Re: [Qemu-devel] [PATCH v1 2/5] s390x/css: Use AIS AIRQ injection only if adapter support AIS

[Pierre Morel]

On 09/10/2017 10:17, Cornelia Huck wrote:
> On Wed,  4 Oct 2017 15:49:36 +0200
> Pierre Morel <address@hidden> wrote:
>
> > Testing to use Adapter Interrupt suppression or not depend on AIS
> > being enabled in the kernel.
> > To implement AIS emulation we must move this test inside the FLIC
> > dedicated irq_inject function.
> >
> > Furthermore, a test to verify that the adapter is subject to the AIS
> > must be added.
> >
> > Last, there is no need to crash QEMU if the injection failed, the
> > guest may recover from it.
> >
> > Signed-off-by: Pierre Morel <address@hidden>
> > ---
> >   hw/s390x/css.c | 6 ++++--
> >   1 file changed, 4 insertions(+), 2 deletions(-)
> >
> > diff --git a/hw/s390x/css.c b/hw/s390x/css.c
> > index 901dc6a..6e74a5c 100644
> > --- a/hw/s390x/css.c
> > +++ b/hw/s390x/css.c
> > @@ -672,10 +672,12 @@ void css_adapter_interrupt(CssIoAdapterType type, uint8_t 
> > isc)
> >       }
> >   
> >       trace_css_adapter_interrupt(isc);
> > -    if (fs->ais_supported) {
> > +    /* Use standard IRQ injection for adapters not supporting AIS */
>
> I'd move that comment to the else branch.

yes, clear.

> > +    if (adapter->flags & S390_ADAPTER_SUPPRESSIBLE) {
> > +        /* Use AIRQ injection for adapters subject to AIS */
> >           if (fsc->inject_airq(fs, type, isc, adapter->flags)) {
> >               error_report("Failed to inject airq with AIS supported");
> > -            exit(1);
> > +            /* Report error - guest will handle not receiving interrupts */
>
> I'm not 100% sure that this is the right thing to do. I have always
> operated under the assumption "if the hardware (host) accepts the I/O,
> it owes you an interrupt". (Don't the other failed interrupt injection
> paths do a hard stop as well? Is there any reasonable way for an
> injection failure to be transient?)

You are right and it is out of scope.
So I will let this untouch.

> >           }
> >       } else {
> >           s390_io_interrupt(0, 0, 0, io_int_word);


--
Pierre Morel
Linux/KVM/QEMU in Böblingen - Germany