[PATCH -next v21 10/27] riscv: Add task switch support for vector

Andy Chiu
2023-06-05T15:41:54Z

From: Greentime Hu <greentime.hu@sifive.com>

This patch adds task switch support for vector. It also supports all
lengths of vlen.

Suggested-by: Andrew Waterman <andrew@sifive.com>
Co-developed-by: Nick Knight <nick.knight@sifive.com>
Signed-off-by: Nick Knight <nick.knight@sifive.com>
Co-developed-by: Guo Ren <guoren@linux.alibaba.com>
Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
Co-developed-by: Vincent Chen <vincent.chen@sifive.com>
Signed-off-by: Vincent Chen <vincent.chen@sifive.com>
Co-developed-by: Ruinland Tsai <ruinland.tsai@sifive.com>
Signed-off-by: Ruinland Tsai <ruinland.tsai@sifive.com>
Signed-off-by: Greentime Hu <greentime.hu@sifive.com>
Signed-off-by: Vineet Gupta <vineetg@rivosinc.com>
Signed-off-by: Andy Chiu <andy.chiu@sifive.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Björn Töpel <bjorn@rivosinc.com>
Reviewed-by: Heiko Stuebner <heiko.stuebner@vrull.eu>
Tested-by: Heiko Stuebner <heiko.stuebner@vrull.eu>
---
Changelog v21:
- move riscv_v_vstate_off(childregs); to a proper place.
---
arch/riscv/include/asm/processor.h | 1 +
arch/riscv/include/asm/switch_to.h | 3 +++
arch/riscv/include/asm/thread_info.h | 3 +++
arch/riscv/include/asm/vector.h | 38 ++++++++++++++++++++++++++++
arch/riscv/kernel/process.c | 19 ++++++++++++++
5 files changed, 64 insertions(+)

diff --git a/arch/riscv/include/asm/processor.h b/arch/riscv/include/asm/processor.h
index 94a0590c6971..f0ddf691ac5e 100644
--- a/arch/riscv/include/asm/processor.h
+++ b/arch/riscv/include/asm/processor.h
@@ -39,6 +39,7 @@ struct thread_struct {
unsigned long s[12]; /* s[0]: frame pointer */
struct __riscv_d_ext_state fstate;
unsigned long bad_cause;
+ struct __riscv_v_ext_state vstate;
};

/* Whitelist the fstate from the task_struct for hardened usercopy */
diff --git a/arch/riscv/include/asm/switch_to.h b/arch/riscv/include/asm/switch_to.h
index 4b96b13dee27..a727be723c56 100644
--- a/arch/riscv/include/asm/switch_to.h
+++ b/arch/riscv/include/asm/switch_to.h
@@ -8,6 +8,7 @@

#include <linux/jump_label.h>
#include <linux/sched/task_stack.h>
+#include <asm/vector.h>
#include <asm/hwcap.h>
#include <asm/processor.h>
#include <asm/ptrace.h>
@@ -78,6 +79,8 @@ do { \
struct task_struct *__next = (next); \
if (has_fpu()) \
__switch_to_fpu(__prev, __next); \
+ if (has_vector()) \
+ __switch_to_vector(__prev, __next); \
((last) = __switch_to(__prev, __next)); \
} while (0)

diff --git a/arch/riscv/include/asm/thread_info.h b/arch/riscv/include/asm/thread_info.h
index e0d202134b44..97e6f65ec176 100644
--- a/arch/riscv/include/asm/thread_info.h
+++ b/arch/riscv/include/asm/thread_info.h
@@ -81,6 +81,9 @@ struct thread_info {
.preempt_count = INIT_PREEMPT_COUNT, \
}

+void arch_release_task_struct(struct task_struct *tsk);
+int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src);
+
#endif /* !__ASSEMBLY__ */

/*
diff --git a/arch/riscv/include/asm/vector.h b/arch/riscv/include/asm/vector.h
index 3c29f4eb552a..ce6a75e9cf62 100644
--- a/arch/riscv/include/asm/vector.h
+++ b/arch/riscv/include/asm/vector.h
@@ -12,6 +12,9 @@
#ifdef CONFIG_RISCV_ISA_V

