Write the next task PID to the scontext CSR if the use_scontext static branch is enabled by the detection of the cpufeature.c
The scontext CSR needs to be saved and restored when entering a non-retentive idle state so that when resuming the CPU, the task's PID on the scontext CSR will be correct.
Co-developed-by: Nick Hu nick.hu@sifive.com Signed-off-by: Nick Hu nick.hu@sifive.com Signed-off-by: Max Hsu max.hsu@sifive.com --- arch/riscv/include/asm/suspend.h | 1 + arch/riscv/include/asm/switch_to.h | 9 +++++++++ arch/riscv/kernel/suspend.c | 7 +++++++ 3 files changed, 17 insertions(+)
diff --git a/arch/riscv/include/asm/suspend.h b/arch/riscv/include/asm/suspend.h index 2ecace073869..5021cad7e815 100644 --- a/arch/riscv/include/asm/suspend.h +++ b/arch/riscv/include/asm/suspend.h @@ -13,6 +13,7 @@ struct suspend_context { /* Saved and restored by low-level functions */ struct pt_regs regs; /* Saved and restored by high-level functions */ + unsigned long scontext; unsigned long scratch; unsigned long envcfg; unsigned long tvec; diff --git a/arch/riscv/include/asm/switch_to.h b/arch/riscv/include/asm/switch_to.h index 07432550ed54..289cd6b60978 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 <linux/pid.h> #include <asm/vector.h> #include <asm/cpufeature.h> #include <asm/processor.h> @@ -75,6 +76,12 @@ static __always_inline bool has_scontext(void) return static_branch_likely(&use_scontext); }
+static __always_inline void __switch_to_scontext(struct task_struct *__prev, + struct task_struct *__next) +{ + csr_write(CSR_SCONTEXT, task_pid_nr(__next)); +} + extern struct task_struct *__switch_to(struct task_struct *, struct task_struct *);
@@ -86,6 +93,8 @@ do { \ __switch_to_fpu(__prev, __next); \ if (has_vector()) \ __switch_to_vector(__prev, __next); \ + if (has_scontext()) \ + __switch_to_scontext(__prev, __next); \ ((last) = __switch_to(__prev, __next)); \ } while (0)
diff --git a/arch/riscv/kernel/suspend.c b/arch/riscv/kernel/suspend.c index a086da222872..6b403a1f75c3 100644 --- a/arch/riscv/kernel/suspend.c +++ b/arch/riscv/kernel/suspend.c @@ -11,9 +11,13 @@ #include <asm/csr.h> #include <asm/sbi.h> #include <asm/suspend.h> +#include <asm/switch_to.h>
void suspend_save_csrs(struct suspend_context *context) { + if (has_scontext()) + context->scontext = csr_read(CSR_SCONTEXT); + context->scratch = csr_read(CSR_SCRATCH); if (riscv_cpu_has_extension_unlikely(smp_processor_id(), RISCV_ISA_EXT_XLINUXENVCFG)) context->envcfg = csr_read(CSR_ENVCFG); @@ -46,6 +50,9 @@ void suspend_save_csrs(struct suspend_context *context)
void suspend_restore_csrs(struct suspend_context *context) { + if (has_scontext()) + csr_write(CSR_SCONTEXT, context->scontext); + csr_write(CSR_SCRATCH, context->scratch); if (riscv_cpu_has_extension_unlikely(smp_processor_id(), RISCV_ISA_EXT_XLINUXENVCFG)) csr_write(CSR_ENVCFG, context->envcfg);