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SubjectRe: [patch V2 49/67] arm/xen: Convert to hotplug state machine
On Wed, 13 Jul 2016, Anna-Maria Gleixner wrote:
> From: Richard Cochran <rcochran@linutronix.de>
>
> Install the callbacks via the state machine and let the core invoke
> the callbacks on the already online CPUs.
>
> The get_cpu() in xen_starting_cpu() boils down to preempt_disable() since
> we already know the CPU we run on. Disabling preemption shouldn't be required
> here from what I see since it we don't switch CPUs while invoking the function.
>
> Signed-off-by: Richard Cochran <rcochran@linutronix.de>
> Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> Cc: Linus Torvalds <torvalds@linux-foundation.org>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Russell King <linux@armlinux.org.uk>
> Cc: Stefano Stabellini <sstabellini@kernel.org>
> Cc: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: linux-arm-kernel@lists.infradead.org
> Cc: xen-devel@lists.xenproject.org
> Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>

Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>


> arch/arm/xen/enlighten.c | 41 +++++++++++------------------------------
> include/linux/cpuhotplug.h | 1 +
> 2 files changed, 12 insertions(+), 30 deletions(-)
>
> diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
> index 75cd734..d822e23 100644
> --- a/arch/arm/xen/enlighten.c
> +++ b/arch/arm/xen/enlighten.c
> @@ -161,12 +161,11 @@ static struct notifier_block xen_pvclock_gtod_notifier = {
> .notifier_call = xen_pvclock_gtod_notify,
> };
>
> -static void xen_percpu_init(void)
> +static int xen_starting_cpu(unsigned int cpu)
> {
> struct vcpu_register_vcpu_info info;
> struct vcpu_info *vcpup;
> int err;
> - int cpu = get_cpu();
>
> /*
> * VCPUOP_register_vcpu_info cannot be called twice for the same
> @@ -190,7 +189,13 @@ static void xen_percpu_init(void)
>
> after_register_vcpu_info:
> enable_percpu_irq(xen_events_irq, 0);
> - put_cpu();
> + return 0;
> +}
> +
> +static int xen_dying_cpu(unsigned int cpu)
> +{
> + disable_percpu_irq(xen_events_irq);
> + return 0;
> }
>
> static void xen_restart(enum reboot_mode reboot_mode, const char *cmd)
> @@ -209,28 +214,6 @@ static void xen_power_off(void)
> BUG_ON(rc);
> }
>
> -static int xen_cpu_notification(struct notifier_block *self,
> - unsigned long action,
> - void *hcpu)
> -{
> - switch (action) {
> - case CPU_STARTING:
> - xen_percpu_init();
> - break;
> - case CPU_DYING:
> - disable_percpu_irq(xen_events_irq);
> - break;
> - default:
> - break;
> - }
> -
> - return NOTIFY_OK;
> -}
> -
> -static struct notifier_block xen_cpu_notifier = {
> - .notifier_call = xen_cpu_notification,
> -};
> -
> static irqreturn_t xen_arm_callback(int irq, void *arg)
> {
> xen_hvm_evtchn_do_upcall();
> @@ -351,16 +334,14 @@ static int __init xen_guest_init(void)
> return -EINVAL;
> }
>
> - xen_percpu_init();
> -
> - register_cpu_notifier(&xen_cpu_notifier);
> -
> pv_time_ops.steal_clock = xen_stolen_accounting;
> static_key_slow_inc(&paravirt_steal_enabled);
> if (xen_initial_domain())
> pvclock_gtod_register_notifier(&xen_pvclock_gtod_notifier);
>
> - return 0;
> + return cpuhp_setup_state(CPUHP_AP_ARM_XEN_STARTING,
> + "AP_ARM_XEN_STARTING", xen_starting_cpu,
> + xen_dying_cpu);
> }
> early_initcall(xen_guest_init);
>
> diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
> index 86ac982..f986963 100644
> --- a/include/linux/cpuhotplug.h
> +++ b/include/linux/cpuhotplug.h
> @@ -48,6 +48,7 @@ enum cpuhp_state {
> CPUHP_AP_KVM_STARTING,
> CPUHP_AP_KVM_ARM_VGIC_STARTING,
> CPUHP_AP_KVM_ARM_TIMER_STARTING,
> + CPUHP_AP_ARM_XEN_STARTING,
> CPUHP_AP_LEDTRIG_STARTING,
> CPUHP_AP_NOTIFY_STARTING,
> CPUHP_AP_ONLINE,
> --
> 2.8.1
>
>
>

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