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Thu, 30 Jan 2025 17:26:23 -0800 (PST) Received: from charlie.ba.rivosinc.com ([64.71.180.162]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-2f83bf95b44sm4691047a91.37.2025.01.30.17.26.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 30 Jan 2025 17:26:22 -0800 (PST) From: Charlie Jenkins Date: Thu, 30 Jan 2025 17:26:12 -0800 Subject: [PATCH v4] riscv: Add runtime constant support MIME-Version: 1.0 Message-Id: <20250130-runtime_const_riscv-v4-1-2d36c41b7b9c@rivosinc.com> X-B4-Tracking: v=1; b=H4sIALMmnGcC/43N0QqCMBTG8VeRXbdwZ9pcV71HhOg85rloi81GI b57UwgivOjy/8H5nYkF9ISBHbOJeYwUyNkUxS5jZmjsFTl1qRnkUOYCJPcPO9INa+NsGGtPwUR +MF1VFohQCcXS5d1jT89VPV9SDxRG51/rkyiW9eOpTS8KLrjSZZuDxAby9uQpukDW7I27sYWM8 AcDidFlg8r0WjVSbzDym6m2GZkYITSArjRCJ3+YeZ7fW9YFsUcBAAA= X-Change-ID: 20250123-runtime_const_riscv-6cd854ee2817 To: Paul Walmsley , Palmer Dabbelt , Ard Biesheuvel , Ben Dooks , Pasha Bouzarjomehri , Emil Renner Berthing Cc: linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, Charlie Jenkins X-Mailer: b4 0.14.2 X-Developer-Signature: v=1; a=openpgp-sha256; l=8307; i=charlie@rivosinc.com; h=from:subject:message-id; bh=fRVAyJRZWPS7vdG0um+ImMkb5g/yW1KIBkWdtJLFg14=; b=owGbwMvMwCXWx5hUnlvL8Y3xtFoSQ/octR2nHlY2LpQ+5HrsF9vUTPG+j3KGc7NubukM+vTo1 Pri6VYMHaUsDGJcDLJiiiw81xqYW+/olx0VLZsAM4eVCWQIAxenAExkvQnD/0Kdg7vF/m+WaKze 4bhNiuuLkuOGCZ/qP3rIHnyieDhWy5KRYfkKiWSxYxudD53rXhDdpsP+qmPnn/Rrpb/KPxW8Ki/ dxQ4A X-Developer-Key: i=charlie@rivosinc.com; a=openpgp; fpr=7D834FF11B1D8387E61C776FFB10D1F27D6B1354 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250130_172624_883258_78976696 X-CRM114-Status: GOOD ( 19.06 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org Implement the runtime constant infrastructure for riscv. Use this infrastructure to generate constants to be used by the d_hash() function. This is the riscv variant of commit 94a2bc0f611c ("arm64: add 'runtime constant' support") and commit e3c92e81711d ("runtime constants: add x86 architecture support"). Signed-off-by: Charlie Jenkins --- Ard brought this to my attention in this patch [1]. [1] https://lore.kernel.org/lkml/CAMj1kXE4DJnwFejNWQu784GvyJO=aGNrzuLjSxiowX_e7nW8QA@mail.gmail.com/ --- Changes in v4: - Add newlines after riscv32 assembler directives - Align instructions along 32-bit boundary (Emil) - Link to v3: https://lore.kernel.org/r/20250128-runtime_const_riscv-v3-1-11922989e2d3@rivosinc.com Changes in v3: - Leverage "pack" instruction for runtime_const_ptr() to reduce hot path by 3 instructions if Zbkb is supported. Suggested by Pasha Bouzarjomehri (pasha@rivosinc.com) - Link to v2: https://lore.kernel.org/r/20250127-runtime_const_riscv-v2-1-95ae7cf97a39@rivosinc.com Changes in v2: - Treat instructions as __le32 and do proper conversions (Ben) - Link to v1: https://lore.kernel.org/r/20250127-runtime_const_riscv-v1-1-795b023ea20b@rivosinc.com --- arch/riscv/include/asm/runtime-const.h | 197 +++++++++++++++++++++++++++++++++ arch/riscv/kernel/vmlinux.lds.S | 3 + 2 files changed, 200 insertions(+) --- base-commit: