KVM: x86: Do CPU compatibility checks in x86 code

Move the CPU compatibility checks to pure x86 code, i.e. drop x86's use
of the common kvm_x86_check_cpu_compat() arch hook.  x86 is the only
architecture that "needs" to do per-CPU compatibility checks, moving
the logic to x86 will allow dropping the common code, and will also
give x86 more control over when/how the compatibility checks are
performed, e.g. TDX will need to enable hardware (do VMXON) in order to
perform compatibility checks.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Isaku Yamahata <isaku.yamahata@intel.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Message-Id: <20221130230934.1014142-32-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/svm/svm.c

@@ -5109,7 +5109,7 @@ static int __init svm_init(void)
 	 * Common KVM initialization _must_ come last, after this, /dev/kvm is
 	 * exposed to userspace!
 	 */
-	r = kvm_init(&svm_init_ops, sizeof(struct vcpu_svm),
+	r = kvm_init(NULL, sizeof(struct vcpu_svm),
 		     __alignof__(struct vcpu_svm), THIS_MODULE);
 	if (r)
 		goto err_kvm_init;

arch/x86/kvm/vmx/vmx.c

@@ -8635,7 +8635,7 @@ static int __init vmx_init(void)
 	 * Common KVM initialization _must_ come last, after this, /dev/kvm is
 	 * exposed to userspace!
 	 */
-	r = kvm_init(&vmx_init_ops, sizeof(struct vcpu_vmx),
+	r = kvm_init(NULL, sizeof(struct vcpu_vmx),
 		     __alignof__(struct vcpu_vmx), THIS_MODULE);
 	if (r)
 		goto err_kvm_init;

arch/x86/kvm/x86.c

@@ -9292,10 +9292,36 @@ static inline void kvm_ops_update(struct kvm_x86_init_ops *ops)
 	kvm_pmu_ops_update(ops->pmu_ops);
 }
 
+struct kvm_cpu_compat_check {
+	struct kvm_x86_init_ops *ops;
+	int *ret;
+};
+
+static int kvm_x86_check_processor_compatibility(struct kvm_x86_init_ops *ops)
+{
+	struct cpuinfo_x86 *c = &cpu_data(smp_processor_id());
+
+	WARN_ON(!irqs_disabled());
+
+	if (__cr4_reserved_bits(cpu_has, c) !=
+	    __cr4_reserved_bits(cpu_has, &boot_cpu_data))
+		return -EIO;
+
+	return ops->check_processor_compatibility();
+}
+
+static void kvm_x86_check_cpu_compat(void *data)
+{
+	struct kvm_cpu_compat_check *c = data;
+
+	*c->ret = kvm_x86_check_processor_compatibility(c->ops);
+}
+
 static int __kvm_x86_vendor_init(struct kvm_x86_init_ops *ops)
 {
+	struct kvm_cpu_compat_check c;
 	u64 host_pat;
-	int r;
+	int r, cpu;
 
 	if (kvm_x86_ops.hardware_enable) {
 		pr_err("kvm: already loaded vendor module '%s'\n", kvm_x86_ops.name);
@@ -9375,6 +9401,14 @@ static int __kvm_x86_vendor_init(struct kvm_x86_init_ops *ops)
 	if (r != 0)
 		goto out_mmu_exit;
 
+	c.ret = &r;
+	c.ops = ops;
+	for_each_online_cpu(cpu) {
+		smp_call_function_single(cpu, kvm_x86_check_cpu_compat, &c, 1);
+		if (r < 0)
+			goto out_hardware_unsetup;
+	}
+
 	/*
 	 * Point of no return!  DO NOT add error paths below this point unless
 	 * absolutely necessary, as most operations from this point forward
@@ -9417,6 +9451,8 @@ static int __kvm_x86_vendor_init(struct kvm_x86_init_ops *ops)
 	kvm_init_msr_list();
 	return 0;
 
+out_hardware_unsetup:
+	ops->runtime_ops->hardware_unsetup();
 out_mmu_exit:
 	kvm_mmu_vendor_module_exit();
 out_free_percpu:
@@ -12050,16 +12086,7 @@ void kvm_arch_hardware_disable(void)
 
 int kvm_arch_check_processor_compat(void *opaque)
 {
-	struct cpuinfo_x86 *c = &cpu_data(smp_processor_id());
-	struct kvm_x86_init_ops *ops = opaque;
-
-	WARN_ON(!irqs_disabled());
-
-	if (__cr4_reserved_bits(cpu_has, c) !=
-	    __cr4_reserved_bits(cpu_has, &boot_cpu_data))
-		return -EIO;
-
-	return ops->check_processor_compatibility();
+	return 0;
 }
 
 bool kvm_vcpu_is_reset_bsp(struct kvm_vcpu *vcpu)