[PATCH] drm/amd: Permit DC_FP_START/END only in non-FP compilation units

[PATCH] drm/amd: Permit DC_FP_START/END only in non-FP compilation units

[Ard Biesheuvel]

From: Ard Biesheuvel <ardb@kernel.org>

Test the existing CPP macro _LINUX_FPU_COMPILATION_UNIT, which is set
when building source files that are permitted to use floating point,
in the implementation of DC_FP_START/END so that those are only usable
in non-FP code. This is a requirement of the generic kernel mode FPU
API, as some architectures (i.e., arm64) cannot safely enable FP codegen
in arbitrary code.

Cc: Austin Zheng <austin.zheng@amd.com>
Cc: Jun Lei <jun.lei@amd.com>
Cc: Harry Wentland <harry.wentland@amd.com>
Cc: Leo Li <sunpeng.li@amd.com>
Cc: Rodrigo Siqueira <siqueira@igalia.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: "Christian König" <christian.koenig@amd.com>
Cc: amd-gfx@lists.freedesktop.org
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.h | 8 ++++++++
 drivers/gpu/drm/amd/display/dc/os_types.h      | 2 --
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.h b/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.h
index b8275b397920..4e921632bc4e 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.h
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.h
@@ -31,4 +31,12 @@ void dc_assert_fp_enabled(void);
 void dc_fpu_begin(const char *function_name, const int line);
 void dc_fpu_end(const char *function_name, const int line);
 
+#ifndef _LINUX_FPU_COMPILATION_UNIT
+#define DC_FP_START()	dc_fpu_begin(__func__, __LINE__)
+#define DC_FP_END()	dc_fpu_end(__func__, __LINE__)
+#else
+#define DC_FP_START()	BUILD_BUG()
+#define DC_FP_END()	BUILD_BUG()
+#endif
+
 #endif /* __DC_FPU_H__ */
diff --git a/drivers/gpu/drm/amd/display/dc/os_types.h b/drivers/gpu/drm/amd/display/dc/os_types.h
index 782316348941..6af831710489 100644
--- a/drivers/gpu/drm/amd/display/dc/os_types.h
+++ b/drivers/gpu/drm/amd/display/dc/os_types.h
@@ -55,8 +55,6 @@
 
 #if defined(CONFIG_DRM_AMD_DC_FP)
 #include "amdgpu_dm/dc_fpu.h"
-#define DC_FP_START() dc_fpu_begin(__func__, __LINE__)
-#define DC_FP_END() dc_fpu_end(__func__, __LINE__)
 #endif /* CONFIG_DRM_AMD_DC_FP */
 
 /*
-- 
2.51.0.710.ga91ca5db03-goog

Re: [PATCH] drm/amd: Permit DC_FP_START/END only in non-FP compilation units

[Christian König]

On 09.10.25 17:06, Ard Biesheuvel wrote:
> From: Ard Biesheuvel <ardb@kernel.org>
> 
> Test the existing CPP macro _LINUX_FPU_COMPILATION_UNIT, which is set
> when building source files that are permitted to use floating point,
> in the implementation of DC_FP_START/END so that those are only usable
> in non-FP code. This is a requirement of the generic kernel mode FPU
> API, as some architectures (i.e., arm64) cannot safely enable FP codegen
> in arbitrary code.

If I'm not completely mistaken that is actually an issue on basically all architectures, at least x86 is affected as well if I'm not completely mistaken.

> Cc: Austin Zheng <austin.zheng@amd.com>
> Cc: Jun Lei <jun.lei@amd.com>
> Cc: Harry Wentland <harry.wentland@amd.com>
> Cc: Leo Li <sunpeng.li@amd.com>
> Cc: Rodrigo Siqueira <siqueira@igalia.com>
> Cc: Alex Deucher <alexander.deucher@amd.com>
> Cc: "Christian König" <christian.koenig@amd.com>
> Cc: amd-gfx@lists.freedesktop.org
> Cc: dri-devel@lists.freedesktop.org
> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

Anyway, patch looks sane to me but I'm not so deep in the DC code to fully judge.

Fell free to add Acked-by: Christian König <christian.koenig@amd.com>, but Harry and Leo need to take a look.

Thanks,
Christian.

