Messages in this thread Patch in this message | | | From | Clément Léger <> | Subject | [RFC V2 PATCH 9/9] riscv: add floating point insn support to misaligned access emulation | Date | Tue, 4 Jul 2023 16:09:24 +0200 |
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This support is partially based of openSBI misaligned emulation floating point instruction support. It provides support for the existing floating point instructions (both for 32/64 bits as well as compressed ones). Since floating point registers are not part of the pt_regs struct, we need to modify them directly using some assembly. We also dirty the pt_regs status in case we modify them to be sure context switch will save FP state. With this support, Linux is on par with openSBI support.
Signed-off-by: Clément Léger <cleger@rivosinc.com> --- arch/riscv/kernel/fpu.S | 117 +++++++++++++++++++++ arch/riscv/kernel/traps_misaligned.c | 152 ++++++++++++++++++++++++++- 2 files changed, 265 insertions(+), 4 deletions(-)
diff --git a/arch/riscv/kernel/fpu.S b/arch/riscv/kernel/fpu.S index dd2205473de7..2785badb247c 100644 --- a/arch/riscv/kernel/fpu.S +++ b/arch/riscv/kernel/fpu.S @@ -104,3 +104,120 @@ ENTRY(__fstate_restore) csrc CSR_STATUS, t1 ret ENDPROC(__fstate_restore) + +#define get_f32(which) fmv.x.s a0, which; j 2f +#define put_f32(which) fmv.s.x which, a1; j 2f +#if __riscv_xlen == 64 +# define get_f64(which) fmv.x.d a0, which; j 2f +# define put_f64(which) fmv.d.x which, a1; j 2f +#else +# define get_f64(which) fsd which, 0(a1); j 2f +# define put_f64(which) fld which, 0(a1); j 2f +#endif + +.macro fp_access_prologue + /* + * Compute jump offset to store the correct FP register since we don't + * have indirect FP register access + */ + sll t0, a0, 3 + la t2, 1f + add t0, t0, t2 + li t1, SR_FS + csrs CSR_STATUS, t1 + jr t0 +1: +.endm + +.macro fp_access_epilogue +2: + csrc CSR_STATUS, t1 + ret +.endm + +#define fp_access_body(__access_func) \ + __access_func(f0); \ + __access_func(f1); \ + __access_func(f2); \ + __access_func(f3); \ + __access_func(f4); \ + __access_func(f5); \ + __access_func(f6); \ + __access_func(f7); \ + __access_func(f8); \ + __access_func(f9); \ + __access_func(f10); \ + __access_func(f11); \ + __access_func(f12); \ + __access_func(f13); \ + __access_func(f14); \ + __access_func(f15); \ + __access_func(f16); \ + __access_func(f17); \ + __access_func(f18); \ + __access_func(f19); \ + __access_func(f20); \ + __access_func(f21); \ + __access_func(f22); \ + __access_func(f23); \ + __access_func(f24); \ + __access_func(f25); \ + __access_func(f26); \ + __access_func(f27); \ + __access_func(f28); \ + __access_func(f29); \ + __access_func(f30); \ + __access_func(f31) + + +/* + * Disable compressed instructions set to keep a constant offset between FP + * load/store/move instructions + */ +.option norvc +/* + * put_f32_reg - Set a FP register from a register containing the value + * a0 = FP register index to be set + * a1 = value to be loaded in the FP register + */ +SYM_FUNC_START(put_f32_reg) + fp_access_prologue + fp_access_body(put_f32) + fp_access_epilogue +SYM_FUNC_END(put_f32_reg) + +/* + * get_f32_reg - Get a FP register value and return it + * a0 = FP register index to be retrieved + */ +SYM_FUNC_START(get_f32_reg) + fp_access_prologue + fp_access_body(get_f32) + fp_access_epilogue +SYM_FUNC_END(put_f32_reg) + +/* + * put_f64_reg - Set a 64 bits FP register from a value or a pointer. + * a0 = FP register index to be set + * a1 = value/pointer to be loaded in the FP register (when xlen == 32 bits, we + * load the value to a pointer). + */ +SYM_FUNC_START(put_f64_reg) + fp_access_prologue + fp_access_body(put_f64) + fp_access_epilogue +SYM_FUNC_END(put_f64_reg) + +/* + * put_f64_reg - Get a 64 bits FP register value and returned it or store it to + * a pointer. + * a0 = FP register index to be retrieved + * a1 = If xlen == 32, pointer which should be loaded with the FP register value + * or unused if xlen == 64. In which case the FP register value is returned + * through a0 + */ +SYM_FUNC_START(get_f64_reg) + fp_access_prologue + fp_access_body(get_f64) + fp_access_epilogue +SYM_FUNC_END(get_f64_reg) diff --git a/arch/riscv/kernel/traps_misaligned.c b/arch/riscv/kernel/traps_misaligned.c index 5fb6758b0bf9..c4c4672a4554 100644 --- a/arch/riscv/kernel/traps_misaligned.c +++ b/arch/riscv/kernel/traps_misaligned.c @@ -156,6 +156,115 @@ #define PRECISION_S 0 #define PRECISION_D 1 +#ifdef CONFIG_FPU + +#define FP_GET_RD(insn) (insn >> 7 & 0x1F) + +extern void put_f32_reg(unsigned long fp_reg, unsigned long value); + +static int set_f32_rd(unsigned long insn, struct pt_regs *regs, + unsigned long val) +{ + unsigned long fp_reg = FP_GET_RD(insn); + + put_f32_reg(fp_reg, val); + regs->status |= SR_FS_DIRTY; + + return 0; +} + +extern void put_f64_reg(unsigned long fp_reg, unsigned long value); + +static int set_f64_rd(unsigned long insn, struct pt_regs *regs, u64 val) +{ + unsigned long fp_reg = FP_GET_RD(insn); + unsigned long value; + +#if __riscv_xlen == 32 + value = (unsigned long) &val; +#else + value = val; +#endif + put_f64_reg(fp_reg, value); + regs->status |= SR_FS_DIRTY; + + return 0; +} + +#if __riscv_xlen == 32 +extern void get_f64_reg(unsigned long fp_reg, u64 *value); + +static u64 get_f64_rs(unsigned long insn, u8 fp_reg_offset, + struct pt_regs *regs) +{ + unsigned long fp_reg = (insn >> fp_reg_offset) & 0x1F; + u64 val; + + get_f64_reg(fp_reg, &val); + regs->status |= SR_FS_DIRTY; + + return val; +} +#else + +extern unsigned long get_f64_reg(unsigned long fp_reg); + +static unsigned long get_f64_rs(unsigned long insn, u8 fp_reg_offset, + struct pt_regs *regs) +{ + unsigned long fp_reg = (insn >> fp_reg_offset) & 0x1F; + unsigned long val; + + val = get_f64_reg(fp_reg); + regs->status |= SR_FS_DIRTY; + + return val; +} + +#endif + +extern unsigned long get_f32_reg(unsigned long fp_reg); + +static unsigned long get_f32_rs(unsigned long insn, u8 fp_reg_offset, + struct pt_regs *regs) +{ + unsigned long fp_reg = (insn >> fp_reg_offset) & 0x1F; + unsigned long val; + + val = get_f32_reg(fp_reg); + regs->status |= SR_FS_DIRTY; + + return val; +} + +#else /* CONFIG_FPU */ +static void set_f32_rd(unsigned long