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

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Message-ID: <CAH9NwWcjrd2cNrVpMaHQPyrwzKASetGXcb=sjA4VDThyV6h5Vg@mail.gmail.com>
Date:   Fri, 15 May 2020 12:26:09 +0200
From:   Christian Gmeiner <christian.gmeiner@...il.com>
To:     Paul Cercueil <paul@...pouillou.net>
Cc:     LKML <linux-kernel@...r.kernel.org>, stable@...r.kernel.org,
        Lucas Stach <l.stach@...gutronix.de>,
        Russell King <linux+etnaviv@...linux.org.uk>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        The etnaviv authors <etnaviv@...ts.freedesktop.org>,
        DRI mailing list <dri-devel@...ts.freedesktop.org>
Subject: Re: [PATCH] drm/etnaviv: fix perfmon domain interation

Hi Paul

Am Fr., 15. Mai 2020 um 12:12 Uhr schrieb Paul Cercueil <paul@...pouillou.net>:
>
> Hi Christian,
>
> Le ven. 15 mai 2020 à 12:09, Christian Gmeiner
> <christian.gmeiner@...il.com> a écrit :
> > Am Mo., 11. Mai 2020 um 14:38 Uhr schrieb Christian Gmeiner
> > <christian.gmeiner@...il.com>:
> >>
> >>  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@...pouillou.net>
> >>  Tested-by: Paul Cercueil <paul@...pouillou.net>
> >>  Fixes: ed1dd899baa3 ("drm/etnaviv: rework perfmon query
> >> infrastructure")
> >>  Cc: stable@...r.kernel.org
> >>  Signed-off-by: Christian Gmeiner <christian.gmeiner@...il.com>
> >>  ---
> >>   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.
>

Works for me too.. as far as Lucas (the maintainer) is happy with it.

-- 
greets
--
Christian Gmeiner, MSc

https://christian-gmeiner.info/privacypolicy