Re: [PATCH v3 3/3] powerpc/numa: Support coregroup on PowerNV

[Srikar Dronamraju <srikar@linux.ibm.com>]

* Shrikanth Hegde <sshegde@linux.ibm.com> [2026-09-04 15:34:50]:

Thanks Shrikanth for taking a look.

> 
> 
> On 9/2/26 6:05 PM, Srikar Dronamraju wrote:
> > Coregroup support on powerpc has so far been limited to PowerVM LPARs.
> > However, PowerNV can also support coregroups when firmware exposes the
> > required coregroup information through the associativity hierarchy.
> > 
> 
> Existing firmware does expose this info already?

The corresponding skiboot changes were sent to the skiboot mailing list.

> 
> > Detect coregroup support by checking whether primary_domain_index is the
> > penultimate domain in the CPU node's ibm,associativity property. On
> > PowerNV, a non-penultimate primary_domain_index indicates that firmware
> > provides an additional level for coregroup information.
> > 
> > This keeps the logic compatible with PowerVM systems, where
> > primary_domain_index is likewise not the penultimate associativity
> > domain.
> > 
> 
> Could you please put the ibm,associativity on this powernv? as well
> PowerVM's so that one understands it better?

With this patch and the skiboot change, the ibm,associativity will look
similar.

For example on a Power10 Baremetal box with skiboot changes.

$ lsprop /proc/device-tree/cpus/PowerPC,POWER10@*/ibm,associativity |& head -n 20
PowerPC,POWER10@0/ibm,associativity
		 00000005 00000000 00000000 00000000 00000000 00000000
PowerPC,POWER10@100/ibm,associativity
		 00000005 00000000 00000001 00000001 00000002 00000000
PowerPC,POWER10@108/ibm,associativity
		 00000005 00000000 00000001 00000001 00000002 00000002
PowerPC,POWER10@10/ibm,associativity
		 00000005 00000000 00000000 00000000 00000001 00000004
PowerPC,POWER10@110/ibm,associativity
		 00000005 00000000 00000001 00000001 00000003 00000004
PowerPC,POWER10@118/ibm,associativity
		 00000005 00000000 00000001 00000001 00000003 00000006
PowerPC,POWER10@120/ibm,associativity
		 00000005 00000000 00000001 00000001 00000002 00000008
PowerPC,POWER10@128/ibm,associativity
		 00000005 00000000 00000001 00000001 00000002 0000000a
PowerPC,POWER10@130/ibm,associativity
		 00000005 00000000 00000001 00000001 00000003 0000000c
PowerPC,POWER10@138/ibm,associativity
		 00000005 00000000 00000001 00000001 00000003 0000000e

> 
> > Signed-off-by: Srikar Dronamraju <srikar@linux.ibm.com>
> > ---
> > Changelog from v2:
> > - Handle comments from Ritesh (one hunk needed to be moved from patch 2 to
> >    patch 3 to build correctly)
> > 
> > Changelog from v1: https://lkml.kernel.org/r/20260524010017.140408-1-srikar@linux.ibm.com
> > - Handle comments from Christophe Leroy; make code more flat
> > 
> >   arch/powerpc/mm/numa.c | 58 ++++++++++++++++++++++++++++++++++--------
> >   1 file changed, 48 insertions(+), 10 deletions(-)

-- 
Thanks and Regards
Srikar Dronamraju