Re: [Qemu-devel] [PATCH] ioapic: allow buggy guests mishandling level-triggered interrupts to make progress

[Paolo Bonzini]

On 01/04/19 17:13, Vitaly Kuznetsov wrote:
>>> +                        trace_ioapic_eoi_delayed_reassert(vector);
>>> +                        timer_mod(s->timer,
>>> +                                  qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) +
>>> +                                  NANOSECONDS_PER_SECOND / 100);
>> Should this be done only if the timer isn't pending?
> Hm, maybe ... but how can this happen? To get here we need remote IRR
> bit and we clear it so someone needs to re-set it. The source won't
> probably be doing this (it is a level-triggered interrupt and it is
> already pending - why re-asserting?) but even if it does
> ioapic_service(s) will be called and when our timer fires we will just
> do nothing (consequitive ioapic_service() doesn't hurt).

Yeah, it's just for cleanliness.  Let's change it to
timer_mod_anticipate and call it a day.

Paolo