[PATCH -next v20 10/26] riscv: Add task switch support for vector
Palmer Dabbelt
palmer at dabbelt.com
Tue May 23 17:49:03 PDT 2023
On Thu, 18 May 2023 09:19:33 PDT (-0700), andy.chiu at sifive.com wrote:
> From: Greentime Hu <greentime.hu at sifive.com>
>
> This patch adds task switch support for vector. It also supports all
> lengths of vlen.
>
> Suggested-by: Andrew Waterman <andrew at sifive.com>
> Co-developed-by: Nick Knight <nick.knight at sifive.com>
> Signed-off-by: Nick Knight <nick.knight at sifive.com>
> Co-developed-by: Guo Ren <guoren at linux.alibaba.com>
> Signed-off-by: Guo Ren <guoren at linux.alibaba.com>
> Co-developed-by: Vincent Chen <vincent.chen at sifive.com>
> Signed-off-by: Vincent Chen <vincent.chen at sifive.com>
> Co-developed-by: Ruinland Tsai <ruinland.tsai at sifive.com>
> Signed-off-by: Ruinland Tsai <ruinland.tsai at sifive.com>
> Signed-off-by: Greentime Hu <greentime.hu at sifive.com>
> Signed-off-by: Vineet Gupta <vineetg at rivosinc.com>
> Signed-off-by: Andy Chiu <andy.chiu at sifive.com>
> Reviewed-by: Conor Dooley <conor.dooley at microchip.com>
> Reviewed-by: Björn Töpel <bjorn at rivosinc.com>
> Reviewed-by: Heiko Stuebner <heiko.stuebner at vrull.eu>
> Tested-by: Heiko Stuebner <heiko.stuebner at vrull.eu>
> ---
> 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 | 18 +++++++++++++
> 5 files changed, 63 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..b7a10361ddc6 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(¤t->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(¤t->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;
> }
>
> @@ -184,6 +201,7 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
> p->thread.s[0] = 0;
> }
> p->thread.ra = (unsigned long)ret_from_fork;
> + riscv_v_vstate_off(childregs);
When is V still on at this point? If we got here via clone() (or any
other syscall) it should be off already, so if we need to turn it off
here then we must have arrived via something that's not a syscall. I
don't know what that case is, so it's not clear we can just throw away
the V state.
> p->thread.sp = (unsigned long)childregs; /* kernel sp */
> return 0;
> }
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