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[86.9.131.95]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3e177488999sm6565829f8f.36.2025.09.05.10.12.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 05 Sep 2025 10:12:22 -0700 (PDT) Date: Fri, 5 Sep 2025 18:12:21 +0100 From: Stafford Horne To: ChenMiao Cc: Linux Kernel , Linux OpenRISC , Jonathan Corbet , Jonas Bonn , Stefan Kristiansson , Peter Zijlstra , Josh Poimboeuf , Jason Baron , Steven Rostedt , Ard Biesheuvel , Masahiro Yamada , Johannes Berg , Nicolas Schier , Sahil Siddiq , linux-doc@vger.kernel.org Subject: Re: [PATCH v4 4/4] openrisc: Add jump label support Message-ID: References: <20250904100109.688033-1-chenmiao.ku@gmail.com> <20250904100109.688033-5-chenmiao.ku@gmail.com> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250904100109.688033-5-chenmiao.ku@gmail.com> On Thu, Sep 04, 2025 at 10:00:52AM +0000, ChenMiao wrote: > From: chenmiao > > Supported a complete jump_label implementation based on the ARM64 and > RV64 version and add the CONFIG_JUMP_LABEL=y to the defconfig. > > Testing was conducted using a dedicated test module (jump-label-test, > provided in the link below) with the following environment: Below is > a brief usage and test report of this module. For detailed steps, > please refer to the README in the provided link. Maybe you can shorten to: Testing was conducted using a dedicated test module jump-label-test, provided in the link below. For detailed steps, please refer to the README also at the provided link. > Link: https://github.com/ChenMiaoi/GSoC-2025-Final-Report/tree/main/tests/jump-label-test > > Test Environment: > - Hardware: QEMU emulated OR1K > - Kernel Version: 6.17.0-rc3-dirty > - Configs: CONFIG_MODULES=y,CONFIG_MODULE_UNLOAD=y > - Toolchain: or1k-none-linux-musl-gcc 15.1.0 > > Test Procedure: > 1. Build and install modules (make modules_install) > 2. Build the jump-label-test module > 3. Boot kernel in QEMU > 4. Transfer jump_label_test.ko via NFS > 5. Load module and observe results The procedure is in the readme, maybe its not needed here. > Test Results: > $ insmod jump_label_test.ko > [ 32.590000] Jump label performance test module loaded > [ 35.250000] Normal branch time: 1241327150 ns (124 ns per iteration) > [ 35.250000] Jump label (false) time: 706422700 ns (70 ns per iteration) > [ 35.250000] Jump label (true) time: 708913450 ns (70 ns per iteration) > $ rmmod jump_label_test.ko > [ 72.210000] Jump label test module unloaded > > The results show approximately 43% improvement in branch performance > when using jump labels compared to traditional branches. This is good. > Link: https://lore.kernel.org/openrisc/aK3O6kOMqgDb6zZj@antec/T/#u > Signed-off-by: chenmiao > > --- > Changes in V4: > - Add appropriate comments. > - Added testing for jump_label > > Changes in V3: > - Ensure the two defconfig using the make savedefconfig. > - modify the __ASSEMBLY__ to __ASSEMBLER__, modify the > __ASM_JUMP_LABEL_H to __ASM_OPENRISC_JUMP_LABEL_H and remove > invalid comment. > > Changes in V2: > - using the patch_insn_write(void *addr, u32 insn) not the > const void *insn. > - add new macro OPENRISC_INSN_NOP in insn-def.h to use. > > Signed-off-by: chenmiao > --- > .../core/jump-labels/arch-support.txt | 2 +- > arch/openrisc/Kconfig | 2 + > arch/openrisc/configs/or1ksim_defconfig | 1 + > arch/openrisc/configs/virt_defconfig | 1 + > arch/openrisc/include/asm/insn-def.h | 3 + > arch/openrisc/include/asm/jump_label.h | 72 +++++++++++++++++++ > arch/openrisc/kernel/Makefile | 1 + > arch/openrisc/kernel/jump_label.c | 52 ++++++++++++++ > arch/openrisc/kernel/setup.c | 2 + > 9 files changed, 135 insertions(+), 1 deletion(-) > create mode 100644 arch/openrisc/include/asm/jump_label.h > create mode 100644 arch/openrisc/kernel/jump_label.c > > diff --git a/Documentation/features/core/jump-labels/arch-support.txt b/Documentation/features/core/jump-labels/arch-support.txt > index ccada815569f..683de7c15058 100644 > --- a/Documentation/features/core/jump-labels/arch-support.txt > +++ b/Documentation/features/core/jump-labels/arch-support.txt > @@ -17,7 +17,7 @@ > | microblaze: | TODO | > | mips: | ok | > | nios2: | TODO | > - | openrisc: | TODO | > + | openrisc: | ok | > | parisc: | ok | > | powerpc: | ok | > | riscv: | ok | > diff --git a/arch/openrisc/Kconfig b/arch/openrisc/Kconfig > index b38fee299bc4..9156635dd264 100644 > --- a/arch/openrisc/Kconfig > +++ b/arch/openrisc/Kconfig > @@ -24,6 +24,8 @@ config OPENRISC > select GENERIC_PCI_IOMAP > select GENERIC_IOREMAP > select GENERIC_CPU_DEVICES > + select HAVE_ARCH_JUMP_LABEL > + select HAVE_ARCH_JUMP_LABEL_RELATIVE > select HAVE_PCI > select HAVE_UID16 > select HAVE_PAGE_SIZE_8KB > diff --git a/arch/openrisc/configs/or1ksim_defconfig b/arch/openrisc/configs/or1ksim_defconfig > index 58e27d8fdb4e..769705ac24d5 100644 > --- a/arch/openrisc/configs/or1ksim_defconfig > +++ b/arch/openrisc/configs/or1ksim_defconfig > @@ -10,6 +10,7 @@ CONFIG_EXPERT=y > # CONFIG_KALLSYMS is not set > CONFIG_BUILTIN_DTB_NAME="or1ksim" > CONFIG_HZ_100=y > +CONFIG_JUMP_LABEL=y > CONFIG_MODULES=y > # CONFIG_BLOCK is not set > CONFIG_SLUB_TINY=y > diff --git a/arch/openrisc/configs/virt_defconfig b/arch/openrisc/configs/virt_defconfig > index 8a581e932766..a93a3e1e4f87 100644 > --- a/arch/openrisc/configs/virt_defconfig > +++ b/arch/openrisc/configs/virt_defconfig > @@ -12,6 +12,7 @@ CONFIG_NR_CPUS=8 > CONFIG_SMP=y > CONFIG_HZ_100=y > # CONFIG_OPENRISC_NO_SPR_SR_DSX is not set > +CONFIG_JUMP_LABEL=y > # CONFIG_COMPAT_BRK is not set > CONFIG_NET=y > CONFIG_PACKET=y > diff --git a/arch/openrisc/include/asm/insn-def.h b/arch/openrisc/include/asm/insn-def.h > index e28a9a9604fc..1e0c028a5b95 100644 > --- a/arch/openrisc/include/asm/insn-def.h > +++ b/arch/openrisc/include/asm/insn-def.h > @@ -9,4 +9,7 @@ > /* or1k instructions are always 32 bits. */ > #define OPENRISC_INSN_SIZE 4 > > +/* or1k nop instruction code */ > +#define OPENRISC_INSN_NOP 0x15000000U > + > #endif /* __ASM_OPENRISC_INSN_DEF_H */ > diff --git a/arch/openrisc/include/asm/jump_label.h b/arch/openrisc/include/asm/jump_label.h > new file mode 100644 > index 000000000000..3ec0f4e19f9c > --- /dev/null > +++ b/arch/openrisc/include/asm/jump_label.h > @@ -0,0 +1,72 @@ > +/* SPDX-License-Identifier: GPL-2.0-only */ > +/* > + * Copyright (C) 2025 Chen Miao > + * > + * Based on arch/arm/include/asm/jump_label.h > + */ > +#ifndef __ASM_OPENRISC_JUMP_LABEL_H > +#define __ASM_OPENRISC_JUMP_LABEL_H > + > +#ifndef __ASSEMBLER__ > + > +#include > +#include > + > +#define HAVE_JUMP_LABEL_BATCH > + > +#define JUMP_LABEL_NOP_SIZE OPENRISC_INSN_SIZE > + > +/** > + * JUMP_TABLE_ENTRY - Create a jump table entry > + * @key: Jump key identifier (typically a symbol address) > + * @label: Target label address > + * > + * This macro creates a jump table entry in the dedicated kernel section (__jump_table). > + * Each entry contains the following information: > + * Offset from current instruction to jump instruction (1b - .) > + * Offset from current instruction to target label (label - .) > + * Offset from current instruction to key identifier (key - .) > + */ > +#define