Re: [PATCH 2/2] EDAC/amd64: Mask UMC chip select to the four implemented selects

[Yazen Ghannam <yazen.ghannam@amd.com>]

On Fri, Sep 25, 2026 at 11:14:29AM -0700, Borislav Petkov wrote:
> On Fri, Sep 25, 2026 at 10:56:39PM +0530, Vishal Badole wrote:
> > umc_get_err_info() masks the Chip Select from MCA_SYND with 0x7, a
> > leftover from Zen 1 where the architecture reserved space for up to
> > eight chip selects. Only four have ever been implemented, and newer
> > products document this as MCA_SYND_UMC[1:0] = Chip Select.
> > 
> > Since only four csrows are allocated, a syndrome with bit 2 set decodes
> > to an out-of-range csrow and trips:
> > 
> >   EDAC MC0: INTERNAL ERROR: csrow value is out of range (5 >= 4)
> > 
> > Mask with 0x3 to match the four implemented chip selects.
> > 
> > Suggested-by: Yazen Ghannam <yazen.ghannam@amd.com>
> > Signed-off-by: Vishal Badole <Vishal.Badole@amd.com>
> > ---
> >  drivers/edac/amd64_edac.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/edac/amd64_edac.c b/drivers/edac/amd64_edac.c
> > index cab696be4f07..b69c3f51dd37 100644
> > --- a/drivers/edac/amd64_edac.c
> > +++ b/drivers/edac/amd64_edac.c
> > @@ -2802,7 +2802,7 @@ static inline void decode_bus_error(int node_id, struct mce *m)
> >  static void umc_get_err_info(struct mce *m, struct err_info *err)
> >  {
> >  	err->channel = (m->ipid & GENMASK(31, 0)) >> 20;
> > -	err->csrow = m->synd & 0x7;
> > +	err->csrow = m->synd & 0x3;
> >  }
> >  
> >  static void decode_umc_error(int node_id, struct mce *m)
> > -- 
> 
> Is this ever going to change?
> 
> Do we need to track this in the per-model struct, i.e., what your patch 1 is
> touching?

This works for everything up through Family 1Ah.

It *could* change in the future, but I don't want to speculate.

Also, I'm working on a fresh EDAC module without all the model-specific
stuff. This is the sort of thing it would avoid.

> 
> Is this a fix that needs to go to stable? If so, Fixes: tag and CC:stable.
> 
> If so, patches going to stable go first and need to be minimal for ease of
> backporting.
> 

I didn't consider this a necessary fix. But it'd be good to have it to
avoid noise from reports.

Vishal, please do add the 'Fixes:' tag, Cc stable, and reorder the
patches.

Otherwise, looks good.

Reviewed-by: Yazen Ghannam <yazen.ghannam@amd.com>

Thanks,
Yazen