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    Subject[PATCH 5.6 072/126] drm/etnaviv: fix perfmon domain interation
    Date
    From: Christian Gmeiner <christian.gmeiner@gmail.com>

    commit 40b697e256ccdb88aaff424b44b4d300eb8460e8 upstream.

    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@crapouillou.net>
    Tested-by: Paul Cercueil <paul@crapouillou.net>
    Fixes: ed1dd899baa3 ("drm/etnaviv: rework perfmon query infrastructure")
    Cc: stable@vger.kernel.org
    Signed-off-by: Christian Gmeiner <christian.gmeiner@gmail.com>
    Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/gpu/drm/etnaviv/etnaviv_perfmon.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    --- 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 *p
    if (!(gpu->identity.features & meta->feature))
    continue;

    - if (meta->nr_domains < (index - offset)) {
    + if (index - offset >= meta->nr_domains) {
    offset += meta->nr_domains;
    continue;
    }

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