Re: [PATCH v2 3/5] target/arm: add descriptions of CLIDR_EL1, CCSIDR_EL1, CTR_EL0 to cpu.h

[Laurent Desnogues]

Hi Leif,

On Tue, Dec 15, 2020 at 5:49 PM Leif Lindholm <leif@nuviainc.com> wrote:
>
> On Tue, Dec 15, 2020 at 13:23:58 +0100, Laurent Desnogues wrote:
> > Hello,
> >
> > On Tue, Dec 15, 2020 at 12:51 PM Leif Lindholm <leif@nuviainc.com> wrote:
> > >
> > > Signed-off-by: Leif Lindholm <leif@nuviainc.com>
> > > ---
> > >  target/arm/cpu.h | 24 ++++++++++++++++++++++++
> > >  1 file changed, 24 insertions(+)
> > >
> > > diff --git a/target/arm/cpu.h b/target/arm/cpu.h
> > > index fadd1a47df..90ba707b64 100644
> > > --- a/target/arm/cpu.h
> > > +++ b/target/arm/cpu.h
> > > @@ -1736,6 +1736,30 @@ FIELD(V7M_FPCCR, ASPEN, 31, 1)
> > >  /*
> > >   * System register ID fields.
> > >   */
> > > +FIELD(CLIDR_EL1, CTYPE1, 0, 3)
> > > +FIELD(CLIDR_EL1, CTYPE2, 3, 3)
> > > +FIELD(CLIDR_EL1, CTYPE3, 6, 3)
> > > +FIELD(CLIDR_EL1, CTYPE4, 9, 3)
> > > +FIELD(CLIDR_EL1, CTYPE5, 12, 3)
> > > +FIELD(CLIDR_EL1, CTYPE6, 15, 3)
> > > +FIELD(CLIDR_EL1, CTYPE7, 18, 3)
> > > +FIELD(CLIDR_EL1, LOUIS, 21, 3)
> > > +FIELD(CLIDR_EL1, LOC, 24, 3)
> > > +FIELD(CLIDR_EL1, LOUU, 27, 3)
> > > +FIELD(CLIDR_EL1, ICB, 30, 3)
> > > +
> > > +FIELD(CCSIDR_EL1, LINESIZE, 0, 3)
> > > +FIELD(CCSIDR_EL1, ASSOCIATIVITY, 3, 21)
> > > +FIELD(CCSIDR_EL1, NUMSETS, 32, 24)
> >
> > The positions and sizes of the ASSOCIATIVITY and NUMSETS CCSIDR fields
> > depend on whether the ARMv8.3-CCIDX extension is implemented or not.
> > If we really want to define the fields this way, we perhaps should
> > define two sets.  Or at the very least, add a comment stating this
> > definition is for ARMv8.3-CCIDX.
>
> Urgh, sorry for this.
> I added the fields only to make the CPU definition more readable, so I
> think we don't need to worry about runtime handling of this?
> But I don't think it makes sense to add only the one form.
> Should I use CCIDX_CCSIDR_EL1 for these ones and add
>
> /* When FEAT_CCIDX is not implemented */
> FIELD(CCSIDR_EL1, LINESIZE, 0, 3)
> FIELD(CCSIDR_EL1, ASSOCIATIVITY, 3, 10)
> FIELD(CCSIDR_EL1, NUMSETS, 13, 15)
>
> with a comment that
> /* When FEAT_CCIDX is implemented */
> for the former set
> ?

Having both would be handy, but you need to have different names for
the fields.  For setting fields up in cpu{64}.c that'd be acceptable
as you know if the CPU you define has ARMv8.3-CCIDX. In the rest of
the code the use would be more complicated as you'd have to check for
ARMv8.3-CCIDX before accessing fields.  But the use of those fields
outside of cpu{64}.c would likely be extremely limited so I don't
think that's an issue.

> > > +FIELD(CTR_EL0,  IMINLINE, 0, 4)
> > > +FIELD(CTR_EL0,  L1IP, 14, 2)
> > > +FIELD(CTR_EL0,  DMINLINE, 16, 4)
> > > +FIELD(CTR_EL0,  ERG, 20, 4)
> > > +FIELD(CTR_EL0,  CWG, 24, 4)
> > > +FIELD(CTR_EL0,  IDC, 28, 1)
> > > +FIELD(CTR_EL0,  DIC, 29, 1)
> >
> > There's a missing field:  TminLine which starts at bit 32.
>
> Ack, oops.
>
> > If
> > implemented, that would require to make ctr a 64-bit integer.
>
> As far as I can tell, this will be safe with existing code - should I
> fold in a patch extending the register?

IMHO it'd be better to extend ctr to 64-bit.  But I'm not sure of the
implications in the rest of the code.

Thanks,

Laurent

> Regards,
>
> Leif
>
> > Thanks,
> >
> > Laurent
> >
> > > +
> > >  FIELD(MIDR_EL1, REVISION, 0, 4)
> > >  FIELD(MIDR_EL1, PARTNUM, 4, 12)
> > >  FIELD(MIDR_EL1, ARCHITECTURE, 16, 4)
> > > --
> > > 2.20.1
> > >
> > >