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Use the existing CC_FPU_CFLAGS and CC_NO_FPU_CFLAGS to pass the
appropriate compiler command line options for building kernel mode NEON
intrinsics code. This is tidier, and will make it easier to reuse the
code for 32-bit ARM.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20260330144630.33026-9-ardb@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
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Implement an optimized CRC64 (NVMe) algorithm for ARM64 using NEON
Polynomial Multiply Long (PMULL) instructions. The generic shift-and-XOR
software implementation is slow, which creates a bottleneck in NVMe and
other storage subsystems.
The acceleration is implemented using C intrinsics (<arm_neon.h>) rather
than raw assembly for better readability and maintainability.
Key highlights of this implementation:
- Uses 4KB chunking inside scoped_ksimd() to avoid preemption latency
spikes on large buffers.
- Pre-calculates and loads fold constants via vld1q_u64() to minimize
register spilling.
- Benchmarks show the break-even point against the generic implementation
is around 128 bytes. The PMULL path is enabled only for len >= 128.
Performance results (kunit crc_benchmark on Cortex-A72):
- Generic (len=4096): ~268 MB/s
- PMULL (len=4096): ~1556 MB/s (nearly 6x improvement)
Signed-off-by: Demian Shulhan <demyansh@gmail.com>
Link: https://lore.kernel.org/r/20260329074338.1053550-1-demyansh@gmail.com
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
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Move the x86-optimized CRC code from arch/x86/lib/crc* into its new
location in lib/crc/x86/, and wire it up in the new way. This new way
of organizing the CRC code eliminates the need to artificially split the
code for each CRC variant into separate arch and generic modules,
enabling better inlining and dead code elimination. For more details,
see "lib/crc: Prepare for arch-optimized code in subdirs of lib/crc/".
Reviewed-by: "Martin K. Petersen" <martin.petersen@oracle.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Acked-by: "Jason A. Donenfeld" <Jason@zx2c4.com>
Link: https://lore.kernel.org/r/20250607200454.73587-12-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
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Move the sparc-optimized CRC code from arch/sparc/lib/crc* into its new
location in lib/crc/sparc/, and wire it up in the new way. This new way
of organizing the CRC code eliminates the need to artificially split the
code for each CRC variant into separate arch and generic modules,
enabling better inlining and dead code elimination. For more details,
see "lib/crc: Prepare for arch-optimized code in subdirs of lib/crc/".
Reviewed-by: "Martin K. Petersen" <martin.petersen@oracle.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Acked-by: "Jason A. Donenfeld" <Jason@zx2c4.com>
Link: https://lore.kernel.org/r/20250607200454.73587-11-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
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Move the s390-optimized CRC code from arch/s390/lib/crc* into its new
location in lib/crc/s390/, and wire it up in the new way. This new way
of organizing the CRC code eliminates the need to artificially split the
code for each CRC variant into separate arch and generic modules,
enabling better inlining and dead code elimination. For more details,
see "lib/crc: Prepare for arch-optimized code in subdirs of lib/crc/".
Reviewed-by: "Martin K. Petersen" <martin.petersen@oracle.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Acked-by: "Jason A. Donenfeld" <Jason@zx2c4.com>
Link: https://lore.kernel.org/r/20250607200454.73587-10-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
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Move the riscv-optimized CRC code from arch/riscv/lib/crc* into its new
location in lib/crc/riscv/, and wire it up in the new way. This new way
of organizing the CRC code eliminates the need to artificially split the
code for each CRC variant into separate arch and generic modules,
enabling better inlining and dead code elimination. For more details,
see "lib/crc: Prepare for arch-optimized code in subdirs of lib/crc/".
Reviewed-by: "Martin K. Petersen" <martin.petersen@oracle.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Acked-by: "Jason A. Donenfeld" <Jason@zx2c4.com>
Link: https://lore.kernel.org/r/20250607200454.73587-9-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
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Move the powerpc-optimized CRC code from arch/powerpc/lib/crc* into its
new location in lib/crc/powerpc/, and wire it up in the new way. This
new way of organizing the CRC code eliminates the need to artificially
split the code for each CRC variant into separate arch and generic
modules, enabling better inlining and dead code elimination. For more
details, see "lib/crc: Prepare for arch-optimized code in subdirs of
lib/crc/".
