KVM: x86: Add vendor name to kvm_x86_ops, use it for error messages

Paul pointed out the error messages when KVM fails to load are unhelpful
in understanding exactly what went wrong if userspace probes the "wrong"
module.

Add a mandatory kvm_x86_ops field to track vendor module names, kvm_intel
and kvm_amd, and use the name for relevant error message when KVM fails
to load so that the user knows which module failed to load.

Opportunistically tweak the "disabled by bios" error message to clarify
that _support_ was disabled, not that the module itself was magically
disabled by BIOS.

Suggested-by: Paul Menzel <pmenzel@molgen.mpg.de>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20211018183929.897461-2-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/include/asm/kvm_host.h

@@ -1301,6 +1301,8 @@ static inline u16 kvm_lapic_irq_dest_mode(bool dest_mode_logical)
 }
 
 struct kvm_x86_ops {
+	const char *name;
+
 	int (*hardware_enable)(void);
 	void (*hardware_disable)(void);
 	void (*hardware_unsetup)(void);

arch/x86/kvm/svm/svm.c

@@ -4580,6 +4580,8 @@ static int svm_vm_init(struct kvm *kvm)
 }
 
 static struct kvm_x86_ops svm_x86_ops __initdata = {
+	.name = "kvm_amd",
+
 	.hardware_unsetup = svm_hardware_teardown,
 	.hardware_enable = svm_hardware_enable,
 	.hardware_disable = svm_hardware_disable,

arch/x86/kvm/vmx/vmx.c

@@ -7570,6 +7570,8 @@ static bool vmx_check_apicv_inhibit_reasons(ulong bit)
 }
 
 static struct kvm_x86_ops vmx_x86_ops __initdata = {
+	.name = "kvm_intel",
+
 	.hardware_unsetup = hardware_unsetup,
 
 	.hardware_enable = hardware_enable,

arch/x86/kvm/x86.c

@@ -8532,18 +8532,20 @@ int kvm_arch_init(void *opaque)
 	int r;
 
 	if (kvm_x86_ops.hardware_enable) {
-		printk(KERN_ERR "kvm: already loaded the other module\n");
+		pr_err("kvm: already loaded vendor module '%s'\n", kvm_x86_ops.name);
 		r = -EEXIST;
 		goto out;
 	}
 
 	if (!ops->cpu_has_kvm_support()) {
-		pr_err_ratelimited("kvm: no hardware support\n");
+		pr_err_ratelimited("kvm: no hardware support for '%s'\n",
+				   ops->runtime_ops->name);
 		r = -EOPNOTSUPP;
 		goto out;
 	}
 	if (ops->disabled_by_bios()) {
-		pr_err_ratelimited("kvm: disabled by bios\n");
+		pr_err_ratelimited("kvm: support for '%s' disabled by bios\n",
+				   ops->runtime_ops->name);
 		r = -EOPNOTSUPP;
 		goto out;
 	}