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Message-Id: <56e2328d133045c79b420ecbcaf37cf9d0b2248c.1631121222.git.greentime.hu@sifive.com>
Date: Thu, 9 Sep 2021 01:45:33 +0800
From: Greentime Hu <greentime.hu@...ive.com>
To: linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
aou@...s.berkeley.edu, palmer@...belt.com,
paul.walmsley@...ive.com, vincent.chen@...ive.com
Subject: [RFC PATCH v8 21/21] riscv: Turn has_vector into a static key if VECTOR=y
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@...ive.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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