On Thu, Dec 19, 2019 at 07:57:46AM -0800, Sean Christopherson wrote: > On Thu, Dec 19, 2019 at 04:28:15PM +0100, Frederic Weisbecker wrote: > > Hi, > > > > While checking the x86 async page fault code, I can't > > find anything that prevents KVM_PV_REASON_PAGE_READY to be injected > > while the guest has interrupts disabled. If that page fault happens > > to trap in an interrupt disabled section, there may be a deadlock due to the > > call to wake_up_process() which locks the rq->lock (among others). > > > > Given how long that code is there, I guess such an issue would > > have been reported for a while already. But I just would like to > > be sure we are checking that. > > > > Can someone enlighten me? > > The check is triggered from the caller of kvm_async_page_present(). > > kvm_check_async_pf_completion() > | > |-> kvm_arch_can_inject_async_page_present() > | > |-> kvm_can_do_async_pf() > | > |-> kvm_x86_ops->interrupt_allowed() Ah thanks, I missed that one. And what about kvm_async_page_present_sync()? I don't see a similar check there. And one last silly question, what about that line in kvm_arch_can_inject_async_page_present: if (!(vcpu->arch.apf.msr_val & KVM_ASYNC_PF_ENABLED)) return true; That looks weird, also it shortcuts the irqs_allowed() check. Thanks!
