On Wed, Sep 27 2023, Halil Pasic <pasic@xxxxxxxxxxxxx> wrote: > On Wed, 27 Sep 2023 12:08:43 +0200 > Cornelia Huck <cohuck@xxxxxxxxxx> wrote: > >> > On the other hand virtio_airq_handler() calls vring_interrupt() with >> > interrupts enabled. (While vring_interrupt() is called in a (read) >> > critical section in virtio_airq_handler() we use read_lock() and >> > not read_lock_irqsave() to grab the lock. Whether that is correct in >> > it self (i.e. disregarding the crypto problem) or not I'm not sure right >> > now. Will think some more about it tomorrow.) If the way to go forward >> > is disabling interrupts in virtio-ccw before vring_interrupt() is >> > called, I would be glad to spin a patch for that. >> >> virtio_airq_handler() is supposed to be an interrupt handler for an >> adapter interrupt -- as such I would expect it to always run with >> interrupts disabled (and I'd expect vring_interrupt() to be called >> with interrupts disabled as well; if that's not the case, I think it >> would need to run asynchronously.) At least that was my understanding at >> the time I wrote the code. > > Thanks Connie! I don't quite understand what do you mean by "run with > interrupts disabled" in this context. > > Do you mean that if I were to add the following warning: > > diff --git a/drivers/s390/virtio/virtio_ccw.c b/drivers/s390/virtio/virtio_ccw.c > index ac67576301bf..2a9c73f5964f 100644 > --- a/drivers/s390/virtio/virtio_ccw.c > +++ b/drivers/s390/virtio/virtio_ccw.c > @@ -211,6 +211,8 @@ static void virtio_airq_handler(struct airq_struct *airq, > struct airq_info *info = container_of(airq, struct airq_info, airq); > unsigned long ai; > > + WARN_ONCE(in_irq(), "irqs are ought to be disabled but are not\n"); > + > inc_irq_stat(IRQIO_VAI); > > it would/should never trigger, or do you mean something different? > > If yes, does that mean that you would expect the common airq code (i.e. something > like do_airq_interrupt()) to disable interrupts, or call virtio_airq_handler()? > asynchronously sort of as a bottom half (my understanding of bottom halves is currently > not complete). > > If no what do you actually mean? My understanding (at the time) was that we're coming from the low-level interrupt handler (which disables interrupts via the NEW PSW); interrupts will be re-enabled once the basic processing is done. This might no longer be the case, but I currently don't have the time to dig into the code -- it has been some time.