#include <linux/stringify.h>
+#include <linux/sched.h>
+#include <linux/sched/task_stack.h>
+#include <asm/ptrace.h>
#include <asm/hwcap.h>
#include <asm/csr.h>
#include <asm/asm.h>
@@ -124,6 +127,38 @@ static inline void __riscv_v_vstate_restore(struct __riscv_v_ext_state *restore_
riscv_v_disable();
}

+static inline void riscv_v_vstate_save(struct task_struct *task,
+ struct pt_regs *regs)
+{
+ if ((regs->status & SR_VS) == SR_VS_DIRTY) {
+ struct __riscv_v_ext_state *vstate = &task->thread.vstate;
+
+ __riscv_v_vstate_save(vstate, vstate->datap);
+ __riscv_v_vstate_clean(regs);
+ }
+}
+
+static inline void riscv_v_vstate_restore(struct task_struct *task,
+ struct pt_regs *regs)
+{
+ if ((regs->status & SR_VS) != SR_VS_OFF) {
+ struct __riscv_v_ext_state *vstate = &task->thread.vstate;
+
+ __riscv_v_vstate_restore(vstate, vstate->datap);
+ __riscv_v_vstate_clean(regs);
+ }
+}
+
+static inline void __switch_to_vector(struct task_struct *prev,
+ struct task_struct *next)
+{
+ struct pt_regs *regs;
+
+ regs = task_pt_regs(prev);
+ riscv_v_vstate_save(prev, regs);
+ riscv_v_vstate_restore(next, task_pt_regs(next));
+}
+
#else /* ! CONFIG_RISCV_ISA_V */

struct pt_regs;
@@ -132,6 +167,9 @@ static inline int riscv_v_setup_vsize(void) { return -EOPNOTSUPP; }
static __always_inline bool has_vector(void) { return false; }
static inline bool riscv_v_vstate_query(struct pt_regs *regs) { return false; }
#define riscv_v_vsize (0)
+#define riscv_v_vstate_save(task, regs) do {} while (0)
+#define riscv_v_vstate_restore(task, regs) do {} while (0)
+#define __switch_to_vector(__prev, __next) do {} while (0)
#define riscv_v_vstate_off(regs) do {} while (0)
#define riscv_v_vstate_on(regs) do {} while (0)

diff --git a/arch/riscv/kernel/process.c b/arch/riscv/kernel/process.c
index e2a060066730..78eb5ac45888 100644
--- a/arch/riscv/kernel/process.c
+++ b/arch/riscv/kernel/process.c
@@ -24,6 +24,7 @@
#include <asm/switch_to.h>
#include <asm/thread_info.h>
#include <asm/cpuidle.h>
+#include <asm/vector.h>

register unsigned long gp_in_global __asm__("gp");

@@ -146,12 +147,28 @@ void flush_thread(void)
fstate_off(current, task_pt_regs(current));
memset(&current->thread.fstate, 0, sizeof(current->thread.fstate));
#endif
+#ifdef CONFIG_RISCV_ISA_V
+ /* Reset vector state */
+ riscv_v_vstate_off(task_pt_regs(current));
+ kfree(current->thread.vstate.datap);
+ memset(&current->thread.vstate, 0, sizeof(struct __riscv_v_ext_state));
+#endif
+}
+
+void arch_release_task_struct(struct task_struct *tsk)
+{
+ /* Free the vector context of datap. */
+ if (has_vector())
+ kfree(tsk->thread.vstate.datap);
}

int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
{
fstate_save(src, task_pt_regs(src));
*dst = *src;
+ /* clear entire V context, including datap for a new task */
+ memset(&dst->thread.vstate, 0, sizeof(struct __riscv_v_ext_state));
+
return 0;
}

@@ -176,6 +193,8 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
p->thread.s[1] = (unsigned long)args->fn_arg;
} else {
*childregs = *(current_pt_regs());
+ /* Turn off status.VS */
+ riscv_v_vstate_off(childregs);
if (usp) /* User fork */
childregs->sp = usp;
if (clone_flags & CLONE_SETTLS)
--
2.17.1