Re: [PATCH v2 5/7] spapr: TCG allow up to 8-thread SMT on POWER8 and newer CPUs

[Cédric Le Goater]

On 6/22/23 12:49, Cédric Le Goater wrote:
> On 6/22/23 12:06, Cédric Le Goater wrote:
> > On 6/22/23 11:33, Nicholas Piggin wrote:
> > > PPC TCG supports SMT CPU configurations for non-hypervisor state, so
> > > permit POWER8-10 pseries machines to enable SMT.
> > >
> > > This requires PIR and TIR be set, because that's how sibling thread
> > > matching is done by TCG.
> > >
> > > spapr's nested-HV capability does not currently coexist with SMT, so
> > > that combination is prohibited (interestingly somewhat analogous to
> > > LPAR-per-core mode on real hardware which also does not support KVM).
> > >
> > > Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
> > > ---
> > >   hw/ppc/spapr.c          | 16 ++++++++++++----
> > >   hw/ppc/spapr_caps.c     | 14 ++++++++++++++
> > >   hw/ppc/spapr_cpu_core.c |  7 +++++--
> > >   3 files changed, 31 insertions(+), 6 deletions(-)
> > >
> > > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> > > index 8e7d497f25..677b5eef9d 100644
> > > --- a/hw/ppc/spapr.c
> > > +++ b/hw/ppc/spapr.c
> > > @@ -2525,10 +2525,18 @@ static void spapr_set_vsmt_mode(SpaprMachineState 
> > > *spapr, Error **errp)
> > >       int ret;
> > >       unsigned int smp_threads = ms->smp.threads;
> > > -    if (tcg_enabled() && (smp_threads > 1)) {
> > > -        error_setg(errp, "TCG cannot support more than 1 thread/core "
> > > -                   "on a pseries machine");
> > > -        return;
> > > +    if (tcg_enabled()) {
>
> I will add :
>
>              if (smp_threads > 1 &&
>
> No need to resend for that.

and


Reviewed-by: Cédric Le Goater <clg@kaod.org>

Thanks,

C.