From mboxrd@z Thu Jan 1 00:00:00 1970 From: srivatsa.bhat@linux.vnet.ibm.com (Srivatsa S. Bhat) Date: Tue, 22 Jan 2013 13:10:13 +0530 Subject: [PATCH v5 27/45] KVM: Use get/put_online_cpus_atomic() to prevent CPU offline from atomic context In-Reply-To: <20130122073210.13822.50434.stgit@srivatsabhat.in.ibm.com> References: <20130122073210.13822.50434.stgit@srivatsabhat.in.ibm.com> Message-ID: <20130122074009.13822.3090.stgit@srivatsabhat.in.ibm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Once stop_machine() is gone from the CPU offline path, we won't be able to depend on preempt_disable() or local_irq_disable() 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: Marcelo Tosatti Cc: Gleb Natapov Cc: kvm at vger.kernel.org Signed-off-by: Srivatsa S. Bhat --- virt/kvm/kvm_main.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 1cd693a..47f9c30 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -174,7 +174,8 @@ static bool make_all_cpus_request(struct kvm *kvm, unsigned int req) zalloc_cpumask_var(&cpus, GFP_ATOMIC); - me = get_cpu(); + get_online_cpus_atomic(); + me = smp_processor_id(); kvm_for_each_vcpu(i, vcpu, kvm) { kvm_make_request(req, vcpu); cpu = vcpu->cpu; @@ -192,7 +193,7 @@ 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; } @@ -1621,11 +1622,12 @@ void kvm_vcpu_kick(struct kvm_vcpu *vcpu) ++vcpu->stat.halt_wakeup; } - me = get_cpu(); + get_online_cpus_atomic(); + me = smp_processor_id(); 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(); } #endif /* !CONFIG_S390 */