Re: [PATCH v2] x86/cpufeatures: Add new cpuid features in SPR to featureset

["Alejandro Vallejo" <alejandro.vallejo@xxxxxxxxx>]

On Wed Aug 21, 2024 at 5:07 PM BST, Jan Beulich wrote:
> On 21.08.2024 17:34, Matthew Barnes wrote:
> > Upon running `xen-cpuid -v` on a host machine with Sapphire Rapids
> > within Dom0, there exist unrecognised features.
> > 
> > This patch adds these features as macros to the CPU featureset,
> > disabled by default.
> > 
> > Signed-off-by: Matthew Barnes <matthew.barnes@xxxxxxxxx>
>
> I don't strictly mind the patch in this shape, but ...
>
> > @@ -276,10 +283,13 @@ XEN_CPUFEATURE(TSX_FORCE_ABORT, 9*32+13) /* 
> > MSR_TSX_FORCE_ABORT.RTM_ABORT */
> >  XEN_CPUFEATURE(SERIALIZE,     9*32+14) /*A  SERIALIZE insn */
> >  XEN_CPUFEATURE(HYBRID,        9*32+15) /*   Heterogeneous platform */
> >  XEN_CPUFEATURE(TSXLDTRK,      9*32+16) /*a  TSX load tracking 
> > suspend/resume insns */
> > +XEN_CPUFEATURE(PCONFIG,       9*32+18) /*   PCONFIG insn */
> >  XEN_CPUFEATURE(ARCH_LBR,      9*32+19) /*   Architectural Last Branch 
> > Record */
> >  XEN_CPUFEATURE(CET_IBT,       9*32+20) /*   CET - Indirect Branch Tracking 
> > */
> > +XEN_CPUFEATURE(AMX_BF16,      9*32+22) /*   Tile computational operations 
> > on bfloat16 numbers */
> >  XEN_CPUFEATURE(AVX512_FP16,   9*32+23) /*A  AVX512 FP16 instructions */
> >  XEN_CPUFEATURE(AMX_TILE,      9*32+24) /*   AMX Tile architecture */
> > +XEN_CPUFEATURE(AMX_INT8,      9*32+25) /*   Tile computational operations 
> > on 8-bit integers */
> >  XEN_CPUFEATURE(IBRSB,         9*32+26) /*A  IBRS and IBPB support (used by 
> > Intel) */
> >  XEN_CPUFEATURE(STIBP,         9*32+27) /*A  STIBP */
> >  XEN_CPUFEATURE(L1D_FLUSH,     9*32+28) /*S  MSR_FLUSH_CMD and L1D flush. */
>
> ... having had a respective (more complete) patch pending for years I really
> wonder if it shouldn't be that one to be taken. While it would need adjustment
> to go ahead of other stuff (as posted in v3), I don't think it has any true
> dependency on earlier patches in the AMX series. IOW I could re-post v4
> standalone, and then we'd have a more complete view on AMX as well as proper
> dependencies in place.
>
> Thoughts?
>
> Jan

Oh! I had no idea you already posted patches to enable AMX. Is this the one?

https://lore.kernel.org/xen-devel/322de6db-e01f-0b57-5777-5d94a13c441a@xxxxxxxx/

Cheers,
Alejandro