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NEON intrinsics are useful because they remove the need for manual
register allocation, and the resulting code can be re-compiled and
optimized for different micro-architectures, and shared between arm64
and 32-bit ARM.
However, the strong typing of the vector variables can lead to
incomprehensible gibberish, as is the case with the new CRC64
implementation. To address this, let's repaint all variables as
uint64x2_t to minimize the number of vreinterpretq_xxx() calls, and to
be able to rely on the ^ operator for exclusive OR operations. This
makes the code much more concise and readable.
While at it, wrap the calls to vmull_p64() et al in order to have a more
consistent calling convention, and encapsulate any remaining
vreinterpret() calls that are still needed.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20260330144630.33026-11-ardb@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
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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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On arm64, kernel mode NEON executes with preemption enabled, so there is
no need to chunk the input by hand.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20260330144630.33026-8-ardb@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
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Since support for big-endian arm64 kernels was removed, the CPU_LE()
macro now unconditionally emits the code it is passed, and the CPU_BE()
macro now unconditionally discards the code it is passed.
Simplify the assembly code in lib/crc/arm64/ accordingly.
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20260401004431.151432-1-ebiggers@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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CONFIG_KERNEL_MODE_NEON is always enabled on arm64, and it always has
been since its introduction in 2013. Given that and the fact that the
usefulness of kernel-mode NEON has only been increasing over time,
checking for this option in arm64-specific code is unnecessary. Remove
this check from lib/crc/ to simplify the code and prevent any future
bugs where e.g. code gets disabled due to a typo in this logic.
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20260314175744.30620-1-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
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Add a .kunitconfig file to the lib/crc/ directory so that the CRC
library tests can be run more easily using kunit.py. Example with UML:
tools/testing/kunit/kunit.py run --kunitconfig=lib/crc
Example with QEMU:
tools/testing/kunit/kunit.py run --kunitconfig=lib/crc --arch=arm64 --make_options LLVM=1
Link: https://lore.kernel.org/r/20260306033557.250499-4-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
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Now that crc_kunit uses the standard "depends on" pattern, enabling the
full set of CRC tests is a bit difficult, mainly due to CRC7 being
rarely used. Add a kconfig option to make it easier. It is visible
only when KUNIT, so hopefully the extra prompt won't be too annoying.
Link: https://lore.kernel.org/r/20260306033557.250499-3-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
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Like commit 4478e8eeb871 ("lib/crypto: tests: Depend on library options
rather than selecting them") did with the crypto library tests, make
crc_kunit depend on the code it tests rather than selecting it. This
follows the standard convention for KUnit and fixes an issue where
enabling KUNIT_ALL_TESTS enabled non-test code.
crc_kunit does differ from the crypto library tests in that it
consolidates the tests for multiple CRC variants, with 5 kconfig
options, into one KUnit suite. Since depending on *all* of these
kconfig options would greatly restrict the ability to enable crc_kunit,
instead just depend on *any* of these options. Update crc_kunit
accordingly to test only the reachable code.
Alternatively we could split crc_kunit into 5 test suites. But keeping
it as one is simpler for now.
Fixes: e47d9b1a76ed ("lib/crc_kunit.c: add KUnit test suite for CRC library functions")
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20260306033557.250499-2-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
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Before modifying the prototypes of kernel_neon_begin() and
kernel_neon_end() to accommodate kernel mode FP/SIMD state buffers
allocated on the stack, move arm64 to the new 'ksimd' scoped guard API,
which encapsulates the calls to those functions.
For symmetry, do the same for 32-bit ARM too.
Reviewed-by: Eric Biggers <ebiggers@kernel.org>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
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Drop 'inline' from all the *_mod_init_arch() functions so that the
compiler will warn about any bugs where they are unused due to not being
wired up properly. (There are no such bugs currently, so this just
establishes a more robust convention for the future. Of course, these
functions also tend to get inlined anyway, regardless of the keyword.)
Link: https://lore.kernel.org/r/20250816020240.431545-1-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
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Since crc_kunit now tests the fallback code paths without using
crypto_simd_disabled_for_test, make the CRC code just use the underlying
may_use_simd() and irq_fpu_usable() functions directly instead of
crypto_simd_usable(). This eliminates an unnecessary layer.
Take the opportunity to add likely() and unlikely() annotations as well.
