Il 25/06/2013 22:30, Srivatsa S. Bhat ha scritto:
> Once stop_machine() is gone from the CPU offline path, we won't be able
> to depend on disabling preemption to prevent CPUs from going offline
> from under us.
>
> Use the get/put_online_cpus_atomic() APIs to prevent CPUs from going
> offline, while invoking from atomic context.
>
> Cc: Gleb Natapov <gleb@xxxxxxxxxx>
> Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> Cc: kvm@xxxxxxxxxxxxxxx
> Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@xxxxxxxxxxxxxxxxxx>
> ---
>
> virt/kvm/kvm_main.c | 8 ++++----
> 1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 302681c..5bbfa30 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -174,7 +174,7 @@ static bool make_all_cpus_request(struct kvm *kvm, unsigned int req)
>
> zalloc_cpumask_var(&cpus, GFP_ATOMIC);
>
> - me = get_cpu();
> + me = get_online_cpus_atomic();
> kvm_for_each_vcpu(i, vcpu, kvm) {
> kvm_make_request(req, vcpu);
> cpu = vcpu->cpu;
> @@ -192,7 +192,7 @@ static bool make_all_cpus_request(struct kvm *kvm, unsigned int req)
> smp_call_function_many(cpus, ack_flush, NULL, 1);
> else
> called = false;
> - put_cpu();
> + put_online_cpus_atomic();
> free_cpumask_var(cpus);
> return called;
> }
> @@ -1707,11 +1707,11 @@ void kvm_vcpu_kick(struct kvm_vcpu *vcpu)
> ++vcpu->stat.halt_wakeup;
> }
>
> - me = get_cpu();
> + me = get_online_cpus_atomic();
> if (cpu != me && (unsigned)cpu < nr_cpu_ids && cpu_online(cpu))
> if (kvm_arch_vcpu_should_kick(vcpu))
> smp_send_reschedule(cpu);
> - put_cpu();
> + put_online_cpus_atomic();
> }
> EXPORT_SYMBOL_GPL(kvm_vcpu_kick);
> #endif /* !CONFIG_S390 */
>
> --
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>
Acked-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
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