virt: Convert kvm hotplug to state machine

Install the callbacks via the state machine. The core won't invoke the
callbacks on already online CPUs.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Cc: Gleb Natapov <gleb@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Radim Krcmar <rkrcmar@redhat.com>
Cc: kvm@vger.kernel.org
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160713153335.886159080@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

2 files changed, 9 insertions, 24 deletions

diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index a5b6a6526af8..5423997c94f7 100644
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -36,6 +36,7 @@ enum cpuhp_state {
         CPUHP_AP_PERF_XTENSA_STARTING,
         CPUHP_AP_ARM_VFP_STARTING,
         CPUHP_AP_PERF_ARM_STARTING,
+        CPUHP_AP_KVM_STARTING,
         CPUHP_AP_NOTIFY_STARTING,
         CPUHP_AP_ONLINE,
         CPUHP_TEARDOWN_CPU,
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 48bd520fc702..c1d6cf5a74a1 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -3144,12 +3144,13 @@ static void hardware_enable_nolock(void *junk)
         }
 }
 
-static void hardware_enable(void)
+static int kvm_starting_cpu(unsigned int cpu)
 {
         raw_spin_lock(&kvm_count_lock);
         if (kvm_usage_count)
                 hardware_enable_nolock(NULL);
         raw_spin_unlock(&kvm_count_lock);
+        return 0;
 }
 
 static void hardware_disable_nolock(void *junk)
@@ -3162,12 +3163,13 @@ static void hardware_disable_nolock(void *junk)
         kvm_arch_hardware_disable();
 }
 
-static void hardware_disable(void)
+static int kvm_dying_cpu(unsigned int cpu)
 {
         raw_spin_lock(&kvm_count_lock);
         if (kvm_usage_count)
                 hardware_disable_nolock(NULL);
         raw_spin_unlock(&kvm_count_lock);
+        return 0;
 }
 
 static void hardware_disable_all_nolock(void)
@@ -3208,21 +3210,6 @@ static int hardware_enable_all(void)
         return r;
 }
 
-static int kvm_cpu_hotplug(struct notifier_block *notifier, unsigned long val,
-                           void *v)
-{
-        val &= ~CPU_TASKS_FROZEN;
-        switch (val) {
-        case CPU_DYING:
-                hardware_disable();
-                break;
-        case CPU_STARTING:
-                hardware_enable();
-                break;
-        }
-        return NOTIFY_OK;
-}
-
 static int kvm_reboot(struct notifier_block *notifier, unsigned long val,
                       void *v)
 {
@@ -3489,10 +3476,6 @@ int kvm_io_bus_unregister_dev(struct kvm *kvm, enum kvm_bus bus_idx,
         return r;
 }
 
-static struct notifier_block kvm_cpu_notifier = {
-        .notifier_call = kvm_cpu_hotplug,
-};
-
 static int kvm_debugfs_open(struct inode *inode, struct file *file,
                            int (*get)(void *, u64 *), int (*set)(void *, u64),
                            const char *fmt)
@@ -3743,7 +3726,8 @@ int kvm_init(void *opaque, unsigned vcpu_size, unsigned vcpu_align,
                         goto out_free_1;
         }
 
-        r = register_cpu_notifier(&kvm_cpu_notifier);
+        r = cpuhp_setup_state_nocalls(CPUHP_AP_KVM_STARTING, "AP_KVM_STARTING",
+                                      kvm_starting_cpu, kvm_dying_cpu);
         if (r)
                 goto out_free_2;
         register_reboot_notifier(&kvm_reboot_notifier);
@@ -3797,7 +3781,7 @@ out_free:
         kmem_cache_destroy(kvm_vcpu_cache);
 out_free_3:
         unregister_reboot_notifier(&kvm_reboot_notifier);
-        unregister_cpu_notifier(&kvm_cpu_notifier);
+        cpuhp_remove_state_nocalls(CPUHP_AP_KVM_STARTING);
 out_free_2:
 out_free_1:
         kvm_arch_hardware_unsetup();
@@ -3820,7 +3804,7 @@ void kvm_exit(void)
         kvm_async_pf_deinit();
         unregister_syscore_ops(&kvm_syscore_ops);
         unregister_reboot_notifier(&kvm_reboot_notifier);
-        unregister_cpu_notifier(&kvm_cpu_notifier);
+        cpuhp_remove_state_nocalls(CPUHP_AP_KVM_STARTING);
         on_each_cpu(hardware_disable_nolock, NULL, 1);
         kvm_arch_hardware_unsetup();
         kvm_arch_exit();