Link: https://lore.kernel.org/r/20250811182631.376302-4-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
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Test that if CRCs are computed in task, softirq, and hardirq context
concurrently, then all results are as expected. Implement this using
kunit_run_irq_test() which is also used by the lib/crypto/ tests.
As with the corresponding lib/crypto/ tests, the purpose of this is to
test fallback code paths and to exercise edge cases in the
architecture's support for in-kernel FPU/SIMD/vector.
Remove the code from crc_test() that sometimes disabled interrupts, as
that was just an incomplete attempt to achieve similar test coverage.
Link: https://lore.kernel.org/r/20250811182631.376302-3-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
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Improve crc32c() performance on lengths >= 512 bytes by using
crc32_lsb_vpclmul_avx512() instead of crc32c_x86_3way(), when the CPU
supports VPCLMULQDQ and has a "good" implementation of AVX-512. For now
that means AMD Zen 4 and later, and Intel Sapphire Rapids and later.
Pass crc32_lsb_vpclmul_avx512() the table of constants needed to make it
use the CRC-32C polynomial.
Rationale: VPCLMULQDQ performance has improved on newer CPUs, making
crc32_lsb_vpclmul_avx512() faster than crc32c_x86_3way(), even though
crc32_lsb_vpclmul_avx512() is designed for generic 32-bit CRCs and does
not utilize x86_64's dedicated CRC-32C instructions.
Performance results for len=4096 using crc_kunit:
CPU Before (MB/s) After (MB/s)
====================== ============= ============
AMD Zen 4 (Genoa) 19868 28618
AMD Zen 5 (Ryzen AI 9 365) 24080 46940
AMD Zen 5 (Turin) 29566 58468
Intel Sapphire Rapids 22340 73794
Intel Emerald Rapids 24696 78666
Performance results for len=512 using crc_kunit:
CPU Before (MB/s) After (MB/s)
====================== ============= ============
AMD Zen 4 (Genoa) 7251 7758
AMD Zen 5 (Ryzen AI 9 365) 17481 19135
AMD Zen 5 (Turin) 21332 25424
Intel Sapphire Rapids 18886 29312
Intel Emerald Rapids 19675 29045
That being said, in the above benchmarks the ZMM registers are "warm",
so they don't quite tell the whole story. While significantly improved
from older Intel CPUs, Intel still has ~2000 ns of ZMM warm-up time
where 512-bit instructions execute 4 times more slowly than they
normally do. In contrast, AMD does better and has virtually zero ZMM
warm-up time (at most ~60 ns). Thus, while this change is always
beneficial on AMD, strictly speaking there are cases in which it is not
beneficial on Intel, e.g. a small number of 512-byte messages with
"cold" ZMM registers. But typically, it is beneficial even on Intel.
Note that on AMD Zen 3--5, crc32c() performance could be further
improved with implementations that interleave crc32q and VPCLMULQDQ
instructions. Unfortunately, it appears that a different such
implementation would be optimal on *each* of these microarchitectures.
Such improvements are left for future work. This commit just improves
the way that we choose the implementations we already have.
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20250719224938.126512-3-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
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Reorganize the crc-pclmul static_call initialization to place more of
the logic in the *_mod_init_arch() functions instead of in the
INIT_CRC_PCLMUL macro. This provides the flexibility to do more than a
single static_call update for each CPU feature check. Right away,
optimize crc64_mod_init_arch() to check the CPU features just once
instead of twice, doing both the crc64_msb and crc64_lsb static_call
updates together. A later commit will also use this to initialize an
additional static_key when crc32_lsb_vpclmul_avx512() is enabled.
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20250719224938.126512-2-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
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Fix build warnings with W=1 that started appearing after
commit a934a57a42f6 ("scripts/misc-check: check missing #include
<linux/export.h> when W=1"). While at it, sort the include lists
alphabetically.
Link: https://lore.kernel.org/r/20250612183852.114878-1-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
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These symbols are no longer used, so remove them.
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/20250607200454.73587-13-ebiggers@kernel.org
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 mips-optimized CRC code from arch/mips/lib/crc* into its new
location in lib/crc/mips/, 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/20250607200454.73587-7-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
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Move the loongarch-optimized CRC code from arch/loongarch/lib/crc* into
its new location in lib/crc/loongarch/, 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/20250607200454.73587-6-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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