> ---
>  drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.h | 8 ++++++++
>  drivers/gpu/drm/amd/display/dc/os_types.h      | 2 --
>  2 files changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.h b/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.h
> index b8275b397920..4e921632bc4e 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.h
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.h
> @@ -31,4 +31,12 @@ void dc_assert_fp_enabled(void);
>  void dc_fpu_begin(const char *function_name, const int line);
>  void dc_fpu_end(const char *function_name, const int line);
>  
> +#ifndef _LINUX_FPU_COMPILATION_UNIT
> +#define DC_FP_START()	dc_fpu_begin(__func__, __LINE__)
> +#define DC_FP_END()	dc_fpu_end(__func__, __LINE__)
> +#else
> +#define DC_FP_START()	BUILD_BUG()
> +#define DC_FP_END()	BUILD_BUG()
> +#endif
> +
>  #endif /* __DC_FPU_H__ */
> diff --git a/drivers/gpu/drm/amd/display/dc/os_types.h b/drivers/gpu/drm/amd/display/dc/os_types.h
> index 782316348941..6af831710489 100644
> --- a/drivers/gpu/drm/amd/display/dc/os_types.h
> +++ b/drivers/gpu/drm/amd/display/dc/os_types.h
> @@ -55,8 +55,6 @@
>  
>  #if defined(CONFIG_DRM_AMD_DC_FP)
>  #include "amdgpu_dm/dc_fpu.h"
> -#define DC_FP_START() dc_fpu_begin(__func__, __LINE__)
> -#define DC_FP_END() dc_fpu_end(__func__, __LINE__)
>  #endif /* CONFIG_DRM_AMD_DC_FP */
>  
>  /*

Re: [PATCH] drm/amd: Permit DC_FP_START/END only in non-FP compilation units

[Harry Wentland]

On 2025-10-09 12:19, Christian König wrote:
> On 09.10.25 17:06, Ard Biesheuvel wrote:
>> From: Ard Biesheuvel <ardb@kernel.org>
>>
>> Test the existing CPP macro _LINUX_FPU_COMPILATION_UNIT, which is set
>> when building source files that are permitted to use floating point,
>> in the implementation of DC_FP_START/END so that those are only usable
>> in non-FP code. This is a requirement of the generic kernel mode FPU
>> API, as some architectures (i.e., arm64) cannot safely enable FP codegen
>> in arbitrary code.
> 
> If I'm not completely mistaken that is actually an issue on basically all architectures, at least x86 is affected as well if I'm not completely mistaken.
> 
>> Cc: Austin Zheng <austin.zheng@amd.com>
>> Cc: Jun Lei <jun.lei@amd.com>
>> Cc: Harry Wentland <harry.wentland@amd.com>
>> Cc: Leo Li <sunpeng.li@amd.com>
>> Cc: Rodrigo Siqueira <siqueira@igalia.com>
>> Cc: Alex Deucher <alexander.deucher@amd.com>
>> Cc: "Christian König" <christian.koenig@amd.com>
>> Cc: amd-gfx@lists.freedesktop.org
>> Cc: dri-devel@lists.freedesktop.org
>> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> 
> Anyway, patch looks sane to me but I'm not so deep in the DC code to fully judge.
> 
> Fell free to add Acked-by: Christian König <christian.koenig@amd.com>, but Harry and Leo need to take a look.
> 

Thanks. Good safe-guard. Flags a bunch of issues in the
current code. Let me fix them before merging it.

Reviewed-by: Harry Wentland <harry.wentland@amd.com>

Harry

> Thanks,
> Christian.
> 
>> ---
>>  drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.h | 8 ++++++++
>>  drivers/gpu/drm/amd/display/dc/os_types.h      | 2 --
>>  2 files changed, 8 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.h b/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.h
>> index b8275b397920..4e921632bc4e 100644
>> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.h
>> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/dc_fpu.h
>> @@ -31,4 +31,12 @@ void dc_assert_fp_enabled(void);
>>  void dc_fpu_begin(const char *function_name, const int line);
>>  void dc_fpu_end(const char *function_name, const int line);
>>  
>> +#ifndef _LINUX_FPU_COMPILATION_UNIT
>> +#define DC_FP_START()	dc_fpu_begin(__func__, __LINE__)
>> +#define DC_FP_END()	dc_fpu_end(__func__, __LINE__)
>> +#else
>> +#define DC_FP_START()	BUILD_BUG()
>> +#define DC_FP_END()	BUILD_BUG()
>> +#endif
>> +
>>  #endif /* __DC_FPU_H__ */
>> diff --git a/drivers/gpu/drm/amd/display/dc/os_types.h b/drivers/gpu/drm/amd/display/dc/os_types.h
>> index 782316348941..6af831710489 100644
>> --- a/drivers/gpu/drm/amd/display/dc/os_types.h
>> +++ b/drivers/gpu/drm/amd/display/dc/os_types.h
>> @@ -55,8 +55,6 @@
>>  
>>  #if defined(CONFIG_DRM_AMD_DC_FP)
>>  #include "amdgpu_dm/dc_fpu.h"
>> -#define DC_FP_START() dc_fpu_begin(__func__, __LINE__)
>> -#define DC_FP_END() dc_fpu_end(__func__, __LINE__)
>>  #endif /* CONFIG_DRM_AMD_DC_FP */
>>  
>>  /*
> 

