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Mon, 17 Nov 2025 18:51:38 -0800 (PST) From: Yunhui Cui To: conor@kernel.org, paul.walmsley@sifive.com, palmer@dabbelt.com, aou@eecs.berkeley.edu, alex@ghiti.fr, cuiyunhui@bytedance.com, luxu.kernel@bytedance.com, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, jassisinghbrar@gmail.com, conor.dooley@microchip.com, valentina.fernandezalanis@microchip.com, catalin.marinas@arm.com, will@kernel.org, maz@kernel.org, timothy.hayes@arm.com, lpieralisi@kernel.org, arnd@arndb.de, kees@kernel.org, tglx@linutronix.de, viresh.kumar@linaro.org, boqun.feng@gmail.com, linux-arm-kernel@lists.infradead.org, cleger@rivosinc.com, atishp@rivosinc.com, ajones@ventanamicro.com Subject: [PATCH v2 8/8] drivers: firmware: riscv: add unknown nmi support Date: Tue, 18 Nov 2025 10:50:15 +0800 Message-Id: <20251118025015.42491-9-cuiyunhui@bytedance.com> X-Mailer: git-send-email 2.39.2 (Apple Git-143) In-Reply-To: <20251118025015.42491-1-cuiyunhui@bytedance.com> References: <20251118025015.42491-1-cuiyunhui@bytedance.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Register unknown_nmi_handler() as the handler for the UNKNOWN_NMI event. When the system becomes unresponsive, unknown_nmi_handler() can be manually triggered, which in turn invokes nmi_panic() to collect vmcore for root cause analysis. Signed-off-by: Yunhui Cui --- arch/riscv/include/asm/sbi.h | 1 + drivers/firmware/riscv/riscv_sse_nmi.c | 68 ++++++++++++++++++++++++++ 2 files changed, 69 insertions(+) diff --git a/arch/riscv/include/asm/sbi.h b/arch/riscv/include/asm/sbi.h index 874cc1d7603a5..52d3fdf2d4cc1 100644 --- a/arch/riscv/include/asm/sbi.h +++ b/arch/riscv/include/asm/sbi.h @@ -486,6 +486,7 @@ enum sbi_sse_attr_id { #define SBI_SSE_EVENT_LOCAL_LOW_PRIO_RAS 0x00100000 #define SBI_SSE_EVENT_GLOBAL_LOW_PRIO_RAS 0x00108000 #define SBI_SSE_EVENT_LOCAL_SOFTWARE_INJECTED 0xffff0000 +#define SBI_SSE_EVENT_LOCAL_UNKNOWN_NMI 0xffff0001 #define SBI_SSE_EVENT_GLOBAL_SOFTWARE_INJECTED 0xffff8000 =20 #define SBI_SSE_EVENT_PLATFORM BIT(14) diff --git a/drivers/firmware/riscv/riscv_sse_nmi.c b/drivers/firmware/risc= v/riscv_sse_nmi.c index 5035d4ec485f6..e895abf583bd5 100644 --- a/drivers/firmware/riscv/riscv_sse_nmi.c +++ b/drivers/firmware/riscv/riscv_sse_nmi.c @@ -7,6 +7,7 @@ #include #include #include +#include =20 #include #include @@ -16,7 +17,10 @@ do { if (type & (mask)) func(__VA_ARGS__); } while (0) =20 bool nmi_available; +static int unknown_nmi_panic; static struct sse_event *local_nmi_evt; +static struct sse_event *unknown_nmi_evt; +static struct ctl_table_header *unknown_nmi_sysctl_header; static atomic_t local_nmi_arg =3D ATOMIC_INIT(LOCAL_NMI_NONE); =20 bool nmi_support(void) @@ -51,6 +55,35 @@ void send_nmi_mask(cpumask_t *mask, enum local_nmi_type = type) send_nmi_single(cpu, type); } =20 +static int __init setup_unknown_nmi_panic(char *str) +{ + unknown_nmi_panic =3D 1; + return 1; +} +__setup("unknown_nmi_panic", setup_unknown_nmi_panic); + +static const struct ctl_table unknown_nmi_table[] =3D { + { + .procname =3D "unknown_nmi_panic", + .data =3D &unknown_nmi_panic, + .maxlen =3D sizeof(bool), + .mode =3D 0644, + .proc_handler =3D proc_dobool, + }, +}; + +static int unknown_nmi_handler(u32 evt, void *arg, struct pt_regs *regs) +{ + pr_emerg("NMI received for unknown on CPU %d.\n", smp_processor_id()); + + if (unknown_nmi_panic) + nmi_panic(regs, "NMI: Not continuing"); + + pr_emerg("Dazed and confused, but trying to continue\n"); + + return 0; +} + static int local_nmi_handler(u32 evt, void *arg, struct pt_regs *regs) { enum local_nmi_type type =3D atomic_read((atomic_t *)arg); @@ -66,6 +99,35 @@ static int local_nmi_handler(u32 evt, void *arg, struct = pt_regs *regs) return 0; } =20 +static int unknown_nmi_init(void) +{ + int ret; + + unknown_nmi_evt =3D sse_event_register(SBI_SSE_EVENT_LOCAL_UNKNOWN_NMI, 0, + unknown_nmi_handler, NULL); + if (IS_ERR(unknown_nmi_evt)) + return PTR_ERR(unknown_nmi_evt); + + ret =3D sse_event_enable(unknown_nmi_evt); + if (ret) + goto err_unregister; + + unknown_nmi_sysctl_header =3D register_sysctl("kernel", unknown_nmi_table= ); + if (!unknown_nmi_sysctl_header) { + ret =3D -ENOMEM; + goto err_disable; + } + + pr_info("Using SSE for unknown NMI event delivery\n"); + return 0; + +err_disable: + sse_event_disable(unknown_nmi_evt); +err_unregister: + sse_event_unregister(unknown_nmi_evt); + return ret; +} + static int __init local_nmi_init(void) { int ret; @@ -98,6 +160,12 @@ static int __init sse_nmi_init(void) =20 WRITE_ONCE(nmi_available, true); =20 + ret =3D unknown_nmi_init(); + if (ret) { + pr_err("Unknown_nmi_init failed with error %d\n", ret); + return ret; + } + return 0; } =20 --=20 2.39.5