From 40b697e256ccdb88aaff424b44b4d300eb8460e8 Mon Sep 17 00:00:00 2001
From: Christian Gmeiner <christian.gmeiner@gmail.com>
Date: Tue, 19 May 2020 07:30:15 +0200
Subject: drm/etnaviv: fix perfmon domain interation
Git-commit: 40b697e256ccdb88aaff424b44b4d300eb8460e8
Patch-mainline: v5.7-rc7
References: bsc#1113956

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>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
---
 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..75f9db8f7bec 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 (index - offset >= meta->nr_domains) {
 			offset += meta->nr_domains;
 			continue;
 		}
-- 
2.26.2