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

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Date:   Fri, 15 May 2020 12:09:57 +0200
From:   Christian Gmeiner <christian.gmeiner@...il.com>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Paul Cercueil <paul@...pouillou.net>, 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

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

-- 
greets
--
Christian Gmeiner, MSc

https://christian-gmeiner.info/privacypolicy