Re: [RFC PATCH v3 15/18] hw/arm/smmuv3: Advertise S2FWB

[Mostafa Saleh]

Hi Eric,

On Mon, May 20, 2024 at 03:30:58PM +0200, Eric Auger wrote:
> 
> 
> On 4/29/24 05:23, Mostafa Saleh wrote:
> > QEMU doesn's support memory attributes, so FWB is NOP, this
> > might change in the future if memory attributre would be supported.
> if mem attributes get supported
> >
> > Signed-off-by: Mostafa Saleh <smostafa@google.com>
> > ---
> >  hw/arm/smmuv3.c | 8 ++++++++
> >  1 file changed, 8 insertions(+)
> >
> > diff --git a/hw/arm/smmuv3.c b/hw/arm/smmuv3.c
> > index 88f6473d33..8a11e41144 100644
> > --- a/hw/arm/smmuv3.c
> > +++ b/hw/arm/smmuv3.c
> > @@ -287,6 +287,14 @@ static void smmuv3_init_regs(SMMUv3State *s)
> >      if (FIELD_EX32(s->idr[0], IDR0, S2P)) {
> >          /* XNX is a stage-2-specific feature */
> >          s->idr[3] = FIELD_DP32(s->idr[3], IDR3, XNX, 1);
> > +        if (FIELD_EX32(s->idr[0], IDR0, S1P)) {
> > +            /*
> > +             * QEMU doesn's support memory attributes, so FWB is NOP, this
> > +             * might change in the future if memory attributre would be
> if mem attributes get supported
> > +             * supported.
> > +             */
> > +           s->idr[3] = FIELD_DP32(s->idr[3], IDR3, FWB, 1);
> spec says:
> 0b0    Stage 2 control of memory types and attributes is
> not supported and the STE.S2FWB bit is RES 0.

My understanding it is still OK for the SMMU to advertise that although as
patch description indicates it is useless, but I thought it is similar to
XNX recently added, but I can drop it if it is not useful.

Thanks,
Mostafa
> 
> 
> Thanks
> 
> Eric
> > +        }
> >      }
> >      s->idr[3] = FIELD_DP32(s->idr[3], IDR3, RIL, 1);
> >      s->idr[3] = FIELD_DP32(s->idr[3], IDR3, BBML, 2);
>