On Tue, May 11, 2021 at 10:39:11AM -0400, Peter Xu wrote:
> On Fri, May 07, 2021 at 07:08:31PM -0300, Marcelo Tosatti wrote:
> > > Wondering whether we should add a pi_test_on() check in kvm_vcpu_has_events()
> > > somehow, so that even without customized ->vcpu_check_block we should be able
> > > to break the block loop (as kvm_arch_vcpu_runnable will return true properly)?
> >
> > static int kvm_vcpu_check_block(struct kvm_vcpu *vcpu)
> > {
> > int ret = -EINTR;
> > int idx = srcu_read_lock(&vcpu->kvm->srcu);
> >
> > if (kvm_arch_vcpu_runnable(vcpu)) {
> > kvm_make_request(KVM_REQ_UNHALT, vcpu); <---
> > goto out;
> > }
> >
> > Don't want to unhalt the vcpu.
>
> Could you elaborate? It's not obvious to me why we can't do that if
> pi_test_on() returns true.. we have pending post interrupts anyways, so
> shouldn't we stop halting? Thanks!
pi_test_on() only returns true when an interrupt is signalled by the
device. But the sequence of events is:
1. pCPU idles without notification vector configured to wakeup vector.
2. PCI device is hotplugged, assigned device count increases from 0 to 1.
<arbitrary amount of time>
3. device generates interrupt, sets ON bit to true in the posted
interrupt descriptor.
We want to exit kvm_vcpu_block after 2, but before 3 (where ON bit
is not set).
