x86/kvm: Make it compile on 32bit and with HYPYERVISOR_GUEST=n

The reenlightment support for hyperv slapped a direct reference to
x86_hyper_type into the kvm code which results in the following build
failure when CONFIG_HYPERVISOR_GUEST=n:

arch/x86/kvm/x86.c:6259:6: error: ‘x86_hyper_type’ undeclared (first use in this function)
arch/x86/kvm/x86.c:6259:6: note: each undeclared identifier is reported only once for each function it appears in

Use the proper helper function to cure that.

The 32bit compile fails because of:

arch/x86/kvm/x86.c:5936:13: warning: ‘kvm_hyperv_tsc_notifier’ defined but not used [-Wunused-function]

which is a real trainwreck engineering artwork. The callsite is wrapped
into #ifdef CONFIG_X86_64, but the function itself has the #ifdef inside
the function body. Make the function itself wrapped into the ifdef to cure
that.

Qualiteee....

Fixes: 0092e434 ("x86/kvm: Support Hyper-V reenlightenment")
Reported-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Stephen Hemminger <sthemmin@microsoft.com>
Cc: kvm@vger.kernel.org
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: "Michael Kelley (EOSG)" <Michael.H.Kelley@microsoft.com>
Cc: Roman Kagan <rkagan@virtuozzo.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: devel@linuxdriverproject.org
Cc: "K. Y. Srinivasan" <kys@microsoft.com>
Cc: Cathy Avery <cavery@redhat.com>
Cc: Mohammed Gamal <mmorsy@redhat.com>

arch/x86/kvm/x86.c

@@ -5933,9 +5933,9 @@ static void tsc_khz_changed(void *data)
 	__this_cpu_write(cpu_tsc_khz, khz);
 }
 
+#ifdef CONFIG_X86_64
 static void kvm_hyperv_tsc_notifier(void)
 {
-#ifdef CONFIG_X86_64
 	struct kvm *kvm;
 	struct kvm_vcpu *vcpu;
 	int cpu;
@@ -5967,8 +5967,8 @@ static void kvm_hyperv_tsc_notifier(void)
 		spin_unlock(&ka->pvclock_gtod_sync_lock);
 	}
 	spin_unlock(&kvm_lock);
-#endif
 }
+#endif
 
 static int kvmclock_cpufreq_notifier(struct notifier_block *nb, unsigned long val,
 				     void *data)
@@ -6256,7 +6256,7 @@ int kvm_arch_init(void *opaque)
 #ifdef CONFIG_X86_64
 	pvclock_gtod_register_notifier(&pvclock_gtod_notifier);
 
-	if (x86_hyper_type == X86_HYPER_MS_HYPERV)
+	if (hypervisor_is_type(X86_HYPER_MS_HYPERV))
 		set_hv_tscchange_cb(kvm_hyperv_tsc_notifier);
 #endif
 
@@ -6271,7 +6271,7 @@ int kvm_arch_init(void *opaque)
 void kvm_arch_exit(void)
 {
 #ifdef CONFIG_X86_64
-	if (x86_hyper_type == X86_HYPER_MS_HYPERV)
+	if (hypervisor_is_type(X86_HYPER_MS_HYPERV))
 		clear_hv_tscchange_cb();
 #endif
 	kvm_lapic_exit();