1 files changed, 141 insertions, 6 deletions

diff --git a/arch/riscv/mm/cacheflush.c b/arch/riscv/mm/cacheflush.c
index bc61ee5975e4..4ca5aafce22e 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>
 
@@ -21,7 +22,22 @@ void flush_icache_all(void)
 {
 	local_flush_icache_all();
 
-	if (IS_ENABLED(CONFIG_RISCV_SBI) && !riscv_use_ipi_for_rfence())
+	if (num_online_cpus() < 2)
+		return;
+
+	/*
+	 * Make sure all previous writes to the D$ are ordered before making
+	 * the IPI. The RISC-V spec states that a hart must execute a data fence
+	 * before triggering a remote fence.i in order to make the modification
+	 * visable for remote harts.
+	 *
+	 * IPIs on RISC-V are triggered by MMIO writes to either CLINT or
+	 * S-IMSIC, so the fence ensures previous data writes "happen before"
+	 * the MMIO.
+	 */
+	RISCV_FENCE(w, o);
+
+	if (riscv_use_sbi_for_rfence())
 		sbi_remote_fence_i(NULL);
 	else
 		on_each_cpu(ipi_remote_fence_i, NULL, 1);
@@ -69,8 +85,7 @@ void flush_icache_mm(struct mm_struct *mm, bool local)
 		 * with flush_icache_deferred().
 		 */
 		smp_mb();
-	} else if (IS_ENABLED(CONFIG_RISCV_SBI) &&
-		   !riscv_use_ipi_for_rfence()) {
+	} else if (riscv_use_sbi_for_rfence()) {
 		sbi_remote_fence_i(&others);
 	} else {
 		on_each_cpu_mask(&others, ipi_remote_fence_i, NULL, 1);
@@ -99,6 +114,9 @@ EXPORT_SYMBOL_GPL(riscv_cbom_block_size);
 unsigned int riscv_cboz_block_size;
 EXPORT_SYMBOL_GPL(riscv_cboz_block_size);
 
+unsigned int riscv_cbop_block_size;
+EXPORT_SYMBOL_GPL(riscv_cbop_block_size);
+
 static void __init cbo_get_block_size(struct device_node *node,
 				      const char *name, u32 *block_size,
 				      unsigned long *first_hartid)
@@ -123,8 +141,8 @@ static void __init cbo_get_block_size(struct device_node *node,
 
 void __init riscv_init_cbo_blocksizes(void)
 {
-	unsigned long cbom_hartid, cboz_hartid;
-	u32 cbom_block_size = 0, cboz_block_size = 0;
+	unsigned long cbom_hartid, cboz_hartid, cbop_hartid;
+	u32 cbom_block_size = 0, cboz_block_size = 0, cbop_block_size = 0;
 	struct device_node *node;
 	struct acpi_table_header *rhct;
 	acpi_status status;
@@ -136,13 +154,15 @@ void __init riscv_init_cbo_blocksizes(void)
 					   &cbom_block_size, &cbom_hartid);
 			cbo_get_block_size(node, "riscv,cboz-block-size",
 					   &cboz_block_size, &cboz_hartid);
+			cbo_get_block_size(node, "riscv,cbop-block-size",
+					   &cbop_block_size, &cbop_hartid);
 		}
 	} else {
 		status = acpi_get_table(ACPI_SIG_RHCT, 0, &rhct);
 		if (ACPI_FAILURE(status))
 			return;
 
-		acpi_get_cbo_block_size(rhct, &cbom_block_size, &cboz_block_size, NULL);
+		acpi_get_cbo_block_size(rhct, &cbom_block_size, &cboz_block_size, &cbop_block_size);
 		acpi_put_table((struct acpi_table_header *)rhct);
 	}
 
@@ -151,4 +171,119 @@ void __init riscv_init_cbo_blocksizes(void)
 
 	if (cboz_block_size)
 		riscv_cboz_block_size = cboz_block_size;
+
+	if (cbop_block_size)
+		riscv_cbop_block_size = cbop_block_size;
+}
+
+#ifdef CONFIG_SMP
+static void set_icache_stale_mask(void)
+{
+	int cpu = get_cpu();
+	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 = &current->mm->context.icache_stale_mask;
+	stale_cpu = cpumask_test_cpu(cpu, mask);
+
+	cpumask_setall(mask);
+	__assign_cpu(cpu, mask, stale_cpu);
+	put_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:
+			set_icache_stale_mask();
+			current->mm->context.force_icache_flush = false;
+			break;
+		case PR_RISCV_SCOPE_PER_THREAD:
+			set_icache_stale_mask();
+			current->thread.force_icache_flush = false;
+			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
 }