In fact there is a race anyway:
if (cpu->exit_request) {
ret = 1;
break;
}
cpu->exit_request
SuspendThread
ResumeThread
hax_vcpu_interrupt(env);
qemu_mutex_unlock_iothread();
hax_ret = hax_vcpu_run(vcpu);
and the same race is true for QueueUserAPC. It's rare enough that I
guess we can accept the patches with just a FIXME comment, but... Yu
Ning, can you tell us what user_event_pending is for? :) My hunch is
that we should call hax_raise_event after setting cpu->exit_request, like
hax_raise_event();
/* write user_event_pending before exit_request */
smp_wmb();
cpu->exit_request = 1;
SuspendThread/ResumeThread
(or QueueUserAPC)
and in the hax thread:
if (cpu->exit_request) {
cpu->hax_vcpu->tunnel->user_event_pending = 0;
ret = 1;
break;
}
hax_vcpu_interrupt(env);
qemu_mutex_unlock_iothread();
/* read exit_request before user_event_pending */
smp_rmb();
hax_ret = hax_vcpu_run(vcpu);
but I would like some more official documentation than my own reverse
engineering of the brain of whoever wrote the interface (I have not
looked at the HAXM driver binary).