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    Subject[tip:smp/hotplug] virt: Convert kvm hotplug to state machine
    Commit-ID:  8c18b2d2d0881b116ea52498c6d624c0a71e1fdc
    Gitweb: http://git.kernel.org/tip/8c18b2d2d0881b116ea52498c6d624c0a71e1fdc
    Author: Thomas Gleixner <tglx@linutronix.de>
    AuthorDate: Wed, 13 Jul 2016 17:16:37 +0000
    Committer: Ingo Molnar <mingo@kernel.org>
    CommitDate: Fri, 15 Jul 2016 10:40:23 +0200

    virt: Convert kvm hotplug to state machine

    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>
    Signed-off-by: Anna-Maria Gleixner <anna-maria@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
    Cc: rt@linutronix.de
    Link: http://lkml.kernel.org/r/20160713153335.886159080@linutronix.de
    Signed-off-by: Ingo Molnar <mingo@kernel.org>
    ---
    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 a5b6a65..5423997 100644
    --- a/include/linux/cpuhotplug.h
    +++ b/include/linux/cpuhotplug.h
    @@ -36,6 +36,7 @@ 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();
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