insn, struct pt_regs *regs, + unsigned long val) {} + +static void set_f64_rd(unsigned long insn, struct pt_regs *regs, u64 val) {} + +static unsigned long get_f64_rs(unsigned long insn, u8 fp_reg_offset, + struct pt_regs *regs) +{ + return 0; +} + +static unsigned long get_f32_rs(unsigned long insn, u8 fp_reg_offset, + struct pt_regs *regs) +{ + return 0; +} + +#endif + +#define GET_F64_RS2(insn, regs) (get_f64_rs(insn, 20, regs)) +#define GET_F64_RS2C(insn, regs) (get_f64_rs(insn, 2, regs)) +#define GET_F64_RS2S(insn, regs) (get_f64_rs(RVC_RS2S(insn), 0, regs)) + +#define GET_F32_RS2(insn, regs) (get_f32_rs(insn, 20, regs)) +#define GET_F32_RS2C(insn, regs) (get_f32_rs(insn, 2, regs)) +#define GET_F32_RS2S(insn, regs) (get_f32_rs(RVC_RS2S(insn), 0, regs)) + #ifdef CONFIG_RISCV_M_MODE static inline int load_u8(struct pt_regs *regs, const u8 *addr, u8 *r_val) { @@ -374,15 +483,21 @@ int handle_misaligned_load(struct pt_regs *regs) return -1; } + if (!IS_ENABLED(CONFIG_FPU) && fp) + return -EOPNOTSUPP; + val.data_u64 = 0; for (i = 0; i < len; i++) { if (load_u8(regs, (void *)(addr + i), &val.data_bytes[i])) return -1; } - if (fp) - return -1; - SET_RD(insn, regs, val.data_ulong << shift >> shift); + if (!fp) + SET_RD(insn, regs, val.data_ulong << shift >> shift); + else if (len == 8) + set_f64_rd(insn, regs, val.data_u64); + else + set_f32_rd(insn, regs, val.data_ulong); regs->epc = epc + INSN_LEN(insn); @@ -395,7 +510,7 @@ int handle_misaligned_store(struct pt_regs *regs) unsigned long epc = regs->epc; unsigned long insn; unsigned long addr = regs->badaddr; - int i, len = 0; + int i, len = 0, fp = 0; perf_sw_event(PERF_COUNT_SW_ALIGNMENT_FAULTS, 1, regs, addr); @@ -418,6 +533,14 @@ int handle_misaligned_store(struct pt_regs *regs) } else if ((insn & INSN_MASK_SD) == INSN_MATCH_SD) { len = 8; #endif + } else if ((insn & INSN_MASK_FSD) == INSN_MATCH_FSD) { + fp = 1; + len = 8; + val.data_u64 = GET_F64_RS2(insn, regs); + } else if ((insn & INSN_MASK_FSW) == INSN_MATCH_FSW) { + fp = 1; + len = 4; + val.data_ulong = GET_F32_RS2(insn, regs); } else if ((insn & INSN_MASK_SH) == INSN_MATCH_SH) { len = 2; #if defined(CONFIG_64BIT) @@ -436,11 +559,32 @@ int handle_misaligned_store(struct pt_regs *regs) ((insn >> SH_RD) & 0x1f)) { len = 4; val.data_ulong = GET_RS2C(insn, regs); + } else if ((insn & INSN_MASK_C_FSD) == INSN_MATCH_C_FSD) { + fp = 1; + len = 8; + val.data_u64 = GET_F64_RS2S(insn, regs); + } else if ((insn & INSN_MASK_C_FSDSP) == INSN_MATCH_C_FSDSP) { + fp = 1; + len = 8; + val.data_u64 = GET_F64_RS2C(insn, regs); +#if !defined(CONFIG_64BIT) + } else if ((insn & INSN_MASK_C_FSW) == INSN_MATCH_C_FSW) { + fp = 1; + len = 4; + val.data_ulong = GET_F32_RS2S(insn, regs); + } else if ((insn & INSN_MASK_C_FSWSP) == INSN_MATCH_C_FSWSP) { + fp = 1; + len = 4; + val.data_ulong = GET_F32_RS2C(insn, regs); +#endif } else { regs->epc = epc; return -1; } + if (!IS_ENABLED(CONFIG_FPU) && fp) + return -EOPNOTSUPP; + for (i = 0; i < len; i++) { if (store_u8(regs, (void *)(addr + i), val.data_bytes[i])) return -1; -- 2.40.1
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