Re: XIVE VFIO kernel resample failure in INTx mode under heavy load

[Alexey Kardashevskiy]

On 14/04/2022 22:41, Cédric Le Goater wrote:
> > > After re-reading what I just wrote, I am leaning towards disabling 
> > > use of KVM_CAP_IRQFD_RESAMPLE as it seems last worked on POWER8 and 
> > > never since :)
> > >
> > > Did I miss something in the picture (hey Cedric)?
> >
> > How about disabling it like this?
> >
> > =====
> > diff --git a/hw/ppc/spapr_pci.c b/hw/ppc/spapr_pci.c
> > index 5bfd4aa9e5aa..c999f7b1ab1b 100644
> > --- a/hw/ppc/spapr_pci.c
> > +++ b/hw/ppc/spapr_pci.c
> > @@ -732,7 +732,7 @@ static PCIINTxRoute 
> > spapr_route_intx_pin_to_irq(void *opaque, int pin)
> >       SpaprPhbState *sphb = SPAPR_PCI_HOST_BRIDGE(opaque);
> >       PCIINTxRoute route;
> >
> > -    route.mode = PCI_INTX_ENABLED;
> > +    route.mode = PCI_INTX_DISABLED;
> >
> > =====
>
> I like it.


The only thing is that this resampling works on POWER8/XICS and removing 
it there is not great. So far sPAPR PHB was unaware of underlying 
interrupt controller, or was not it?


> You now know how to test all the combinations :) Prepare your matrix,
> variables are :
>
>   * Host OS        POWER8, POWER9+
>   * KVM device        XICS (P8), XICS-on-XIVE (P9), XIVE-on-XIVE (P9)
>   * kernel_irqchip    off, on
>   * ic-mode        xics, xive
>   * Guest OS        msi or nomsi
>
> Ideally you should check TCG, but that's like kernel_irqchip=off.
>
> Cheers,
>
> C.
>
> > (btw what the heck is PCI_INTX_INVERTED for?)
> >
> >
> > --
> > Alexey


--
Alexey