Re: [PATCH v2 2/3] spapr: Add SPAPR_CAP_AIL_MODE_3 for AIL mode 3 support for H_SET_MODE hcall

[Cédric Le Goater]

> > > > +    /* These tests match the CPU_FTR_P9_RADIX_PREFETCH_BUG flag in Linux */
> > > > +    if (((pcc->pvr & 0xffffff00) == CPU_POWERPC_POWER9_DD1) ||
> > > > +        ((pcc->pvr & 0xffffff00) == CPU_POWERPC_POWER9_DD20) ||
> > > > +        ((pcc->pvr & 0xffffff00) == CPU_POWERPC_POWER9_DD21)) {
> > > > +        return 0;
> > > > +    }
> > >
> > > Deducing what KVM supports rather than getting it to tell us
> > > explicitly with a cap is usually frowned upon.  However, given the
> > > earlier discussion, I'm satisfied that this is the least bad available
> > > option, at least for now.
> >
> > BTW this particular test doesn't work as I hoped because we only have
> > a power9 dd2.0 model.
>
> Oh.. yes... IIRC dd2.0 is barely present in the wild, since it doesn't
> have vital Spectre mitigations....
>
> > Adding a 2.2 or 2.3 would be possible. Maybe overkill.  I'll change
> > the test just to catch all POWER9 for now.
>
> ... no, given the above, I think we should definitely add the newer
> models.  Maybe even remove dd2.0 and replace it with the newer ones.

yes. It's really not a big effort.

Thanks,

C.