Reviewed-by: "Martin K. Petersen" <martin.petersen@oracle.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Acked-by: "Jason A. Donenfeld" <Jason@zx2c4.com>
Link: https://lore.kernel.org/r/20250607200454.73587-8-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
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Move the arm64-optimized CRC code from arch/arm64/lib/crc* into its new
location in lib/crc/arm64/, and wire it up in the new way. This new way
of organizing the CRC code eliminates the need to artificially split the
code for each CRC variant into separate arch and generic modules,
enabling better inlining and dead code elimination. For more details,
see "lib/crc: Prepare for arch-optimized code in subdirs of lib/crc/".
Reviewed-by: "Martin K. Petersen" <martin.petersen@oracle.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Acked-by: "Jason A. Donenfeld" <Jason@zx2c4.com>
Link: https://lore.kernel.org/r/20250607200454.73587-5-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
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Move the arm-optimized CRC code from arch/arm/lib/crc* into its new
location in lib/crc/arm/, and wire it up in the new way. This new way
of organizing the CRC code eliminates the need to artificially split the
code for each CRC variant into separate arch and generic modules,
enabling better inlining and dead code elimination. For more details,
see "lib/crc: Prepare for arch-optimized code in subdirs of lib/crc/".
Reviewed-by: "Martin K. Petersen" <martin.petersen@oracle.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Acked-by: "Jason A. Donenfeld" <Jason@zx2c4.com>
Link: https://lore.kernel.org/r/20250607200454.73587-4-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
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Rework how lib/crc/ supports arch-optimized code. First, instead of the
arch-optimized CRC code being in arch/$(SRCARCH)/lib/, it will now be in
lib/crc/$(SRCARCH)/. Second, the API functions (e.g. crc32c()),
arch-optimized functions (e.g. crc32c_arch()), and generic functions
(e.g. crc32c_base()) will now be part of a single module for each CRC
type, allowing better inlining and dead code elimination. The second
change is made possible by the first.
As an example, consider CONFIG_CRC32=m on x86. We'll now have just
crc32.ko instead of both crc32-x86.ko and crc32.ko. The two modules
were already coupled together and always both got loaded together via
direct symbol dependency, so the separation provided no benefit.
Note: later I'd like to apply the same design to lib/crypto/ too, where
often the API functions are out-of-line so this will work even better.
In those cases, for each algorithm we currently have 3 modules all
coupled together, e.g. libsha256.ko, libsha256-generic.ko, and
sha256-x86.ko. We should have just one, inline things properly, and
rely on the compiler's dead code elimination to decide the inclusion of
the generic code instead of manually setting it via kconfig.
Having arch-specific code outside arch/ was somewhat controversial when
Zinc proposed it back in 2018. But I don't think the concerns are
warranted. It's better from a technical perspective, as it enables the
improvements mentioned above. This model is already successfully used
in other places in the kernel such as lib/raid6/. The community of each
architecture still remains free to work on the code, even if it's not in
arch/. At the time there was also a desire to put the library code in
the same files as the old-school crypto API, but that was a mistake; now
that the library is separate, that's no longer a constraint either.
Reviewed-by: "Martin K. Petersen" <martin.petersen@oracle.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Acked-by: "Jason A. Donenfeld" <Jason@zx2c4.com>
Link: https://lore.kernel.org/r/20250607200454.73587-3-ebiggers@kernel.org
Link: https://lore.kernel.org/r/20250612054514.142728-1-ebiggers@kernel.org
Link: https://lore.kernel.org/r/20250621012221.4351-1-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
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Move all CRC files in lib/ into a subdirectory lib/crc/ to keep them
from cluttering up the main lib/ directory.
Reviewed-by: "Martin K. Petersen" <martin.petersen@oracle.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Acked-by: "Jason A. Donenfeld" <Jason@zx2c4.com>
Link: https://lore.kernel.org/r/20250607200454.73587-2-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
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