[patch 35/66] virt: Convert kvm hotplug to state machine

[Anna-Maria Gleixner]

From: Thomas Gleixner <t...@linutronix.de>

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

Signed-off-by: Thomas Gleixner <t...@linutronix.de>
Reviewed-by: Sebastian Andrzej Siewior <bige...@linutronix.de>
Cc: Gleb Natapov <g...@kernel.org>
Cc: Paolo Bonzini <pbonz...@redhat.com>
Cc: k...@vger.kernel.org
Signed-off-by: Anna-Maria Gleixner <anna-ma...@linutronix.de>

---
 include/linux/cpuhotplug.h |    1 +
 virt/kvm/kvm_main.c        |   32 ++++++++------------------------
 2 files changed, 9 insertions(+), 24 deletions(-)

--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -37,6 +37,7 @@ 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,
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -3144,12 +3144,13 @@ static void hardware_enable_nolock(void
        }
 }
 
-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
        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
        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
                        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 @@ int kvm_init(void *opaque, unsigned vcpu
        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();