Re: [Qemu-devel] [Qemu-ppc] [PATCH] target/ppc/cpu-models: set POWER9_v1.0 as POWER9 DD1

[David Gibson]

On Wed, Jun 28, 2017 at 09:09:24AM +0200, Thomas Huth wrote:
> On 28.06.2017 03:42, address@hidden wrote:
> > On Fri, Jun 23, 2017 at 04:10:55PM +0200, Laurent Vivier wrote:
> >> On 23/06/2017 11:21, David Gibson wrote:
> >>> On Thu, Jun 22, 2017 at 01:31:24PM +0200, Thomas Huth wrote:
> >>>> On 22.06.2017 13:26, Laurent Vivier wrote:
> >>>>> CPU_POWERPC_POWER9_DD1 is 0x004E0100, so this is the POWER9 v1.0.
> >>>>>
> >>>>> When we run qemu on a POWER9 DD1 host, we must use either
> >>>>> "-cpu host" or "-cpu POWER9", but in the latter case it fails with
> >>>>>
> >>>>>     Unable to find sPAPR CPU Core definition
> >>>>>
> >>>>> because POWER9 DD1 doesn't appear in the list of known CPUs.
> >>>>>
> >>>>> This patch fixes this by defining POWER9_v1.0 with POWER9 DD1
> >>>>> PVR instead of CPU_POWERPC_POWER9_BASE.
> >>>>>
> >>>>> Signed-off-by: Laurent Vivier <address@hidden>
> >>>>> ---
> >>>>>  target/ppc/cpu-models.c | 2 +-
> >>>>>  1 file changed, 1 insertion(+), 1 deletion(-)
> >>>>>
> >>>>> diff --git a/target/ppc/cpu-models.c b/target/ppc/cpu-models.c
> >>>>> index 4d3e635..a22363c 100644
> >>>>> --- a/target/ppc/cpu-models.c
> >>>>> +++ b/target/ppc/cpu-models.c
> >>>>> @@ -1144,7 +1144,7 @@
> >>>>>      POWERPC_DEF("970_v2.2",      CPU_POWERPC_970_v22,                
> >>>>> 970,
> >>>>>                  "PowerPC 970 v2.2")
> >>>>>  
> >>>>> -    POWERPC_DEF("POWER9_v1.0",   CPU_POWERPC_POWER9_BASE,            
> >>>>> POWER9,
> >>>>> +    POWERPC_DEF("POWER9_v1.0",   CPU_POWERPC_POWER9_DD1,             
> >>>>> POWER9,
> >>>>>                  "POWER9 v1.0")
> >>>>>  
> >>>>>      POWERPC_DEF("970fx_v1.0",    CPU_POWERPC_970FX_v10,              
> >>>>> 970,
> >>>>>
> >>>>
> >>>> I think this also makes sense for running in TCG mode to get a valid
> >>>> real PVR there.
> >>>
> >>> I'm not so convinced.
> >>>
> >>> IIUC, this will make TCG default (for now) to a DD1 POWER9.  That's a)
> >>> probably not what anyone wants - who'd select a buggy prototype and b)
> >>> not accurate - TCG does not implement DD1's bugs.
> >>
> >> According to the POWER8 user manual (I didn't fine the POWER9 one):
> >>
> >> "3.6.3.1 Processor Version Register (PVR)
> >>
> >> The processor revision level (PVR[16:31]) starts at x‘0100’, indicating
> >> revision ‘1.0’. As revisions are made, bits [29:31] will indicate minor
> >> revisions. Similarly, bits [20:23] indicate major changes."
> >>
> >> POWER9 DD1 PVR is 0x004E0100, so this is really version 1.0 of the POWER9.
> >>
> >> Perhaps we can define POWER9_v1.0 as CPU_POWERPC_POWER9_DD1, and
> >> introduce a POWER9_v0.0 set to CPU_POWERPC_POWER9_BASE and define it as
> >> the default one?
> > 
> > I like the suggestion to set a v0.0 to CPU_POWERPC_POWER9_BASE. But, I
> > think we could have only that option, removing the
> > CPU_POWERPC_POWER9_DD1 entry.
> I really dislike the idea of having a CPU called "v0.0" ... we do not
> have this for any other CPU generation, and it sounds like it could be
> very confusing for the users (you'd need to document somewhere what the
> v0.0 exactly means). If we really want to go this way, I think we should
> name it "POWER9-generic" or "PowerISA-3.0" or something similar instead.
> 
> Or does somebody already know the exact PVR for DD2? If so, we could
> simply add a POWER9_v2.0 CPU already and let the POWER9 alias point to
> that version instead.

Yes, I think that's a better idea.  I don't know the DD2 PVR, but I'm
pretty sure we should be able to find out from someone at IBM.

I've CCed Sam & Suraj - can you ask Mikey or someone what the PVR
value for DD2.0 will be?

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

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