Am Freitag, den 15.05.2020, 12:12 +0200 schrieb Paul Cercueil:
> 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.
Huh? Etnaviv patches are going through the etnaviv tree.
We now have two different solutions to the same issue. I first want to
dig into the code to see why two developers can get confused enough by
the code to come up with totally different fixes.
Regards,
Lucas
