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

[Paolo Bonzini]

On 11/07/2016 14:28, Anna-Maria Gleixner wrote:
> From: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> 
> Install the callbacks via the state machine. The core won't invoke the
> callbacks on already online CPUs.
> 
> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Reviewed-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
> Cc: Gleb Natapov <gleb@xxxxxxxxxx>
> Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> Cc: kvm@xxxxxxxxxxxxxxx
> Signed-off-by: Anna-Maria Gleixner <anna-maria@xxxxxxxxxxxxx>
> 
> ---
>  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();
> 
> 
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Acked-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>