Unified cross-architecture kernel-mode FPU API #803
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Several architectures provide an API to enable the FPU and run floating-point SIMD code in kernel space. However, the function names, header locations, and semantics are inconsistent across architectures, and FPU support may be gated behind other Kconfig options. Provide a standard way for architectures to declare that kernel space FPU support is available. Architectures selecting this option must implement what is currently the most common API (kernel_fpu_begin() and kernel_fpu_end(), plus a new function kernel_fpu_available()) and provide the appropriate CFLAGS for compiling floating-point C code. Suggested-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Samuel Holland <samuel.holland@sifive.com> Signed-off-by: Björn Töpel <bjorn@rivosinc.com>
ARM provides an equivalent to the common kernel-mode FPU API, but in a different header and using different function names. Add a wrapper header, and export CFLAGS adjustments as found in lib/raid6/Makefile. Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Samuel Holland <samuel.holland@sifive.com> Signed-off-by: Björn Töpel <bjorn@rivosinc.com>
Now that CC_FLAGS_FPU is exported and can be used anywhere in the source tree, use it instead of duplicating the flags here. Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Samuel Holland <samuel.holland@sifive.com> Signed-off-by: Björn Töpel <bjorn@rivosinc.com>
arm64 provides an equivalent to the common kernel-mode FPU API, but in a different header and using different function names. Add a wrapper header, and export CFLAGS adjustments as found in lib/raid6/Makefile. Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Samuel Holland <samuel.holland@sifive.com> Signed-off-by: Björn Töpel <bjorn@rivosinc.com>
Now that CC_FLAGS_FPU is exported and can be used anywhere in the source tree, use it instead of duplicating the flags here. Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Samuel Holland <samuel.holland@sifive.com> Signed-off-by: Björn Töpel <bjorn@rivosinc.com>
Now that CC_FLAGS_FPU is exported and can be used anywhere in the source tree, use it instead of duplicating the flags here. Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Samuel Holland <samuel.holland@sifive.com> Signed-off-by: Björn Töpel <bjorn@rivosinc.com>
LoongArch already provides kernel_fpu_begin() and kernel_fpu_end() in asm/fpu.h, so it only needs to add kernel_fpu_available() and export the CFLAGS adjustments. Acked-by: WANG Xuerui <git@xen0n.name> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Samuel Holland <samuel.holland@sifive.com> Signed-off-by: Björn Töpel <bjorn@rivosinc.com>
PowerPC provides an equivalent to the common kernel-mode FPU API, but in a different header and using different function names. The PowerPC API also requires a non-preemptible context. Add a wrapper header, and export the CFLAGS adjustments. Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc) Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Samuel Holland <samuel.holland@sifive.com> Signed-off-by: Björn Töpel <bjorn@rivosinc.com>
The include guard should match the filename, or it will conflict with the newly-added asm/fpu.h. Signed-off-by: Samuel Holland <samuel.holland@sifive.com> Acked-by: Dave Hansen <dave.hansen@linux.intel.com> Signed-off-by: Björn Töpel <bjorn@rivosinc.com>
x86 already provides kernel_fpu_begin() and kernel_fpu_end(), but in a different header. Add a wrapper header, and export the CFLAGS adjustments as found in lib/Makefile. Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Samuel Holland <samuel.holland@sifive.com> Signed-off-by: Björn Töpel <bjorn@rivosinc.com>
This is motivated by the amdgpu DRM driver, which needs floating-point code to support recent hardware. That code is not performance-critical, so only provide a minimal non-preemptible implementation for now. Support is limited to riscv64 because riscv32 requires runtime (libgcc) assistance to convert between doubles and 64-bit integers. Acked-by: Palmer Dabbelt <palmer@rivosinc.com> Reviewed-by: Palmer Dabbelt <palmer@rivosinc.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Samuel Holland <samuel.holland@sifive.com> Signed-off-by: Björn Töpel <bjorn@rivosinc.com>
The compiler flags enable altivec, but that is not required; hard-float is sufficient for the code to build and function. Drop altivec from the compiler flags and adjust the enable/disable code to only enable FPU use. Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Acked-by: Alex Deucher <alexander.deucher@amd.com> Signed-off-by: Samuel Holland <samuel.holland@sifive.com> Signed-off-by: Björn Töpel <bjorn@rivosinc.com>
Now that all previously-supported architectures select ARCH_HAS_KERNEL_FPU_SUPPORT, this code can depend on that symbol instead of the existing list of architectures. It can also take advantage of the common kernel-mode FPU API and method of adjusting CFLAGS. Acked-by: Alex Deucher <alexander.deucher@amd.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Samuel Holland <samuel.holland@sifive.com> Signed-off-by: Björn Töpel <bjorn@rivosinc.com>
This ensures no compiler-generated floating-point code can appear
outside kernel_fpu_{begin,end}() sections, and some architectures
enforce this separation.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Samuel Holland <samuel.holland@sifive.com>
Signed-off-by: Björn Töpel <bjorn@rivosinc.com>
Now that ARCH_HAS_KERNEL_FPU_SUPPORT provides a common way to compile and run floating-point code, this test is no longer x86-specific. Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Samuel Holland <samuel.holland@sifive.com> Signed-off-by: Björn Töpel <bjorn@rivosinc.com>
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At least one diff in series https://patchwork.kernel.org/project/linux-riscv/list/?series=839689 irrelevant now. Closing PR. |
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Pull request for series with
subject: Unified cross-architecture kernel-mode FPU API
version: 3
url: https://patchwork.kernel.org/project/linux-riscv/list/?series=839059