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.

Acked-by: Paolo Bonzini <pbonz...@redhat.com>
Cc: Gleb Natapov <g...@redhat.com>
Cc: kvm@vger.kernel.org
Signed-off-by: Srivatsa S. Bhat <srivatsa.b...@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 */

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