Re: [PATCH] drm/amd: Permit DC_FP_START/END only in non-FP compilation units

[Ard Biesheuvel]

On Thu, 9 Oct 2025 at 13:41, Harry Wentland <harry.wentland@amd.com> wrote:
>
>
>
> On 2025-10-09 12:19, Christian König wrote:
> > On 09.10.25 17:06, Ard Biesheuvel wrote:
> >> From: Ard Biesheuvel <ardb@kernel.org>
> >>
> >> Test the existing CPP macro _LINUX_FPU_COMPILATION_UNIT, which is set
> >> when building source files that are permitted to use floating point,
> >> in the implementation of DC_FP_START/END so that those are only usable
> >> in non-FP code. This is a requirement of the generic kernel mode FPU
> >> API, as some architectures (i.e., arm64) cannot safely enable FP codegen
> >> in arbitrary code.
> >
> > If I'm not completely mistaken that is actually an issue on basically all architectures, at least x86 is affected as well if I'm not completely mistaken.
> >
> >> Cc: Austin Zheng <austin.zheng@amd.com>
> >> Cc: Jun Lei <jun.lei@amd.com>
> >> Cc: Harry Wentland <harry.wentland@amd.com>
> >> Cc: Leo Li <sunpeng.li@amd.com>
> >> Cc: Rodrigo Siqueira <siqueira@igalia.com>
> >> Cc: Alex Deucher <alexander.deucher@amd.com>
> >> Cc: "Christian König" <christian.koenig@amd.com>
> >> Cc: amd-gfx@lists.freedesktop.org
> >> Cc: dri-devel@lists.freedesktop.org
> >> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> >
> > Anyway, patch looks sane to me but I'm not so deep in the DC code to fully judge.
> >
> > Fell free to add Acked-by: Christian König <christian.koenig@amd.com>, but Harry and Leo need to take a look.
> >
>
> Thanks. Good safe-guard. Flags a bunch of issues in the
> current code. Let me fix them before merging it.
>
> Reviewed-by: Harry Wentland <harry.wentland@amd.com>
>

Thanks.

I already fixed a bunch here:
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?id=ddbfac152830e38d488ff8e45ab7eaf5d72f8527

Re: [PATCH] drm/amd: Permit DC_FP_START/END only in non-FP compilation units

[kernel test robot]

Hi Ard,

kernel test robot noticed the following build errors:

[auto build test ERROR on soc/for-next]
[also build test ERROR on linus/master v6.17 next-20251010]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Ard-Biesheuvel/drm-amd-Permit-DC_FP_START-END-only-in-non-FP-compilation-units/20251010-120206
base:   https://git.kernel.org/pub/scm/linux/kernel/git/soc/soc.git for-next
patch link:    https://lore.kernel.org/r/20251009150621.3886079-2-ardb%2Bgit%40google.com
patch subject: [PATCH] drm/amd: Permit DC_FP_START/END only in non-FP compilation units
:::::: branch date: 14 hours ago
:::::: commit date: 14 hours ago
config: x86_64-randconfig-071-20251010 (https://download.01.org/0day-ci/archive/20251011/202510110219.Z6t2PJbZ-lkp@intel.com/config)
compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20251011/202510110219.Z6t2PJbZ-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/r/202510110219.Z6t2PJbZ-lkp@intel.com/

All errors (new ones prefixed by >>):

