Re: [PATCH] drm/etnaviv: fix perfmon domain interation

[Paul Cercueil <paul@xxxxxxxxxxxxxxx>]

Hi Christian,

Le ven. 15 mai 2020 à 12:09, Christian Gmeiner 
<christian.gmeiner@xxxxxxxxx> a écrit :
> Am Mo., 11. Mai 2020 um 14:38 Uhr schrieb Christian Gmeiner
> <christian.gmeiner@xxxxxxxxx>:
> >  The GC860 has one GPU device which has a 2d and 3d core. In this 
> > case
> >  we want to expose perfmon information for both cores.
> >
> >  The driver has one array which contains all possible perfmon domains
> >  with some meta data - doms_meta. Here we can see that for the GC860
> >  two elements of that array are relevant:
> >
> >    doms_3d: is at index 0 in the doms_meta array with 8 perfmon 
> > domains
> >    doms_2d: is at index 1 in the doms_meta array with 1 perfmon 
> > domain
> >
> >  The userspace driver wants to get a list of all perfmon domains and
> >  their perfmon signals. This is done by iterating over all domains 
> > and
> >  their signals. If the userspace driver wants to access the domain 
> > with
> >  id 8 the kernel driver fails and returns invalid data from doms_3d 
> > with
> >  and invalid offset.
> >
> >  This results in:
> >    Unable to handle kernel paging request at virtual address 00000000
> >
> >  On such a device it is not possible to use the userspace driver at 
> > all.
> >
> >  The fix for this off-by-one error is quite simple.
> >
> >  Reported-by: Paul Cercueil <paul@xxxxxxxxxxxxxxx>
> >  Tested-by: Paul Cercueil <paul@xxxxxxxxxxxxxxx>
> >  Fixes: ed1dd899baa3 ("drm/etnaviv: rework perfmon query 
> > infrastructure")
> >  Cc: stable@xxxxxxxxxxxxxxx
> >  Signed-off-by: Christian Gmeiner <christian.gmeiner@xxxxxxxxx>
> >  ---
> >   drivers/gpu/drm/etnaviv/etnaviv_perfmon.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> >  diff --git a/drivers/gpu/drm/etnaviv/etnaviv_perfmon.c 
> > b/drivers/gpu/drm/etnaviv/etnaviv_perfmon.c
> >  index e6795bafcbb9..35f7171e779a 100644
> >  --- a/drivers/gpu/drm/etnaviv/etnaviv_perfmon.c
> >  +++ b/drivers/gpu/drm/etnaviv/etnaviv_perfmon.c
> >  @@ -453,7 +453,7 @@ static const struct etnaviv_pm_domain 
> > *pm_domain(const struct etnaviv_gpu *gpu,
> >                  if (!(gpu->identity.features & meta->feature))
> >                          continue;
> >
> >  -               if (meta->nr_domains < (index - offset)) {
> >  +               if ((meta->nr_domains - 1) < (index - offset)) {
> >                          offset += meta->nr_domains;
> >                          continue;
> >                  }
> >  --
> >  2.26.2
>
> ping

I'll merge it tomorrow if there's no further feedback.

-Paul


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