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Subject[patch V2 36/67] virt: Convert kvm hotplug to state machine
From: Thomas Gleixner <tglx@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 <tglx@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
Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
---
include/linux/cpuhotplug.h | 1 +
virt/kvm/kvm_main.c | 32 ++++++++------------------------
2 files changed, 9 insertions(+), 24 deletions(-)

diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index 365d615..1d71f38 100644
--- 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,
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 48bd520..c1d6cf5 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();
--
2.8.1


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