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    SubjectRe: [PATCH v2 28/45] KVM: Use get/put_online_cpus_atomic() to prevent CPU offline
    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@redhat.com>
    > Cc: Paolo Bonzini <pbonzini@redhat.com>
    > Cc: kvm@vger.kernel.org
    > Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
    > ---
    >
    > 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 */
    >
    > --
    > To unsubscribe from this list: send the line "unsubscribe linux-pm" in
    > the body of a message to majordomo@vger.kernel.org
    > More majordomo info at http://vger.kernel.org/majordomo-info.html
    >

    Acked-by: Paolo Bonzini <pbonzini@redhat.com>



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