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>

11 files changed, 27 insertions, 20 deletions

diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c
index 0369f26ab96d..2cfe839f0b3a 100644
--- a/arch/mips/kvm/mips.c
+++ b/arch/mips/kvm/mips.c
@@ -123,9 +123,9 @@ int kvm_arch_hardware_setup(void)
 	return 0;
 }
 
-void kvm_arch_check_processor_compat(void *rtn)
+int kvm_arch_check_processor_compat(void)
 {
-	*(int *)rtn = 0;
+	return 0;
 }
 
 int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index aa3a678711be..628d3c791ad7 100644
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -425,9 +425,9 @@ int kvm_arch_hardware_setup(void)
 	return 0;
 }
 
-void kvm_arch_check_processor_compat(void *rtn)
+int kvm_arch_check_processor_compat(void)
 {
-	*(int *)rtn = kvmppc_core_check_processor_compat();
+	return kvmppc_core_check_processor_compat();
 }
 
 int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
index 2b00a3ebee08..da5825a3c16b 100644
--- a/arch/s390/include/asm/kvm_host.h
+++ b/arch/s390/include/asm/kvm_host.h
@@ -905,7 +905,6 @@ extern int kvm_s390_gisc_register(struct kvm *kvm, u32 gisc);
 extern int kvm_s390_gisc_unregister(struct kvm *kvm, u32 gisc);
 
 static inline void kvm_arch_hardware_disable(void) {}
-static inline void kvm_arch_check_processor_compat(void *rtn) {}
 static inline void kvm_arch_sync_events(struct kvm *kvm) {}
 static inline void kvm_arch_vcpu_uninit(struct kvm_vcpu *vcpu) {}
 static inline void kvm_arch_sched_in(struct kvm_vcpu *vcpu, int cpu) {}
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 28ebd647784c..7936af0a971f 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -227,6 +227,11 @@ int kvm_arch_hardware_enable(void)
 	return 0;
 }
 
+int kvm_arch_check_processor_compat(void)
+{
+	return 0;
+}
+
 static void kvm_gmap_notifier(struct gmap *gmap, unsigned long start,
 			      unsigned long end);
 
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)
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 79fa4426509c..5e9fd7ad8018 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -870,7 +870,7 @@ int kvm_arch_hardware_enable(void);
 void kvm_arch_hardware_disable(void);
 int kvm_arch_hardware_setup(void);
 void kvm_arch_hardware_unsetup(void);
-void kvm_arch_check_processor_compat(void *rtn);
+int kvm_arch_check_processor_compat(void);
 int kvm_arch_vcpu_runnable(struct kvm_vcpu *vcpu);
 bool kvm_arch_vcpu_in_kernel(struct kvm_vcpu *vcpu);
 int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu);
diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
index 7eeebe5e9da2..d2389033e9d6 100644
--- a/virt/kvm/arm/arm.c
+++ b/virt/kvm/arm/arm.c
@@ -105,9 +105,9 @@ int kvm_arch_hardware_setup(void)
 	return 0;
 }
 
-void kvm_arch_check_processor_compat(void *rtn)
+int kvm_arch_check_processor_compat(void)
 {
-	*(int *)rtn = 0;
+	return 0;
 }
 
 
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index ca54b09adf5b..b2579841263f 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -4224,6 +4224,11 @@ static void kvm_sched_out(struct preempt_notifier *pn,
 	kvm_arch_vcpu_put(vcpu);
 }
 
+static void check_processor_compat(void *rtn)
+{
+	*(int *)rtn = kvm_arch_check_processor_compat();
+}
+
 int kvm_init(void *opaque, unsigned vcpu_size, unsigned vcpu_align,
 		  struct module *module)
 {
@@ -4255,9 +4260,7 @@ int kvm_init(void *opaque, unsigned vcpu_size, unsigned vcpu_align,
 		goto out_free_0a;
 
 	for_each_online_cpu(cpu) {
-		smp_call_function_single(cpu,
-				kvm_arch_check_processor_compat,
-				&r, 1);
+		smp_call_function_single(cpu, check_processor_compat, &r, 1);
 		if (r < 0)
 			goto out_free_1;
 	}