Messages in this thread Patch in this message | | | From | Greentime Hu <> | Subject | [RFC PATCH v8 21/21] riscv: Turn has_vector into a static key if VECTOR=y | Date | Thu, 9 Sep 2021 01:45:33 +0800 |
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Just like fpu, we can use static key for has_vector. The has_vector check sits at hot code path: switch_to(). Currently, has_vector is a bool variable if VECTOR=y, switch_to() checks it each time, we can optimize out this check by turning the has_vector into a static key.
Signed-off-by: Greentime Hu <greentime.hu@sifive.com> --- arch/riscv/include/asm/switch_to.h | 10 +++++++--- arch/riscv/kernel/cpufeature.c | 4 ++-- arch/riscv/kernel/kernel_mode_vector.c | 4 ++-- arch/riscv/kernel/process.c | 8 ++++---- arch/riscv/kernel/signal.c | 6 +++--- 5 files changed, 18 insertions(+), 14 deletions(-)
diff --git a/arch/riscv/include/asm/switch_to.h b/arch/riscv/include/asm/switch_to.h index b48c9c974564..576204217e0f 100644 --- a/arch/riscv/include/asm/switch_to.h +++ b/arch/riscv/include/asm/switch_to.h @@ -71,7 +71,11 @@ static __always_inline bool has_fpu(void) { return false; } #endif #ifdef CONFIG_VECTOR -extern bool has_vector; +extern struct static_key_false cpu_hwcap_vector; +static __always_inline bool has_vector(void) +{ + return static_branch_likely(&cpu_hwcap_vector); +} extern unsigned long riscv_vsize; extern void __vstate_save(struct __riscv_v_state *save_to, void *datap); extern void __vstate_restore(struct __riscv_v_state *restore_from, void *datap); @@ -120,7 +124,7 @@ static inline void __switch_to_vector(struct task_struct *prev, } #else -#define has_vector false +static __always_inline bool has_vector(void) { return false; } #define riscv_vsize (0) #define vstate_save(task, regs) do { } while (0) #define vstate_restore(task, regs) do { } while (0) @@ -136,7 +140,7 @@ do { \ struct task_struct *__next = (next); \ if (has_fpu()) \ __switch_to_fpu(__prev, __next); \ - if (has_vector) \ + if (has_vector()) \ __switch_to_vector(__prev, __next); \ ((last) = __switch_to(__prev, __next)); \ } while (0) diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c index af984f875f60..0139ec20adce 100644 --- a/arch/riscv/kernel/cpufeature.c +++ b/arch/riscv/kernel/cpufeature.c @@ -23,7 +23,7 @@ __ro_after_init DEFINE_STATIC_KEY_FALSE(cpu_hwcap_fpu); #endif #ifdef CONFIG_VECTOR #include <asm/vector.h> -bool has_vector __read_mostly; +__ro_after_init DEFINE_STATIC_KEY_FALSE(cpu_hwcap_vector); unsigned long riscv_vsize __read_mostly; #endif @@ -157,7 +157,7 @@ void __init riscv_fill_hwcap(void) #ifdef CONFIG_VECTOR if (elf_hwcap & COMPAT_HWCAP_ISA_V) { - has_vector = true; + static_branch_enable(&cpu_hwcap_vector); /* There are 32 vector registers with vlenb length. */ rvv_enable(); riscv_vsize = csr_read(CSR_VLENB) * 32; diff --git a/arch/riscv/kernel/kernel_mode_vector.c b/arch/riscv/kernel/kernel_mode_vector.c index 0d990bd8b8dd..0d08954c30af 100644 --- a/arch/riscv/kernel/kernel_mode_vector.c +++ b/arch/riscv/kernel/kernel_mode_vector.c @@ -110,7 +110,7 @@ static void vector_flush_cpu_state(void) */ void kernel_rvv_begin(void) { - if (WARN_ON(!has_vector)) + if (WARN_ON(!has_vector())) return; WARN_ON(!may_use_vector()); @@ -140,7 +140,7 @@ EXPORT_SYMBOL(kernel_rvv_begin); */ void kernel_rvv_end(void) { - if (WARN_ON(!has_vector)) + if (WARN_ON(!has_vector())) return; /* Invalidate vector regs */ diff --git a/arch/riscv/kernel/process.c b/arch/riscv/kernel/process.c index 05ff5f934e7e..62540815ba1c 100644 --- a/arch/riscv/kernel/process.c +++ b/arch/riscv/kernel/process.c @@ -96,7 +96,7 @@ void start_thread(struct pt_regs *regs, unsigned long pc, fstate_restore(current, regs); } - if (has_vector) { + if (has_vector()) { struct __riscv_v_state *vstate = &(current->thread.vstate); /* Enable vector and allocate memory for vector registers. */ @@ -141,11 +141,11 @@ void flush_thread(void) int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src) { fstate_save(src, task_pt_regs(src)); - if (has_vector) + if (has_vector()) /* To make sure every dirty vector context is saved. */ vstate_save(src, task_pt_regs(src)); *dst = *src; - if (has_vector) { + if (has_vector()) { /* Copy vector context to the forked task from parent. */ if ((task_pt_regs(src)->status & SR_VS) != SR_VS_OFF) { dst->thread.vstate.datap = kzalloc(riscv_vsize, GFP_KERNEL); @@ -164,7 +164,7 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src) void arch_release_task_struct(struct task_struct *tsk) { /* Free the vector context of datap. */ - if (has_vector) + if (has_vector()) kfree(tsk->thread.vstate.datap); } diff --git a/arch/riscv/kernel/signal.c b/arch/riscv/kernel/signal.c index d30a3b588156..6a19b4b7b206 100644 --- a/arch/riscv/kernel/signal.c +++ b/arch/riscv/kernel/signal.c @@ -192,7 +192,7 @@ static long restore_sigcontext(struct pt_regs *regs, goto invalid; goto done; case RVV_MAGIC: - if (!has_vector) + if (!has_vector()) goto invalid; if (size != rvv_sc_size) goto invalid; @@ -221,7 +221,7 @@ static size_t cal_rt_frame_size(void) frame_size = sizeof(*frame); - if (has_vector) + if (has_vector()) total_context_size += rvv_sc_size; /* Preserved a __riscv_ctx_hdr for END signal context header. */ total_context_size += sizeof(struct __riscv_ctx_hdr); @@ -288,7 +288,7 @@ static long setup_sigcontext(struct rt_sigframe __user *frame, if (has_fpu()) err |= save_fp_state(regs, &sc->sc_fpregs); /* Save the vector state. */ - if (has_vector) + if (has_vector()) err |= save_v_state(regs, &sc_reserved_free_ptr); /* Put END __riscv_ctx_hdr at the end. */ -- 2.31.1
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