FAILED: patch "[PATCH] drm/amd/display: Wrap DCN32 phantom-plane allocation in" failed to apply to 6.12-stable tree

FAILED: patch "[PATCH] drm/amd/display: Wrap DCN32 phantom-plane allocation in" failed to apply to 6.12-stable tree

[gregkh]

The patch below does not apply to the 6.12-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.12.y
git checkout FETCH_HEAD
git cherry-pick -x 183182235f6d53bac62c6c39014738a54a68dfa6
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026052010-washbowl-cube-3ce9@gregkh' --subject-prefix 'PATCH 6.12.y' HEAD^..

Possible dependencies:



thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 183182235f6d53bac62c6c39014738a54a68dfa6 Mon Sep 17 00:00:00 2001
From: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com>
Date: Tue, 5 May 2026 09:05:37 +0800
Subject: [PATCH] drm/amd/display: Wrap DCN32 phantom-plane allocation in
 DC_RUN_WITH_PREEMPTION_ENABLED

[Why]
dcn32_validate_bandwidth() wraps dcn32_internal_validate_bw() with
DC_FP_START()/DC_FP_END(). In x86 non-RT, DC_FP_START takes fpregs_lock(),
which disables local softirqs.

The DML1 path through dcn32_enable_phantom_plane() calls kvzalloc() to
allocate ~335 KiB for dc_plane_state. This triggers the vmalloc path,
which calls BUG_ON(in_interrupt()) because it's invoked within the
FPU-enabled (softirq disabled) region, leading to a kernel crash.

[How]
Wrap the dc_state_create_phantom_plane() call with the
DC_RUN_WITH_PREEMPTION_ENABLED() macro to allow preemption during
this memory allocation.

Fixes: 235c67634230 ("drm/amd/display: add DCN32/321 specific files for Display Core")
Closes: https://gitlab.freedesktop.org/drm/amd/-/work_items/4470
Reviewed-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com>
Signed-off-by: James Lin <pinglei.lin@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 885ccbef7b94a8b38f69c4211c679021aa27ad11)
Cc: stable@vger.kernel.org

diff --git a/drivers/gpu/drm/amd/display/dc/resource/dcn32/dcn32_resource.c b/drivers/gpu/drm/amd/display/dc/resource/dcn32/dcn32_resource.c
index 82f81b586986..3751f7a94a05 100644
--- a/drivers/gpu/drm/amd/display/dc/resource/dcn32/dcn32_resource.c
+++ b/drivers/gpu/drm/amd/display/dc/resource/dcn32/dcn32_resource.c
@@ -92,9 +92,14 @@
 #include "dml/dcn32/dcn32_fpu.h"
 
 #include "dc_state_priv.h"
+#include "dc_fpu.h"
 
 #include "dml2_0/dml2_wrapper.h"
 
+#if !defined(DC_RUN_WITH_PREEMPTION_ENABLED)
+#define DC_RUN_WITH_PREEMPTION_ENABLED(code) code
+#endif
+
 #define DC_LOGGER_INIT(logger)
 
 enum dcn32_clk_src_array_id {
@@ -1684,7 +1689,8 @@ static void dcn32_enable_phantom_plane(struct dc *dc,
 		if (curr_pipe->top_pipe && curr_pipe->top_pipe->plane_state == curr_pipe->plane_state)
 			phantom_plane = prev_phantom_plane;
 		else
-			phantom_plane = dc_state_create_phantom_plane(dc, context, curr_pipe->plane_state);
+			DC_RUN_WITH_PREEMPTION_ENABLED(phantom_plane =
+				dc_state_create_phantom_plane(dc, context, curr_pipe->plane_state));
 
 		if (!phantom_plane)
 			continue;

[PATCH 6.12.y] drm/amd/display: Wrap DCN32 phantom-plane allocation in DC_RUN_WITH_PREEMPTION_ENABLED

[Mikhail Gavrilov]

[Why]
dcn32_validate_bandwidth() wraps dcn32_internal_validate_bw() with
DC_FP_START()/DC_FP_END(). In x86 non-RT, DC_FP_START takes fpregs_lock(),
which disables local softirqs.