>> drivers/gpu/drm/amd/amdgpu/../display/dc/dml2/dml2_wrapper.c:563:2: error: call to '__compiletime_assert_610' declared with 'error' attribute: BUILD_BUG failed
     563 |         DC_FP_START();
         |         ^
   drivers/gpu/drm/amd/amdgpu/../display/amdgpu_dm/dc_fpu.h:38:23: note: expanded from macro 'DC_FP_START'
      38 | #define DC_FP_START()   BUILD_BUG()
         |                         ^
   include/linux/build_bug.h:59:21: note: expanded from macro 'BUILD_BUG'
      59 | #define BUILD_BUG() BUILD_BUG_ON_MSG(1, "BUILD_BUG failed")
         |                     ^
   include/linux/build_bug.h:39:37: note: expanded from macro 'BUILD_BUG_ON_MSG'
      39 | #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
         |                                     ^
   note: (skipping 1 expansions in backtrace; use -fmacro-backtrace-limit=0 to see all)
   include/linux/compiler_types.h:583:2: note: expanded from macro '_compiletime_assert'
     583 |         __compiletime_assert(condition, msg, prefix, suffix)
         |         ^
   include/linux/compiler_types.h:576:4: note: expanded from macro '__compiletime_assert'
     576 |                         prefix ## suffix();                             \
         |                         ^
   <scratch space>:39:1: note: expanded from here
      39 | __compiletime_assert_610
         | ^
   drivers/gpu/drm/amd/amdgpu/../display/dc/dml2/dml2_wrapper.c:615:2: error: call to '__compiletime_assert_612' declared with 'error' attribute: BUILD_BUG failed
     615 |         DC_FP_START();
         |         ^
   drivers/gpu/drm/amd/amdgpu/../display/amdgpu_dm/dc_fpu.h:38:23: note: expanded from macro 'DC_FP_START'
      38 | #define DC_FP_START()   BUILD_BUG()
         |                         ^
   include/linux/build_bug.h:59:21: note: expanded from macro 'BUILD_BUG'
      59 | #define BUILD_BUG() BUILD_BUG_ON_MSG(1, "BUILD_BUG failed")
         |                     ^
   include/linux/build_bug.h:39:37: note: expanded from macro 'BUILD_BUG_ON_MSG'
      39 | #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
         |                                     ^
   note: (skipping 1 expansions in backtrace; use -fmacro-backtrace-limit=0 to see all)
   include/linux/compiler_types.h:583:2: note: expanded from macro '_compiletime_assert'
     583 |         __compiletime_assert(condition, msg, prefix, suffix)
         |         ^
   include/linux/compiler_types.h:576:4: note: expanded from macro '__compiletime_assert'
     576 |                         prefix ## suffix();                             \
         |                         ^
   <scratch space>:45:1: note: expanded from here
      45 | __compiletime_assert_612
         | ^
   2 errors generated.


vim +563 drivers/gpu/drm/amd/amdgpu/../display/dc/dml2/dml2_wrapper.c

7966f319c66d94 Qingqing Zhuo    2023-07-28  547  
269c1d1443d668 Yan Li           2025-05-14  548  bool dml2_validate(const struct dc *in_dc, struct dc_state *context, struct dml2_context *dml2,
269c1d1443d668 Yan Li           2025-05-14  549  	enum dc_validate_mode validate_mode)
7966f319c66d94 Qingqing Zhuo    2023-07-28  550  {
7966f319c66d94 Qingqing Zhuo    2023-07-28  551  	bool out = false;
7966f319c66d94 Qingqing Zhuo    2023-07-28  552  
cc263c3a0c9f38 Joshua Aberback  2024-03-07  553  	if (!dml2)
7966f319c66d94 Qingqing Zhuo    2023-07-28  554  		return false;
cc263c3a0c9f38 Joshua Aberback  2024-03-07  555  	dml2_apply_debug_options(in_dc, dml2);
7966f319c66d94 Qingqing Zhuo    2023-07-28  556  
00c391102abc13 Aurabindo Pillai 2024-03-20  557  	/* DML2.1 validation path */
00c391102abc13 Aurabindo Pillai 2024-03-20  558  	if (dml2->architecture == dml2_architecture_21) {
269c1d1443d668 Yan Li           2025-05-14  559  		out = dml21_validate(in_dc, context, dml2, validate_mode);
00c391102abc13 Aurabindo Pillai 2024-03-20  560  		return out;
00c391102abc13 Aurabindo Pillai 2024-03-20  561  	}
7966f319c66d94 Qingqing Zhuo    2023-07-28  562  
366e77cd4923c3 Huacai Chen      2025-03-27 @563  	DC_FP_START();
366e77cd4923c3 Huacai Chen      2025-03-27  564  
269c1d1443d668 Yan Li           2025-05-14  565  	/* Use dml_validate_only for DC_VALIDATE_MODE_ONLY and DC_VALIDATE_MODE_AND_STATE_INDEX path */
269c1d1443d668 Yan Li           2025-05-14  566  	if (validate_mode != DC_VALIDATE_MODE_AND_PROGRAMMING)
b02b0fc488ba6e Yan Li           2025-05-21  567  		out = dml2_validate_only(context, validate_mode);
7966f319c66d94 Qingqing Zhuo    2023-07-28  568  	else
b02b0fc488ba6e Yan Li           2025-05-21  569  		out = dml2_validate_and_build_resource(in_dc, context, validate_mode);
366e77cd4923c3 Huacai Chen      2025-03-27  570  
366e77cd4923c3 Huacai Chen      2025-03-27  571  	DC_FP_END();
366e77cd4923c3 Huacai Chen      2025-03-27  572  
7966f319c66d94 Qingqing Zhuo    2023-07-28  573  	return out;
7966f319c66d94 Qingqing Zhuo    2023-07-28  574  }
7966f319c66d94 Qingqing Zhuo    2023-07-28  575  

-- 
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https://github.com/intel/lkp-tests/wiki