[Xen-devel] [patch 52/66] arm: xen: Convert to hotplug state machine

[Anna-Maria Gleixner <anna-maria@xxxxxxxxxxxxx>]

From: Richard Cochran <rcochran@xxxxxxxxxxxxx>

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@xxxxxxxxxxxxx>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Cc: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx
Signed-off-by: Anna-Maria Gleixner <anna-maria@xxxxxxxxxxxxx>
---
 arch/arm/xen/enlighten.c   |   41 +++++++++++------------------------------
 include/linux/cpuhotplug.h |    1 +
 2 files changed, 12 insertions(+), 30 deletions(-)

--- a/arch/arm/xen/enlighten.c
+++ b/arch/arm/xen/enlighten.c
@@ -161,12 +161,11 @@ static struct notifier_block xen_pvclock
        .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);
 
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -52,6 +52,7 @@ 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,



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