The DML1 path through dcn32_enable_phantom_plane() calls kvzalloc() to
allocate ~335 KiB for dc_plane_state. This triggers the vmalloc path,
which calls BUG_ON(in_interrupt()) because it's invoked within the
FPU-enabled (softirq disabled) region, leading to a kernel crash.

[How]
Wrap the dc_state_create_phantom_plane() call with the
DC_RUN_WITH_PREEMPTION_ENABLED() macro to allow preemption during
this memory allocation.

Fixes: 235c67634230 ("drm/amd/display: add DCN32/321 specific files for Display Core")
Closes: https://gitlab.freedesktop.org/drm/amd/-/work_items/4470
Reviewed-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com>
Signed-off-by: James Lin <pinglei.lin@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 885ccbef7b94a8b38f69c4211c679021aa27ad11)
Cc: stable@vger.kernel.org
(cherry picked from commit 183182235f6d53bac62c6c39014738a54a68dfa6)
---
 .../drm/amd/display/dc/resource/dcn32/dcn32_resource.c    | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/display/dc/resource/dcn32/dcn32_resource.c b/drivers/gpu/drm/amd/display/dc/resource/dcn32/dcn32_resource.c
index ccfdca7c83f6..1fa4d32ce0be 100644
--- a/drivers/gpu/drm/amd/display/dc/resource/dcn32/dcn32_resource.c
+++ b/drivers/gpu/drm/amd/display/dc/resource/dcn32/dcn32_resource.c
@@ -90,9 +90,14 @@
 #include "dml/dcn32/dcn32_fpu.h"
 
 #include "dc_state_priv.h"
+#include "dc_fpu.h"
 
 #include "dml2/dml2_wrapper.h"
 
+#if !defined(DC_RUN_WITH_PREEMPTION_ENABLED)
+#define DC_RUN_WITH_PREEMPTION_ENABLED(code) code
+#endif
+
 #define DC_LOGGER_INIT(logger)
 
 enum dcn32_clk_src_array_id {
@@ -1649,7 +1654,8 @@ static void dcn32_enable_phantom_plane(struct dc *dc,
 		if (curr_pipe->top_pipe && curr_pipe->top_pipe->plane_state == curr_pipe->plane_state)
 			phantom_plane = prev_phantom_plane;
 		else
-			phantom_plane = dc_state_create_phantom_plane(dc, context, curr_pipe->plane_state);
+			DC_RUN_WITH_PREEMPTION_ENABLED(phantom_plane =
+				dc_state_create_phantom_plane(dc, context, curr_pipe->plane_state));
 
 		if (!phantom_plane)
 			continue;
-- 
2.54.0

Re: [PATCH 6.12.y] drm/amd/display: Wrap DCN32 phantom-plane allocation in DC_RUN_WITH_PREEMPTION_ENABLED

[Sasha Levin]

> [How]
> Wrap the dc_state_create_phantom_plane() call with the
> DC_RUN_WITH_PREEMPTION_ENABLED() macro to allow preemption during
> this memory allocation.

> +#if !defined(DC_RUN_WITH_PREEMPTION_ENABLED)
> +#define DC_RUN_WITH_PREEMPTION_ENABLED(code) code
> +#endif

Thanks for the backport, but this isn't going to fix the BUG_ON on
6.12.y as-is. DC_RUN_WITH_PREEMPTION_ENABLED() only gained its real
definition in v6.16 (around the dc_fpu_preempt rework); it does not
exist on 6.12 at all. With the "!defined(...) -> identity" fallback
above, the wrap reduces to a plain call to dc_state_create_phantom_plane()
on this tree, which is exactly the pre-patch code path that hits
BUG_ON(in_interrupt()) in the vmalloc path.

So the backport as written is a no-op on 6.12.y and won't address the
DCN32 crash you're seeing. To actually fix it on 6.12.y we need the
underlying preempt-enabled-region mechanism, or a different
6.12-specific fix that allows the ~335 KiB allocation outside the
DC_FP_START()/DC_FP_END() region (for example by hoisting the
allocation, or using a smaller/preallocated buffer).

Could you put together a v2 along those lines?

-- 
Thanks,
Sasha