Messages in this thread | | | From | Paolo Bonzini <> | Subject | Re: [PATCH v2 5/8] KVM: x86: APICv: fix race in kvm_request_apicv_update on SVM | Date | Tue, 27 Jul 2021 00:34:54 +0200 |
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On 13/07/21 16:20, Maxim Levitsky wrote: > + mutex_lock(&vcpu->kvm->apicv_update_lock); > + > vcpu->arch.apicv_active = kvm_apicv_activated(vcpu->kvm); > kvm_apic_update_apicv(vcpu); > static_call(kvm_x86_refresh_apicv_exec_ctrl)(vcpu); > @@ -9246,6 +9248,8 @@ void kvm_vcpu_update_apicv(struct kvm_vcpu *vcpu) > */ > if (!vcpu->arch.apicv_active) > kvm_make_request(KVM_REQ_EVENT, vcpu); > + > + mutex_unlock(&vcpu->kvm->apicv_update_lock);
Does this whole piece of code need the lock/unlock? Does it work and/or make sense to do the unlock immediately after mutex_lock()? This makes it clearer that the mutex is being to synchronize against the requestor.
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index ed4d1581d502..ba5d5d9ebc64 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -943,6 +943,7 @@ static struct kvm *kvm_create_vm(unsigned long type) > mutex_init(&kvm->irq_lock); > mutex_init(&kvm->slots_lock); > mutex_init(&kvm->slots_arch_lock); > + mutex_init(&kvm->apicv_update_lock); > INIT_LIST_HEAD(&kvm->devices); > > BUILD_BUG_ON(KVM_MEM_SLOTS_NUM > SHRT_MAX); >
Please add comments above fields that are protected by this lock (anything but apicv_inhibit_reasons?), and especially move it to kvm->arch.
Paolo
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