ffd294d346d185b70e28b1a28abe367bbfe53c04 change-id: 20250123-runtime_const_riscv-6cd854ee2817 diff --git a/arch/riscv/include/asm/runtime-const.h b/arch/riscv/include/asm/runtime-const.h new file mode 100644 index 0000000000000000000000000000000000000000..8ae288c4bfaf9b7e9c3c82b37ef820cebf8af07d --- /dev/null +++ b/arch/riscv/include/asm/runtime-const.h @@ -0,0 +1,197 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _ASM_RISCV_RUNTIME_CONST_H +#define _ASM_RISCV_RUNTIME_CONST_H + +#include +#include +#include +#include + +#ifdef CONFIG_32BIT +#define runtime_const_ptr(sym) \ +({ \ + typeof(sym) __ret, __tmp; \ + asm_inline(".align 4\n\t" \ + ".option push\n\t" \ + ".option norvc\n\t" \ + "1:\t" \ + "lui %[__ret],0x89abd\n\t" \ + "addi %[__ret],-0x211\n\t" \ + ".option pop\n\t" \ + ".pushsection runtime_ptr_" #sym ",\"a\"\n\t" \ + ".long 1b - .\n\t" \ + ".popsection" \ + : [__ret] "=r" (__ret)); \ + __ret; \ +}) +#else +/* + * Loading 64-bit constants into a register from immediates is a non-trivial + * task on riscv64. To get it somewhat performant, load 32 bits into two + * different registers and then combine the results. + * + * If the processor supports the Zbkb extension, we can combine the final + * "slli,slli,srli,add" into the single "pack" instruction. If the processor + * doesn't support Zbkb but does support the Zbb extension, we can + * combine the final "slli,srli,add" into one instruction "add.uw". + */ +#define runtime_const_ptr(sym) \ +({ \ + typeof(sym) __ret, __tmp; \ + asm_inline(".align 4\n\t" \ + ".option push\n\t" \ + ".option norvc\n\t" \ + "1:\t" \ + "lui %[__ret],0x89abd\n\t" \ + "lui %[__tmp],0x1234\n\t" \ + "addiw %[__ret],%[__ret],-0x211\n\t" \ + "addiw %[__tmp],%[__tmp],0x567\n\t" \ + ALTERNATIVE_2( \ + "slli %[__tmp],%[__tmp],32\n\t" \ + "slli %[__ret],%[__ret],32\n\t" \ + "srli %[__ret],%[__ret],32\n\t" \ + "add %[__ret],%[__ret],%[__tmp]\n\t", \ + ".option push\n\t" \ + ".option arch,+zba\n\t" \ + "slli %[__tmp],%[__tmp],32\n\t" \ + "add.uw %[__ret],%[__ret],%[__tmp]\n\t" \ + "nop\n\t" \ + "nop\n\t" \ + ".option pop\n\t", \ + 0, RISCV_ISA_EXT_ZBA, 1, \ + ".option push\n\t" \ + ".option arch,+zbkb\n\t" \ + "pack %[__ret],%[__ret],%[__tmp]\n\t" \ + "nop\n\t" \ + "nop\n\t" \ + "nop\n\t" \ + ".option pop\n\t", \ + 0, RISCV_ISA_EXT_ZBKB, 1 \ + ) \ + ".option pop\n\t" \ + ".pushsection runtime_ptr_" #sym ",\"a\"\n\t" \ + ".long 1b - .\n\t" \ + ".popsection" \ + : [__ret] "=r" (__ret), [__tmp] "=r" (__tmp)); \ + __ret; \ +}) +#endif + +#ifdef CONFIG_32BIT +#define SRLI "srli " +#else +#define SRLI "srliw " +#endif + +#define runtime_const_shift_right_32(val, sym) \ +({ \ + u32 __ret; \ + asm_inline(".align 4\n\t" \ + ".option push\n\t" \ + ".option norvc\n\t" \ + "1:\t" \ + SRLI "%[__ret],%[__val],12\n\t" \ + ".option pop\n\t" \ + ".pushsection runtime_shift_" #sym ",\"a\"\n\t" \ + ".long 1b - .