Make the CRC32 library export a function crc32_optimizations() which
returns flags that indicate which CRC32 functions are actually executing
optimized code at runtime.
This will be used to determine whether the crc32[c]-$arch shash
algorithms should be registered in the crypto API. btrfs could also
start using these flags instead of the hack that it currently uses where
it parses the crypto_shash_driver_name.
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20241202010844.144356-4-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
Currently the CRC32 library functions are defined as weak symbols, and
the arm64 and riscv architectures override them.
This method of arch-specific overrides has the limitation that it only
works when both the base and arch code is built-in. Also, it makes the
arch-specific code be silently not used if it is accidentally built with
lib-y instead of obj-y; unfortunately the RISC-V code does this.
This commit reorganizes the code to have explicit *_arch() functions
that are called when they are enabled, similar to how some of the crypto
library code works (e.g. chacha_crypt() calls chacha_crypt_arch()).
Make the existing kconfig choice for the CRC32 implementation also
control whether the arch-optimized implementation (if one is available)
is enabled or not. Make it enabled by default if CRC32 is also enabled.
The result is that arch-optimized CRC32 library functions will be
included automatically when appropriate, but it is now possible to
disable them. They can also now be built as a loadable module if the
CRC32 library functions happen to be used only by loadable modules, in
which case the arch and base CRC32 modules will be automatically loaded
via direct symbol dependency when appropriate.
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20241202010844.144356-3-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
Remove the leading underscores from __crc32c_le_base().
This is in preparation for adding crc32c_le_arch() and eventually
renaming __crc32c_le() to crc32c_le().
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20241202010844.144356-2-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
As suggested by the B-ext spec, the Zbc (carry-less multiplication)
instructions can be used to accelerate CRC calculations. Currently, the
crc32 is the most widely used crc function inside kernel, so this patch
focuses on the optimization of just the crc32 APIs.
Compared with the current table-lookup based optimization, Zbc based
optimization can also achieve large stride during CRC calculation loop,
meantime, it avoids the memory access latency of the table-lookup based
implementation and it reduces memory footprint.
If Zbc feature is not supported in a runtime environment, then the
table-lookup based implementation would serve as fallback via alternative
mechanism.
By inspecting the vmlinux built by gcc v12.2.0 with default optimization
level (-O2), we can see below instruction count change for each 8-byte
stride in the CRC32 loop:
rv64: crc32_be (54->31), crc32_le (54->13), __crc32c_le (54->13)
rv32: crc32_be (50->32), crc32_le (50->16), __crc32c_le (50->16)
The compile target CPU is little endian, extra effort is needed for byte
swapping for the crc32_be API, thus, the instruction count change is not
as significant as that in the *_le cases.
This patch is tested on QEMU VM with the kernel CRC32 selftest for both
rv64 and rv32. Running the CRC32 selftest on a real hardware (SpacemiT K1)
with Zbc extension shows 65% and 125% performance improvement respectively
on crc32_test() and crc32c_test().
Signed-off-by: Xiao Wang <xiao.w.wang@intel.com>
Reviewed-by: Charlie Jenkins <charlie@rivosinc.com>
Link: https://lore.kernel.org/r/20240621054707.1847548-1-xiao.w.wang@intel.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
In case they help the compiler.
Signed-off-by: George Spelvin <linux@horizon.com>
Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
There's no need for a full 32x32 matrix, when rows before the last are
just shifted copies of the rows after them.
There's still room for improvement (especially on X86 processors with
CRC32 and PCLMUL instructions), but this is a large step in the
right direction [which is in particular useful for its current user,
namely SCTP checksumming over multiple skb frags[] entries, i.e. in
IPVS balancing when other CRC32 offloads are not available].
The internal primitive is now called crc32_generic_shift and takes one
less argument; the XOR with crc2 is done in inline wrappers.
Signed-off-by: George Spelvin <linux@horizon.com>
Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This patch adds a combinator to merge two or more crc32{,c}s
into a new one. This is useful for checksum computations of
fragmented skbs that use crc32/crc32c as checksums.
The arithmetics for combining both in the GF(2) was taken and
slightly modified from zlib. Only passing two crcs is insufficient
as two crcs and the length of the second piece is needed for
merging. The code is made generic, so that only polynomials
need to be passed for crc32_le resp. crc32c_le.
Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: David S. Miller <davem@davemloft.net>
Reuse the existing crc32 code to stamp out a crc32c implementation.
Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Bob Pearson <rpearson@systemfabricworks.com>
Cc: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Add brackets around typecasted argument in crc32() macro.
Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This patch replaces bitreverse() by bitrev32. The only users of bitreverse()
are crc32 itself and via-velocity.
Cc: Jeff Garzik <jgarzik@pobox.com>
Cc: Matt Domsch <Matt_Domsch@dell.com>
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
