#endif /* _ASM_RISCV_SWITCH_TO_H */
diff --git a/arch/riscv/mm/cacheflush.c b/arch/riscv/mm/cacheflush.c
index 55a34f2020a8..ff545f19f07a 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 +153,69 @@ void __init riscv_init_cbo_blocksizes(void)
if (cboz_block_size)
riscv_cboz_block_size = cboz_block_size;
}
+
+/**
+ * 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 userspace.
+ *
+ * * %PR_RISCV_CTX_SW_FENCEI_OFF: Disallow fence.i in userspace. When ``scope ==
+ * PR_RISCV_SCOPE_PER_PROCESS``, this will effect all threads in a process.
+ * Therefore, caution must be taken -- only use this flag 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. Note 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 userspace 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;
+ }
+ }
+#endif
+ return 0;
+}
diff --git a/arch/riscv/mm/context.c b/arch/riscv/mm/context.c
index 217fd4de6134..b059dc0fae91 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
@@ -297,19 +298,26 @@ 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);
+
/*
* 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 +340,5 @@ 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 420d9cb9cc8e..e806a8a67c36 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
@@ -2739,6 +2742,9 @@ 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;
