Merge patch series "riscv: fix patching with IPI"

Alexandre Ghiti <alexghiti@rivosinc.com> says:

patch 1 removes a useless memory barrier and patch 2 actually fixes the
issue with IPI in the patching code.

* b4-shazam-merge:
  riscv: Fix text patching when IPI are used
  riscv: Remove superfluous smp_mb()

Link: https://lore.kernel.org/r/20240229121056.203419-1-alexghiti@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

1 files changed, 40 insertions, 4 deletions

diff --git a/arch/riscv/kernel/ftrace.c b/arch/riscv/kernel/ftrace.c
index f5aa24d9e1c1..4f4987a6d83d 100644
--- a/arch/riscv/kernel/ftrace.c
+++ b/arch/riscv/kernel/ftrace.c
@@ -8,6 +8,7 @@
 #include <linux/ftrace.h>
 #include <linux/uaccess.h>
 #include <linux/memory.h>
+#include <linux/stop_machine.h>
 #include <asm/cacheflush.h>
 #include <asm/patch.h>
 
@@ -75,8 +76,7 @@ static int __ftrace_modify_call(unsigned long hook_pos, unsigned long target,
 		make_call_t0(hook_pos, target, call);
 
 	/* Replace the auipc-jalr pair at once. Return -EPERM on write error. */
-	if (patch_text_nosync
-	    ((void *)hook_pos, enable ? call : nops, MCOUNT_INSN_SIZE))
+	if (patch_insn_write((void *)hook_pos, enable ? call : nops, MCOUNT_INSN_SIZE))
 		return -EPERM;
 
 	return 0;
@@ -88,7 +88,7 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 
 	make_call_t0(rec->ip, addr, call);
 
-	if (patch_text_nosync((void *)rec->ip, call, MCOUNT_INSN_SIZE))
+	if (patch_insn_write((void *)rec->ip, call, MCOUNT_INSN_SIZE))
 		return -EPERM;
 
 	return 0;
@@ -99,7 +99,7 @@ int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
 {
 	unsigned int nops[2] = {NOP4, NOP4};
 
-	if (patch_text_nosync((void *)rec->ip, nops, MCOUNT_INSN_SIZE))
+	if (patch_insn_write((void *)rec->ip, nops, MCOUNT_INSN_SIZE))
 		return -EPERM;
 
 	return 0;
@@ -134,6 +134,42 @@ int ftrace_update_ftrace_func(ftrace_func_t func)
 
 	return ret;
 }
+
+struct ftrace_modify_param {
+	int command;
+	atomic_t cpu_count;
+};
+
+static int __ftrace_modify_code(void *data)
+{
+	struct ftrace_modify_param *param = data;
+
+	if (atomic_inc_return(&param->cpu_count) == num_online_cpus()) {
+		ftrace_modify_all_code(param->command);
+		/*
+		 * Make sure the patching store is effective *before* we
+		 * increment the counter which releases all waiting CPUs
+		 * by using the release variant of atomic increment. The
+		 * release pairs with the call to local_flush_icache_all()
+		 * on the waiting CPU.
+		 */
+		atomic_inc_return_release(&param->cpu_count);
+	} else {
+		while (atomic_read(&param->cpu_count) <= num_online_cpus())
+			cpu_relax();
+	}
+
+	local_flush_icache_all();
+
+	return 0;
+}
+
+void arch_ftrace_update_code(int command)
+{
+	struct ftrace_modify_param param = { command, ATOMIC_INIT(0) };
+
+	stop_machine(__ftrace_modify_code, &param, cpu_online_mask);
+}
 #endif
 
 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS