diff options
| -rw-r--r-- | arch/riscv/include/asm/mmu.h | 2 | ||||
| -rw-r--r-- | arch/riscv/include/asm/processor.h | 10 | ||||
| -rw-r--r-- | arch/riscv/include/asm/switch_to.h | 23 | ||||
| -rw-r--r-- | arch/riscv/mm/cacheflush.c | 113 | ||||
| -rw-r--r-- | arch/riscv/mm/context.c | 19 | ||||
| -rw-r--r-- | include/uapi/linux/prctl.h | 6 | ||||
| -rw-r--r-- | kernel/sys.c | 6 |
7 files changed, 171 insertions, 8 deletions
diff --git a/arch/riscv/include/asm/mmu.h b/arch/riscv/include/asm/mmu.h index 355504b37f8e..60be458e94da 100644 --- a/arch/riscv/include/asm/mmu.h +++ b/arch/riscv/include/asm/mmu.h @@ -19,6 +19,8 @@ typedef struct { #ifdef CONFIG_SMP /* A local icache flush is needed before user execution can resume. */ cpumask_t icache_stale_mask; + /* Force local icache flush on all migrations. */ + bool force_icache_flush; #endif #ifdef CONFIG_BINFMT_ELF_FDPIC unsigned long exec_fdpic_loadmap; diff --git a/arch/riscv/include/asm/processor.h b/arch/riscv/include/asm/processor.h index a8509cc31ab2..cca62013c3c0 100644 --- a/arch/riscv/include/asm/processor.h +++ b/arch/riscv/include/asm/processor.h @@ -69,6 +69,7 @@ #endif #ifndef __ASSEMBLY__ +#include <linux/cpumask.h> struct task_struct; struct pt_regs; @@ -123,6 +124,12 @@ struct thread_struct { struct __riscv_v_ext_state vstate; unsigned long align_ctl; struct __riscv_v_ext_state kernel_vstate; +#ifdef CONFIG_SMP + /* Flush the icache on migration */ + bool force_icache_flush; + /* A forced icache flush is not needed if migrating to the previous cpu. */ + unsigned int prev_cpu; +#endif }; /* Whitelist the fstate from the task_struct for hardened usercopy */ @@ -184,6 +191,9 @@ extern int set_unalign_ctl(struct task_struct *tsk, unsigned int val); #define GET_UNALIGN_CTL(tsk, addr) get_unalign_ctl((tsk), (addr)) #define SET_UNALIGN_CTL(tsk, val) set_unalign_ctl((tsk), (val)) +#define RISCV_SET_ICACHE_FLUSH_CTX(arg1, arg2) riscv_set_icache_flush_ctx(arg1, arg2) +extern int riscv_set_icache_flush_ctx(unsigned long ctx, unsigned long per_thread); + #endif /* __ASSEMBLY__ */ #endif /* _ASM_RISCV_PROCESSOR_H */ diff --git a/arch/riscv/include/asm/switch_to.h b/arch/riscv/include/asm/switch_to.h index 7efdb0584d47..7594df37cc9f 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/mm_types.h> #include <asm/vector.h> #include <asm/cpufeature.h> #include <asm/processor.h> @@ -72,14 +73,36 @@ static __always_inline bool has_fpu(void) { return false; } extern struct task_struct *__switch_to(struct task_struct *, struct task_struct *); +static inline bool switch_to_should_flush_icache(struct task_struct *task) +{ +#ifdef CONFIG_SMP + bool stale_mm = task->mm && task->mm->context.force_icache_flush; + bool stale_thread = task->thread.force_icache_flush; + bool thread_migrated = smp_processor_id() != task->thread.prev_cpu; + + return thread_migrated && (stale_mm || stale_thread); +#else + return false; +#endif +} + +#ifdef CONFIG_SMP +#define __set_prev_cpu(thread) ((thread).prev_cpu = smp_processor_id()) +#else +#define __set_prev_cpu(thread) +#endif + #define switch_to(prev, next, last) \ do { \ struct task_struct *__prev = (prev); \ struct task_struct *__next = (next); \ + __set_prev_cpu(__prev->thread); \ if (has_fpu()) \ __switch_to_fpu(__prev, __next); \ if (has_vector()) \ __switch_to_vector(__prev, __next); \ + if (switch_to_should_flush_icache(__next)) \ + local_flush_icache_all(); \ ((last) = __switch_to(__prev, __next)); \ } while (0) diff --git a/arch/riscv/mm/cacheflush.c b/arch/riscv/mm/cacheflush.c index 55a34f2020a8..15a95578e670 100644 --- a/arch/riscv/mm/cacheflush.c +++ b/arch/riscv/mm/cacheflush.c @@ -5,6 +5,7 @@ #include <linux/acpi.h> #include <linux/of.h> +#include <linux/prctl.h> #include <asm/acpi.h> #include <asm/cacheflush.h> @@ -152,3 +153,115 @@ void __init riscv_init_cbo_blocksizes(void) if (cboz_block_size) riscv_cboz_block_size = cboz_block_size; } + +#ifdef CONFIG_SMP +static void set_icache_stale_mask(void) +{ + cpumask_t *mask; + bool stale_cpu; + + /* + * Mark every other hart's icache as needing a flush for + * this MM. Maintain the previous value of the current + * cpu to handle the case when this function is called + * concurrently on different harts. + */ + mask = ¤t->mm->context.icache_stale_mask; + stale_cpu = cpumask_test_cpu(smp_processor_id(), mask); + + cpumask_setall(mask); + assign_bit(cpumask_check(smp_processor_id()), cpumask_bits(mask), stale_cpu); +} +#endif + +/** + * riscv_set_icache_flush_ctx() - Enable/disable icache flushing instructions in + * userspace. + * @ctx: Set the type of icache flushing instructions permitted/prohibited in + * userspace. Supported values described below. + * + * Supported values for ctx: + * + * * %PR_RISCV_CTX_SW_FENCEI_ON: Allow fence.i in user space. + * + * * %PR_RISCV_CTX_SW_FENCEI_OFF: Disallow fence.i in user space. All threads in + * a process will be affected when ``scope == PR_RISCV_SCOPE_PER_PROCESS``. + * Therefore, caution must be taken; use this flag only when you can guarantee + * that no thread in the process will emit fence.i from this point onward. + * + * @scope: Set scope of where icache flushing instructions are allowed to be + * emitted. Supported values described below. + * + * Supported values for scope: + * + * * %PR_RISCV_SCOPE_PER_PROCESS: Ensure the icache of any thread in this process + * is coherent with instruction storage upon + * migration. + * + * * %PR_RISCV_SCOPE_PER_THREAD: Ensure the icache of the current thread is + * coherent with instruction storage upon + * migration. + * + * When ``scope == PR_RISCV_SCOPE_PER_PROCESS``, all threads in the process are + * permitted to emit icache flushing instructions. Whenever any thread in the + * process is migrated, the corresponding hart's icache will be guaranteed to be + * consistent with instruction storage. This does not enforce any guarantees + * outside of migration. If a thread modifies an instruction that another thread + * may attempt to execute, the other thread must still emit an icache flushing + * instruction before attempting to execute the potentially modified + * instruction. This must be performed by the user-space program. + * + * In per-thread context (eg. ``scope == PR_RISCV_SCOPE_PER_THREAD``) only the + * thread calling this function is permitted to emit icache flushing + * instructions. When the thread is migrated, the corresponding hart's icache + * will be guaranteed to be consistent with instruction storage. + * + * On kernels configured without SMP, this function is a nop as migrations + * across harts will not occur. + */ +int riscv_set_icache_flush_ctx(unsigned long ctx, unsigned long scope) +{ +#ifdef CONFIG_SMP + switch (ctx) { + case