Re: [PATCH v2 00/14] Unified cross-architecture kernel-mode FPU API

[Alex Deucher]

On Thu, Dec 28, 2023 at 5:11 AM Samuel Holland
<samuel.holland@xxxxxxxxxx> wrote:
>
> This series unifies the kernel-mode FPU API across several architectures
> by wrapping the existing functions (where needed) in consistently-named
> functions placed in a consistent header location, with mostly the same
> semantics: they can be called from preemptible or non-preemptible task
> context, and are not assumed to be reentrant. Architectures are also
> expected to provide CFLAGS adjustments for compiling FPU-dependent code.
> For the moment, SIMD/vector units are out of scope for this common API.
>
> This allows us to remove the ifdeffery and duplicated Makefile logic at
> each FPU user. It then implements the common API on RISC-V, and converts
> a couple of users to the new API: the AMDGPU DRM driver, and the FPU
> self test.
>
> The underlying goal of this series is to allow using newer AMD GPUs
> (e.g. Navi) on RISC-V boards such as SiFive's HiFive Unmatched. Those
> GPUs need CONFIG_DRM_AMD_DC_FP to initialize, which requires kernel-mode
> FPU support.

Series is:
Acked-by: Alex Deucher <alexander.deucher@xxxxxxx>

>
> Previous versions:
> v1: https://lore.kernel.org/linux-kernel/20231208055501.2916202-1-samuel.holland@xxxxxxxxxx/
> v0: https://lore.kernel.org/linux-kernel/20231122030621.3759313-1-samuel.holland@xxxxxxxxxx/
>
> Changes in v2:
>  - Add documentation explaining the built-time and runtime APIs
>  - Add a linux/fpu.h header for generic isolation enforcement
>  - Remove file name from header comment
>  - Clean up arch/arm64/lib/Makefile, like for arch/arm
>  - Remove RISC-V architecture-specific preprocessor check
>  - Split altivec removal to a separate patch
>  - Use linux/fpu.h instead of asm/fpu.h in consumers
>  - Declare test_fpu() in a header
>
> Michael Ellerman (1):
>   drm/amd/display: Only use hard-float, not altivec on powerpc
>
> Samuel Holland (13):
>   arch: Add ARCH_HAS_KERNEL_FPU_SUPPORT
>   ARM: Implement ARCH_HAS_KERNEL_FPU_SUPPORT
>   ARM: crypto: Use CC_FLAGS_FPU for NEON CFLAGS
>   arm64: Implement ARCH_HAS_KERNEL_FPU_SUPPORT
>   arm64: crypto: Use CC_FLAGS_FPU for NEON CFLAGS
>   lib/raid6: Use CC_FLAGS_FPU for NEON CFLAGS
>   LoongArch: Implement ARCH_HAS_KERNEL_FPU_SUPPORT
>   powerpc: Implement ARCH_HAS_KERNEL_FPU_SUPPORT
>   x86: Implement ARCH_HAS_KERNEL_FPU_SUPPORT
>   riscv: Add support for kernel-mode FPU
>   drm/amd/display: Use ARCH_HAS_KERNEL_FPU_SUPPORT
>   selftests/fpu: Move FP code to a separate translation unit
>   selftests/fpu: Allow building on other architectures
>
>  Documentation/core-api/floating-point.rst     | 78 +++++++++++++++++++
>  Documentation/core-api/index.rst              |  1 +
>  Makefile                                      |  5 ++
>  arch/Kconfig                                  |  6 ++
>  arch/arm/Kconfig                              |  1 +
>  arch/arm/Makefile                             |  7 ++
>  arch/arm/include/asm/fpu.h                    | 15 ++++
>  arch/arm/lib/Makefile                         |  3 +-
>  arch/arm64/Kconfig                            |  1 +
>  arch/arm64/Makefile                           |  9 ++-
>  arch/arm64/include/asm/fpu.h                  | 15 ++++
>  arch/arm64/lib/Makefile                       |  6 +-
>  arch/loongarch/Kconfig                        |  1 +
>  arch/loongarch/Makefile                       |  5 +-
>  arch/loongarch/include/asm/fpu.h              |  1 +
>  arch/powerpc/Kconfig                          |  1 +
>  arch/powerpc/Makefile                         |  5 +-
>  arch/powerpc/include/asm/fpu.h                | 28 +++++++
>  arch/riscv/Kconfig                            |  1 +
>  arch/riscv/Makefile                           |  3 +
>  arch/riscv/include/asm/fpu.h                  | 16 ++++
>  arch/riscv/kernel/Makefile                    |  1 +
>  arch/riscv/kernel/kernel_mode_fpu.c           | 28 +++++++
>  arch/x86/Kconfig                              |  1 +
>  arch/x86/Makefile                             | 20 +++++
>  arch/x86/include/asm/fpu.h                    | 13 ++++
>  drivers/gpu/drm/amd/display/Kconfig           |  2 +-
>  .../gpu/drm/amd/display/amdgpu_dm/dc_fpu.c    | 35 +--------
>  drivers/gpu/drm/amd/display/dc/dml/Makefile   | 36 +--------
>  drivers/gpu/drm/amd/display/dc/dml2/Makefile  | 36 +--------
>  include/linux/fpu.h                           | 12 +++
>  lib/Kconfig.debug                             |  2 +-
>  lib/Makefile                                  | 26 +------
>  lib/raid6/Makefile                            | 31 ++------
>  lib/test_fpu.h                                |  8 ++
>  lib/{test_fpu.c => test_fpu_glue.c}           | 37 ++-------
>  lib/test_fpu_impl.c                           | 37 +++++++++
>  37 files changed, 343 insertions(+), 190 deletions(-)
>  create mode 100644 Documentation/core-api/floating-point.rst
>  create mode 100644 arch/arm/include/asm/fpu.h
>  create mode 100644 arch/arm64/include/asm/fpu.h
>  create mode 100644 arch/powerpc/include/asm/fpu.h
>  create mode 100644 arch/riscv/include/asm/fpu.h
>  create mode 100644 arch/riscv/kernel/kernel_mode_fpu.c
>  create mode 100644 arch/x86/include/asm/fpu.h
>  create mode 100644 include/linux/fpu.h
>  create mode 100644 lib/test_fpu.h
>  rename lib/{test_fpu.c => test_fpu_glue.c} (71%)
>  create mode 100644 lib/test_fpu_impl.c
>
> --
> 2.42.0
>