JUMP_TABLE_ENTRY(key, label) \ > + ".pushsection __jump_table, \"aw\" \n\t" \ > + ".align 4 \n\t" \ > + ".long 1b - ., " label " - . \n\t" \ > + ".long " key " - . \n\t" \ > + ".popsection \n\t" > + > +#define ARCH_STATIC_BRANCH_ASM(key, label) \ > + ".align 4 \n\t" \ > + "1: l.nop \n\t" \ > + " l.nop \n\t" \ > + JUMP_TABLE_ENTRY(key, label) > + > +static __always_inline bool arch_static_branch(struct static_key *const key, > + const bool branch) > +{ > + asm goto (ARCH_STATIC_BRANCH_ASM("%0", "%l[l_yes]") > + ::"i"(&((char *)key)[branch])::l_yes); > + > + return false; > +l_yes: > + return true; > +} > + > +#define ARCH_STATIC_BRANCH_JUMP_ASM(key, label) \ > + ".align 4 \n\t" \ > + "1: l.j " label " \n\t" \ > + " l.nop \n\t" \ > + JUMP_TABLE_ENTRY(key, label) > + > +static __always_inline bool > +arch_static_branch_jump(struct static_key *const key, const bool branch) > +{ > + asm goto (ARCH_STATIC_BRANCH_JUMP_ASM("%0", "%l[l_yes]") > + ::"i"(&((char *)key)[branch])::l_yes); > + > + return false; > +l_yes: > + return true; > +} > + > +#endif /* __ASSEMBLER__ */ > +#endif /* __ASM_OPENRISC_JUMP_LABEL_H */ > diff --git a/arch/openrisc/kernel/Makefile b/arch/openrisc/kernel/Makefile > index f0957ce16d6b..19e0eb94f2eb 100644 > --- a/arch/openrisc/kernel/Makefile > +++ b/arch/openrisc/kernel/Makefile > @@ -9,6 +9,7 @@ obj-y := head.o setup.o or32_ksyms.o process.o dma.o \ > traps.o time.o irq.o entry.o ptrace.o signal.o \ > sys_call_table.o unwinder.o cacheinfo.o > > +obj-$(CONFIG_JUMP_LABEL) += jump_label.o > obj-$(CONFIG_SMP) += smp.o sync-timer.o > obj-$(CONFIG_STACKTRACE) += stacktrace.o > obj-$(CONFIG_MODULES) += module.o > diff --git a/arch/openrisc/kernel/jump_label.c b/arch/openrisc/kernel/jump_label.c > new file mode 100644 > index 000000000000..071dacad885c > --- /dev/null > +++ b/arch/openrisc/kernel/jump_label.c > @@ -0,0 +1,52 @@ > +// SPDX-License-Identifier: GPL-2.0-only > +/* > + * Copyright (C) 2025 Chen Miao > + * > + * Based on arch/arm/kernel/jump_label.c > + */ > +#include > +#include > +#include > +#include > +#include > +#include > + > +bool arch_jump_label_transform_queue(struct jump_entry *entry, > + enum jump_label_type type) > +{ > + void *addr = (void *)jump_entry_code(entry); > + u32 insn; > + > + if (type == JUMP_LABEL_JMP) { > + long offset; > + > + offset = jump_entry_target(entry) - jump_entry_code(entry); > + /* > + * The actual maximum range of the l.j instruction's offset is -134,217,728 > + * ~ 134,217,724 (sign 26-bit imm). > + * For the original jump range, we need to right-shift N by 2 to obtain the > + * instruction's offset. > + */ > + if (unlikely(offset < -134217728 || offset > 134217724)) { > + WARN_ON_ONCE(true); > + } > + /* 26bit imm mask */ > + offset = (offset >> 2) & 0x03ffffff; > + > + insn = offset; > + } else { > + insn = OPENRISC_INSN_NOP; > + } > + > + if (early_boot_irqs_disabled) { > + copy_to_kernel_nofault(addr, &insn, sizeof(insn)); > + } else { > + patch_insn_write(addr, insn); > + } > + return true; > +} > + > +void arch_jump_label_transform_apply(void) > +{ > + kick_all_cpus_sync(); > +} > diff --git a/arch/openrisc/kernel/setup.c b/arch/openrisc/kernel/setup.c > index a9fb9cc6779e..000a9cc10e6f 100644 > --- a/arch/openrisc/kernel/setup.c > +++ b/arch/openrisc/kernel/setup.c > @@ -249,6 +249,8 @@ void __init setup_arch(char **cmdline_p) > initrd_below_start_ok = 1; > } > #endif > + /* perform jump_table sorting before paging_init locks down read only memory */ > + jump_label_init(); > > /* paging_init() sets up the MMU and marks all pages as reserved */ > paging_init(); > -- > 2.45.2 >