PR_RISCV_CTX_SW_FENCEI_ON: + switch (scope) { + case PR_RISCV_SCOPE_PER_PROCESS: + current->mm->context.force_icache_flush = true; + break; + case PR_RISCV_SCOPE_PER_THREAD: + current->thread.force_icache_flush = true; + break; + default: + return -EINVAL; + } + break; + case PR_RISCV_CTX_SW_FENCEI_OFF: + switch (scope) { + case PR_RISCV_SCOPE_PER_PROCESS: + current->mm->context.force_icache_flush = false; + + set_icache_stale_mask(); + break; + case PR_RISCV_SCOPE_PER_THREAD: + current->thread.force_icache_flush = false; + + set_icache_stale_mask(); + break; + default: + return -EINVAL; + } + break; + default: + return -EINVAL; + } + return 0; +#else + switch (ctx) { + case PR_RISCV_CTX_SW_FENCEI_ON: + case PR_RISCV_CTX_SW_FENCEI_OFF: + return 0; + default: + return -EINVAL; + } +#endif +} diff --git a/arch/riscv/mm/context.c b/arch/riscv/mm/context.c index 217fd4de6134..beef30f42d5c 100644 --- a/arch/riscv/mm/context.c +++ b/arch/riscv/mm/context.c @@ -15,6 +15,7 @@ #include <asm/tlbflush.h> #include <asm/cacheflush.h> #include <asm/mmu_context.h> +#include <asm/switch_to.h> #ifdef CONFIG_MMU @@ -297,21 +298,23 @@ static inline void set_mm(struct mm_struct *prev, * * The "cpu" argument must be the current local CPU number. */ -static inline void flush_icache_deferred(struct mm_struct *mm, unsigned int cpu) +static inline void flush_icache_deferred(struct mm_struct *mm, unsigned int cpu, + struct task_struct *task) { #ifdef CONFIG_SMP - cpumask_t *mask = &mm->context.icache_stale_mask; - - if (cpumask_test_cpu(cpu, mask)) { - cpumask_clear_cpu(cpu, mask); + if (cpumask_test_and_clear_cpu(cpu, &mm->context.icache_stale_mask)) { /* * Ensure the remote hart's writes are visible to this hart. * This pairs with a barrier in flush_icache_mm. */ smp_mb(); - local_flush_icache_all(); - } + /* + * If cache will be flushed in switch_to, no need to flush here. + */ + if (!(task && switch_to_should_flush_icache(task))) + local_flush_icache_all(); + } #endif } @@ -332,5 +335,5 @@ void switch_mm(struct mm_struct *prev, struct mm_struct *next, set_mm(prev, next, cpu); - flush_icache_deferred(next, cpu); + flush_icache_deferred(next, cpu, task); } diff --git a/include/uapi/linux/prctl.h b/include/uapi/linux/prctl.h index 370ed14b1ae0..524d546d697b 100644 --- a/include/uapi/linux/prctl.h +++ b/include/uapi/linux/prctl.h @@ -306,4 +306,10 @@ struct prctl_mm_map { # define PR_RISCV_V_VSTATE_CTRL_NEXT_MASK 0xc # define PR_RISCV_V_VSTATE_CTRL_MASK 0x1f +#define PR_RISCV_SET_ICACHE_FLUSH_CTX 71 +# define PR_RISCV_CTX_SW_FENCEI_ON 0 +# define PR_RISCV_CTX_SW_FENCEI_OFF 1 +# define PR_RISCV_SCOPE_PER_PROCESS 0 +# define PR_RISCV_SCOPE_PER_THREAD 1 + #endif /* _LINUX_PRCTL_H */ diff --git a/kernel/sys.c b/kernel/sys.c index e219fcfa112d..69afdd8b430f 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -146,6 +146,9 @@ #ifndef RISCV_V_GET_CONTROL # define RISCV_V_GET_CONTROL() (-EINVAL) #endif +#ifndef RISCV_SET_ICACHE_FLUSH_CTX +# define RISCV_SET_ICACHE_FLUSH_CTX(a, b) (-EINVAL) +#endif /* * this is where the system-wide overflow UID and GID are defined, for @@ -2743,6 +2746,9 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3, case PR_RISCV_V_GET_CONTROL: error = RISCV_V_GET_CONTROL(); break; + case PR_RISCV_SET_ICACHE_FLUSH_CTX: + error = RISCV_SET_ICACHE_FLUSH_CTX(arg2, arg3); + break; default: error = -EINVAL; break; |