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 <[email protected]>
Tested-by: Paul Cercueil <[email protected]>
Fixes: ed1dd899baa3 ("drm/etnaviv: rework perfmon query infrastructure")
Cc: [email protected]
Signed-off-by: Christian Gmeiner <[email protected]>
---
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
Hi Christian,
Am Montag, den 11.05.2020, 14:37 +0200 schrieb Christian Gmeiner:
> 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 <[email protected]>
> Tested-by: Paul Cercueil <[email protected]>
> Fixes: ed1dd899baa3 ("drm/etnaviv: rework perfmon query infrastructure")
> Cc: [email protected]
Missing last letter of the TLD.
> Signed-off-by: Christian Gmeiner <[email protected]>
> ---
> 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)) {
While the logic is correct, I find this quite hard to read. A more
idiomatic way to write this (which is much easier to grok when reading
the code IMHO) would be:
if (index - offset >= meta->nr_domains)
If you agree, please send a v2 of this patch.
Regards,
Lucas
> offset += meta->nr_domains;
> continue;
> }
Hi Lucas,
Am So., 17. Mai 2020 um 14:03 Uhr schrieb Lucas Stach <[email protected]>:
>
> Hi Christian,
>
> Am Montag, den 11.05.2020, 14:37 +0200 schrieb Christian Gmeiner:
> > 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 <[email protected]>
> > Tested-by: Paul Cercueil <[email protected]>
> > Fixes: ed1dd899baa3 ("drm/etnaviv: rework perfmon query infrastructure")
> > Cc: [email protected]
>
> Missing last letter of the TLD.
>
> > Signed-off-by: Christian Gmeiner <[email protected]>
> > ---
> > 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)) {
>
> While the logic is correct, I find this quite hard to read. A more
> idiomatic way to write this (which is much easier to grok when reading
> the code IMHO) would be:
>
> if (index - offset >= meta->nr_domains)
>
> If you agree, please send a v2 of this patch.
>
Works for me - will send a v2 in the evening.
--
greets
--
Christian Gmeiner, MSc
https://christian-gmeiner.info/privacypolicy