\n\t" \ + ".popsection" \ + : [__ret] "=r" (__ret) \ + : [__val] "r" (val)); \ + __ret; \ +}) + +#define runtime_const_init(type, sym) do { \ + extern s32 __start_runtime_##type##_##sym[]; \ + extern s32 __stop_runtime_##type##_##sym[]; \ + \ + runtime_const_fixup(__runtime_fixup_##type, \ + (unsigned long)(sym), \ + __start_runtime_##type##_##sym, \ + __stop_runtime_##type##_##sym); \ +} while (0) + +static inline void __runtime_fixup_caches(void *where, unsigned int insns) +{ + /* On riscv there are currently only cache-wide flushes so va is ignored. */ + __always_unused uintptr_t va = (uintptr_t)where; + + flush_icache_range(va, va + 4*insns); +} + +/* + * The 32-bit immediate is stored in a lui+addi pairing. + * lui holds the upper 20 bits of the immediate in the first 20 bits of the instruction. + * addi holds the lower 12 bits of the immediate in the first 12 bits of the instruction. + */ +static inline void __runtime_fixup_32(u32 *lui, u32 *addi, unsigned int val) +{ + unsigned int lower_immediate, upper_immediate; + u32 lui_insn = le32_to_cpu(*lui); + u32 addi_insn = le32_to_cpu(*addi); + __le32 addi_res, lui_res; + + lower_immediate = sign_extend32(val, 11); + upper_immediate = (val - lower_immediate); + + if (upper_immediate & 0xfffff000) { + /* replace upper 20 bits of lui with upper immediate */ + lui_insn &= 0x00000fff; + lui_insn |= upper_immediate & 0xfffff000; + } else { + /* replace lui with nop if immediate is small enough to fit in addi */ + lui_insn = 0x00000013; + } + + if (lower_immediate & 0x00000fff) { + /* replace upper 12 bits of addi with lower 12 bits of val */ + addi_insn &= 0x000fffff; + addi_insn |= (lower_immediate & 0x00000fff) << 20; + } else { + /* replace addi with nop if lower_immediate is empty */ + addi_insn = 0x00000013; + } + + addi_res = cpu_to_le32(addi_insn); + lui_res = cpu_to_le32(lui_insn); + patch_insn_write(addi, &addi_res, sizeof(addi_res)); + patch_insn_write(lui, &lui_res, sizeof(lui_res)); +} + +static inline void __runtime_fixup_ptr(void *where, unsigned long val) +{ + if (IS_ENABLED(CONFIG_32BIT)) { + __runtime_fixup_32(where, where + 4, val); + __runtime_fixup_caches(where, 2); + } else { + __runtime_fixup_32(where, where + 8, val); + __runtime_fixup_32(where + 4, where + 12, val >> 32); + __runtime_fixup_caches(where, 4); + } +} + +/* + * Replace the least significant 5 bits of the srli/srliw immediate that is + * located at bits 20-24 + */ +static inline void __runtime_fixup_shift(void *where, unsigned long val) +{ + u32 insn = le32_to_cpu(*(__le32 *)where); + __le32 res; + + insn &= 0xfe0fffff; + insn |= (val & 0b11111) << 20; + + res = cpu_to_le32(insn); + patch_text_nosync(where, &res, sizeof(insn)); +} + +static inline void runtime_const_fixup(void (*fn)(void *, unsigned long), + unsigned long val, s32 *start, s32 *end) +{ + while (start < end) { + fn(*start + (void *)start, val); + start++; + } +} + +#endif /* _ASM_RISCV_RUNTIME_CONST_H */ diff --git a/arch/riscv/kernel/vmlinux.lds.S b/arch/riscv/kernel/vmlinux.lds.S index 002ca58dd998cb78b662837b5ebac988fb6c77bb..61bd5ba6680a786bf1db7dc37bf1acda0639b5c7 100644 --- a/arch/riscv/kernel/vmlinux.lds.S +++ b/arch/riscv/kernel/vmlinux.lds.S @@ -97,6 +97,9 @@ SECTIONS { EXIT_DATA } + + RUNTIME_CONST_VARIABLES + PERCPU_SECTION(L1_CACHE_BYTES) .rel.dyn : {