linux-kernel - [PATCH v2 6/8] riscv: smp: use NMI for backtrace

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Message-Id: <20251118025015.42491-7-cuiyunhui@bytedance.com>
Date: Tue, 18 Nov 2025 10:50:13 +0800
From: Yunhui Cui <cuiyunhui@...edance.com>
To: conor@...nel.org,
	paul.walmsley@...ive.com,
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Subject: [PATCH v2 6/8] riscv: smp: use NMI for backtrace

Use NMI instead of IPI for backtrace if RISC-V SSE NMI is supported.

Signed-off-by: Yunhui Cui <cuiyunhui@...edance.com>
---
 arch/riscv/kernel/smp.c                | 12 +++++++++++-
 drivers/firmware/riscv/riscv_sse_nmi.c |  2 ++
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/arch/riscv/kernel/smp.c b/arch/riscv/kernel/smp.c
index aa1cfc344a2c6..26083fe0a5df6 100644
--- a/arch/riscv/kernel/smp.c
+++ b/arch/riscv/kernel/smp.c
@@ -356,9 +356,19 @@ static void riscv_backtrace_ipi(cpumask_t *mask)
 	send_ipi_mask(mask, IPI_CPU_BACKTRACE);
 }
 
+static void riscv_backtrace_nmi(cpumask_t *mask)
+{
+	send_nmi_mask(mask, LOCAL_NMI_BACKTRACE);
+}
+
 void arch_trigger_cpumask_backtrace(const cpumask_t *mask, int exclude_cpu)
 {
-	nmi_trigger_cpumask_backtrace(mask, exclude_cpu, riscv_backtrace_ipi);
+	if (!nmi_support())
+		nmi_trigger_cpumask_backtrace(mask, exclude_cpu,
+					      riscv_backtrace_ipi);
+	else
+		nmi_trigger_cpumask_backtrace(mask, exclude_cpu,
+					      riscv_backtrace_nmi);
 }
 
 #ifdef CONFIG_KGDB
diff --git a/drivers/firmware/riscv/riscv_sse_nmi.c b/drivers/firmware/riscv/riscv_sse_nmi.c
index 0ff0bda53608a..cac940b7e8773 100644
--- a/drivers/firmware/riscv/riscv_sse_nmi.c
+++ b/drivers/firmware/riscv/riscv_sse_nmi.c
@@ -3,6 +3,7 @@
 #define pr_fmt(fmt) "SSE NMI: " fmt
 
 #include <linux/atomic.h>
+#include <linux/nmi.h>
 #include <linux/riscv_sbi_sse.h>
 #include <linux/riscv_sse_nmi.h>
 
@@ -56,6 +57,7 @@ static int local_nmi_handler(u32 evt, void *arg, struct pt_regs *regs)
 
 	NMI_HANDLE(LOCAL_NMI_CRASH, cpu_crash_stop, cpu, regs);
 	NMI_HANDLE(LOCAL_NMI_STOP, cpu_stop);
+	NMI_HANDLE(LOCAL_NMI_BACKTRACE, nmi_cpu_backtrace, regs);
 
 	atomic_set(&local_nmi_arg, LOCAL_NMI_NONE);
 
-- 
2.39.5