From 1c7d491d8678ee056ee91de5cb14c9afa50175cb Mon Sep 17 00:00:00 2001 From: Vivian Wang Date: Mon, 17 Nov 2025 21:19:21 -0700 Subject: [PATCH] riscv: checksum: Use riscv_has_extension_likely Use riscv_has_extension_likely() to check for RISCV_ISA_EXT_ZBB, replacing the use of asm goto with ALTERNATIVE. The "likely" variant is used to match the behavior of the original implementation using ALTERNATIVE("j %l[no_zbb]", "nop", ...). While we're at it, also remove bogus comment about Zbb being likely available. We have to choose between "likely" and "unlikely" due to limitations of the asm goto feature, but that does not mean we should put a bad comment on why we pick "likely" over "unlikely". Signed-off-by: Vivian Wang Link: https://patch.msgid.link/20251020-riscv-altn-helper-wip-v4-2-ef941c87669a@iscas.ac.cn Signed-off-by: Paul Walmsley --- arch/riscv/include/asm/checksum.h | 13 +++----- arch/riscv/lib/csum.c | 53 +++++++------------------------ 2 files changed, 16 insertions(+), 50 deletions(-) diff --git a/arch/riscv/include/asm/checksum.h b/arch/riscv/include/asm/checksum.h index da378856f1d59..945cce34be921 100644 --- a/arch/riscv/include/asm/checksum.h +++ b/arch/riscv/include/asm/checksum.h @@ -49,16 +49,11 @@ static inline __sum16 ip_fast_csum(const void *iph, unsigned int 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_TOOLCHAIN_HAS_ZBB)) { + if (IS_ENABLED(CONFIG_RISCV_ISA_ZBB) && + IS_ENABLED(CONFIG_TOOLCHAIN_HAS_ZBB) && + riscv_has_extension_likely(RISCV_ISA_EXT_ZBB)) { unsigned long fold_temp; - asm 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\ @@ -81,7 +76,7 @@ static inline __sum16 ip_fast_csum(const void *iph, unsigned int ihl) } return (__force __sum16)(csum >> 16); } -no_zbb: + #ifndef CONFIG_32BIT csum += ror64(csum, 32); csum >>= 32; diff --git a/arch/riscv/lib/csum.c b/arch/riscv/lib/csum.c index 9408f50ca59a8..75bd0abffd631 100644 --- a/arch/riscv/lib/csum.c +++ b/arch/riscv/lib/csum.c @@ -40,20 +40,11 @@ __sum16 csum_ipv6_magic(const struct in6_addr *saddr, uproto = (__force unsigned int)htonl(proto); sum += uproto; - if (IS_ENABLED(CONFIG_RISCV_ISA_ZBB) && IS_ENABLED(CONFIG_TOOLCHAIN_HAS_ZBB)) { + if (IS_ENABLED(CONFIG_RISCV_ISA_ZBB) && + IS_ENABLED(CONFIG_TOOLCHAIN_HAS_ZBB) && + riscv_has_extension_likely(RISCV_ISA_EXT_ZBB)) { unsigned long fold_temp; - /* - * Zbb is likely available when the kernel is compiled with Zbb - * support, so nop when Zbb is available and jump when Zbb is - * not available. - */ - asm goto(ALTERNATIVE("j %l[no_zbb]", "nop", 0, - RISCV_ISA_EXT_ZBB, 1) - : - : - : - : no_zbb); asm(".option push \n\ .option arch,+zbb \n\ rori %[fold_temp], %[sum], 32 \n\ @@ -66,7 +57,7 @@ __sum16 csum_ipv6_magic(const struct in6_addr *saddr, : [sum] "+r" (sum), [fold_temp] "=&r" (fold_temp)); return (__force __sum16)(sum >> 16); } -no_zbb: + sum += ror64(sum, 32); sum >>= 32; return csum_fold((__force __wsum)sum); @@ -152,21 +143,11 @@ do_csum_with_alignment(const unsigned char *buff, int len) csum = do_csum_common(ptr, end, data); #ifdef CC_HAS_ASM_GOTO_TIED_OUTPUT - if (IS_ENABLED(CONFIG_RISCV_ISA_ZBB) && IS_ENABLED(CONFIG_TOOLCHAIN_HAS_ZBB)) { + if (IS_ENABLED(CONFIG_RISCV_ISA_ZBB) && + IS_ENABLED(CONFIG_TOOLCHAIN_HAS_ZBB) && + riscv_has_extension_likely(RISCV_ISA_EXT_ZBB)) { unsigned long fold_temp; - /* - * Zbb is likely available when the kernel is compiled with Zbb - * support, so nop when Zbb is available and jump when Zbb is - * not available. - */ - asm goto(ALTERNATIVE("j %l[no_zbb]", "nop", 0, - RISCV_ISA_EXT_ZBB, 1) - : - : - : - : no_zbb); - #ifdef CONFIG_32BIT asm_goto_output(".option push \n\ .option arch,+zbb \n\ @@ -204,7 +185,7 @@ do_csum_with_alignment(const unsigned char *buff, int len) end: return csum >> 16; } -no_zbb: + #endif /* CC_HAS_ASM_GOTO_TIED_OUTPUT */ #ifndef CONFIG_32BIT csum += ror64(csum, 32); @@ -234,21 +215,11 @@ do_csum_no_alignment(const unsigned char *buff, int len) end = (const unsigned long *)(buff + len); csum = do_csum_common(ptr, end, data); - if (IS_ENABLED(CONFIG_RISCV_ISA_ZBB) && IS_ENABLED(CONFIG_TOOLCHAIN_HAS_ZBB)) { + if (IS_ENABLED(CONFIG_RISCV_ISA_ZBB) && + IS_ENABLED(CONFIG_TOOLCHAIN_HAS_ZBB) && + riscv_has_extension_likely(RISCV_ISA_EXT_ZBB)) { unsigned long fold_temp; - /* - * Zbb is likely available when the kernel is compiled with Zbb - * support, so nop when Zbb is available and jump when Zbb is - * not available. - */ - asm goto(ALTERNATIVE("j %l[no_zbb]", "nop", 0, - RISCV_ISA_EXT_ZBB, 1) - : - : - : - : no_zbb); - #ifdef CONFIG_32BIT asm (".option push \n\ .option arch,+zbb \n\ @@ -274,7 +245,7 @@ do_csum_no_alignment(const unsigned char *buff, int len) #endif /* !CONFIG_32BIT */ return csum >> 16; } -no_zbb: + #ifndef CONFIG_32BIT csum += ror64(csum, 32); csum >>= 32; -- 2.47.3