linux-kernel - [PATCH 5.15 131/262] drm/amd/display: Fix stream->link

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Message-Id: <20220307091706.156473293@linuxfoundation.org>
Date:   Mon,  7 Mar 2022 10:17:55 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Jimmy Kizito <Jimmy.Kizito@....com>,
        Jasdeep Dhillon <jdhillon@....com>,
        Nicholas Kazlauskas <nicholas.kazlauskas@....com>,
        Daniel Wheeler <daniel.wheeler@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.15 131/262] drm/amd/display: Fix stream->link_enc unassigned during stream removal

From: Nicholas Kazlauskas <nicholas.kazlauskas@....com>

[ Upstream commit 3743e7f6fcb938b7d8b7967e6a9442805e269b3d ]

[Why]
Found when running igt@..._atomic.

Userspace attempts to do a TEST_COMMIT when 0 streams which calls
dc_remove_stream_from_ctx. This in turn calls link_enc_unassign
which ends up modifying stream->link = NULL directly, causing the
global link_enc to be removed preventing further link activity
and future link validation from passing.

[How]
We take care of link_enc unassignment at the start of
link_enc_cfg_link_encs_assign so this call is no longer necessary.

Fixes global state from being modified while unlocked.

Reviewed-by: Jimmy Kizito <Jimmy.Kizito@....com>
Acked-by: Jasdeep Dhillon <jdhillon@....com>
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@....com>
Tested-by: Daniel Wheeler <daniel.wheeler@....com>
Signed-off-by: Alex Deucher <alexander.deucher@....com>
Cc: stable@...r.kernel.org
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/gpu/drm/amd/display/dc/core/dc_resource.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_resource.c b/drivers/gpu/drm/amd/display/dc/core/dc_resource.c
index e94546187cf15..7ae409f7dcf8d 100644
--- a/drivers/gpu/drm/amd/display/dc/core/dc_resource.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc_resource.c
@@ -1799,9 +1799,6 @@ enum dc_status dc_remove_stream_from_ctx(
 				dc->res_pool,
 			del_pipe->stream_res.stream_enc,
 			false);
-	/* Release link encoder from stream in new dc_state. */
-	if (dc->res_pool->funcs->link_enc_unassign)
-		dc->res_pool->funcs->link_enc_unassign(new_ctx, del_pipe->stream);
 
 	if (del_pipe->stream_res.audio)
 		update_audio_usage(
-- 
2.34.1