diff options
author | Charlie Jenkins <charlie@rivosinc.com> | 2024-01-09 02:57:04 +0300 |
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committer | Palmer Dabbelt <palmer@rivosinc.com> | 2024-01-18 04:52:31 +0300 |
commit | e11e367e9fe57164ea609807ed27184c85263355 (patch) | |
tree | 312cbe8e5587361b9be7375b14c77f1079fb8a29 /arch | |
parent | 2ce5729fce8f62b5118f56110d16006c0e22c522 (diff) | |
download | linux-e11e367e9fe57164ea609807ed27184c85263355.tar.xz |
riscv: Add checksum header
Provide checksum algorithms that have been designed to leverage riscv
instructions such as rotate. In 64-bit, can take advantage of the larger
register to avoid some overflow checking.
Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Xiao Wang <xiao.w.wang@intel.com>
Link: https://lore.kernel.org/r/20240108-optimize_checksum-v15-3-1c50de5f2167@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Diffstat (limited to 'arch')
-rw-r--r-- | arch/riscv/include/asm/checksum.h | 82 |
1 files changed, 82 insertions, 0 deletions
diff --git a/arch/riscv/include/asm/checksum.h b/arch/riscv/include/asm/checksum.h new file mode 100644 index 000000000000..5a810126aac7 --- /dev/null +++ b/arch/riscv/include/asm/checksum.h @@ -0,0 +1,82 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * Checksum routines + * + * Copyright (C) 2023 Rivos Inc. + */ +#ifndef __ASM_RISCV_CHECKSUM_H +#define __ASM_RISCV_CHECKSUM_H + +#include <linux/in6.h> +#include <linux/uaccess.h> + +#define ip_fast_csum ip_fast_csum + +/* Define riscv versions of functions before importing asm-generic/checksum.h */ +#include <asm-generic/checksum.h> + +/** + * Quickly compute an IP checksum with the assumption that IPv4 headers will + * always be in multiples of 32-bits, and have an ihl of at least 5. + * + * @ihl: the number of 32 bit segments and must be greater than or equal to 5. + * @iph: assumed to be word aligned given that NET_IP_ALIGN is set to 2 on + * riscv, defining IP headers to be aligned. + */ +static inline __sum16 ip_fast_csum(const void *iph, unsigned int ihl) +{ + unsigned long csum = 0; + int pos = 0; + + do { + csum += ((const unsigned int *)iph)[pos]; + if (IS_ENABLED(CONFIG_32BIT)) + csum += csum < ((const unsigned int *)iph)[pos]; + } while (++pos < ihl); + + /* + * ZBB only saves three instructions on 32-bit and five on 64-bit so not + * worth checking if supported without Alternatives. + */ + if (IS_ENABLED(CONFIG_RISCV_ISA_ZBB) && + IS_ENABLED(CONFIG_RISCV_ALTERNATIVE)) { + unsigned long fold_temp; + + asm_volatile_goto(ALTERNATIVE("j %l[no_zbb]", "nop", 0, + RISCV_ISA_EXT_ZBB, 1) + : + : + : + : no_zbb); + + if (IS_ENABLED(CONFIG_32BIT)) { + asm(".option push \n\ + .option arch,+zbb \n\ + not %[fold_temp], %[csum] \n\ + rori %[csum], %[csum], 16 \n\ + sub %[csum], %[fold_temp], %[csum] \n\ + .option pop" + : [csum] "+r" (csum), [fold_temp] "=&r" (fold_temp)); + } else { + asm(".option push \n\ + .option arch,+zbb \n\ + rori %[fold_temp], %[csum], 32 \n\ + add %[csum], %[fold_temp], %[csum] \n\ + srli %[csum], %[csum], 32 \n\ + not %[fold_temp], %[csum] \n\ + roriw %[csum], %[csum], 16 \n\ + subw %[csum], %[fold_temp], %[csum] \n\ + .option pop" + : [csum] "+r" (csum), [fold_temp] "=&r" (fold_temp)); + } + return (__force __sum16)(csum >> 16); + } +no_zbb: +#ifndef CONFIG_32BIT + csum += ror64(csum, 32); + csum >>= 32; +#endif + return csum_fold((__force __wsum)csum); +} + +#endif /* __ASM_RISCV_CHECKSUM_H */ |