not pre-initialized by the
caller.

Opportunistically annotate svm_check_processor_compat() with __init.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

4 files changed, 9 insertions, 9 deletions

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 450d69a1e6fa..d5457c7bb243 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -999,7 +999,7 @@ struct kvm_x86_ops {
 	int (*disabled_by_bios)(void);             /* __init */
 	int (*hardware_enable)(void);
 	void (*hardware_disable)(void);
-	void (*check_processor_compatibility)(void *rtn);
+	int (*check_processor_compatibility)(void);/* __init */
 	int (*hardware_setup)(void);               /* __init */
 	void (*hardware_unsetup)(void);            /* __exit */
 	bool (*cpu_has_accelerated_tpr)(void);
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index c56f40d430e5..302cb409d452 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -5871,9 +5871,9 @@ svm_patch_hypercall(struct kvm_vcpu *vcpu, unsigned char *hypercall)
 	hypercall[2] = 0xd9;
 }
 
-static void svm_check_processor_compat(void *rtn)
+static int __init svm_check_processor_compat(void)
 {
-	*(int *)rtn = 0;
+	return 0;
 }
 
 static bool svm_cpu_has_accelerated_tpr(void)
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index b35b3800a3c0..0861c71a4379 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -6733,22 +6733,22 @@ static int vmx_vm_init(struct kvm *kvm)
 	return 0;
 }
 
-static void __init vmx_check_processor_compat(void *rtn)
+static int __init vmx_check_processor_compat(void)
 {
 	struct vmcs_config vmcs_conf;
 	struct vmx_capability vmx_cap;
 
-	*(int *)rtn = 0;
 	if (setup_vmcs_config(&vmcs_conf, &vmx_cap) < 0)
-		*(int *)rtn = -EIO;
+		return -EIO;
 	if (nested)
 		nested_vmx_setup_ctls_msrs(&vmcs_conf.nested, vmx_cap.ept,
 					   enable_apicv);
 	if (memcmp(&vmcs_config, &vmcs_conf, sizeof(struct vmcs_config)) != 0) {
 		printk(KERN_ERR "kvm: CPU %d feature inconsistency!\n",
 				smp_processor_id());
-		*(int *)rtn = -EIO;
+		return -EIO;
 	}
+	return 0;
 }
 
 static u64 vmx_get_mt_mask(struct kvm_vcpu *vcpu, gfn_t gfn, bool is_mmio)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 2a713a74ca2e..5cb9ac9b61ab 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -9082,9 +9082,9 @@ void kvm_arch_hardware_unsetup(void)
 	kvm_x86_ops->hardware_unsetup();
 }
 
-void kvm_arch_check_processor_compat(void *rtn)
+int kvm_arch_check_processor_compat(void)
 {
-	kvm_x86_ops->check_processor_compatibility(rtn);
+	return kvm_x86_ops->check_processor_compatibility();
 }
 
 bool kvm_vcpu_is_reset_bsp(struct kvm_vcpu *vcpu)