[PATCH 1/3] drivers: firmware: riscv: add SSE NMI support

[Yunhui Cui <cuiyunhui@bytedance.com>]

Add support for handling Non-Maskable Interrupts (NMIs) through the
RISC-V Supervisor Software Events (SSE) framework. Since each NMI
type(e.g., unknown NMI, etc.) requires a distinct SSE event, a newfile
sse_nmi.c is introduced to manage their registration and enabling.

Signed-off-by: Yunhui Cui <cuiyunhui@bytedance.com>
---
 MAINTAINERS                      |  7 +++
 arch/riscv/include/asm/sbi.h     |  1 +
 drivers/firmware/riscv/Kconfig   | 10 ++++
 drivers/firmware/riscv/Makefile  |  1 +
 drivers/firmware/riscv/sse_nmi.c | 81 ++++++++++++++++++++++++++++++++
 5 files changed, 100 insertions(+)
 create mode 100644 drivers/firmware/riscv/sse_nmi.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 8bf5416953f45..6df6cbec4d85d 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -22057,6 +22057,13 @@ S:	Maintained
 F:	drivers/firmware/riscv/riscv_sse.c
 F:	include/linux/riscv_sse.h
 
+RISC-V SSE NMI SUPPORT
+M:	Yunhui Cui <cuiyunhui@bytedance.com>
+R:	Xu Lu <luxu.kernel@bytedance.com>
+L:	linux-riscv@lists.infradead.org
+S:	Maintained
+F:	drivers/firmware/riscv/sse_nmi.c
+
 RISC-V THEAD SoC SUPPORT
 M:	Drew Fustini <fustini@kernel.org>
 M:	Guo Ren <guoren@kernel.org>
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
 
 #define SBI_SSE_EVENT_PLATFORM		BIT(14)
diff --git a/drivers/firmware/riscv/Kconfig b/drivers/firmware/riscv/Kconfig
index ed5b663ac5f91..fd16b4c43cf01 100644
--- a/drivers/firmware/riscv/Kconfig
+++ b/drivers/firmware/riscv/Kconfig
@@ -12,4 +12,14 @@ config RISCV_SBI_SSE
 	  this option provides support to register callbacks on specific SSE
 	  events.
 
+config RISCV_SSE_NMI
+	bool "Enable SBI Supervisor Software Events NMI support"
+	depends on RISCV_SBI_SSE
+	default y
+	help
+	  This option enables support for delivering Non-Maskable Interrupt
+	  (NMI) notifications through the Supervisor Software Events (SSE)
+	  framework. When enabled, the system supports some common NMI features
+	  such as unknown NMI handling.
+
 endmenu
diff --git a/drivers/firmware/riscv/Makefile b/drivers/firmware/riscv/Makefile
index c8795d4bbb2ea..ecf2b31935d9c 100644
--- a/drivers/firmware/riscv/Makefile
+++ b/drivers/firmware/riscv/Makefile
@@ -1,3 +1,4 @@
 # SPDX-License-Identifier: GPL-2.0
 
 obj-$(CONFIG_RISCV_SBI_SSE)		+= riscv_sbi_sse.o
+obj-$(CONFIG_RISCV_SSE_NMI)		+= sse_nmi.o
diff --git a/drivers/firmware/riscv/sse_nmi.c b/drivers/firmware/riscv/sse_nmi.c
new file mode 100644
index 0000000000000..2c1eaea2bbabc
--- /dev/null
+++ b/drivers/firmware/riscv/sse_nmi.c
@@ -0,0 +1,81 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#define pr_fmt(fmt) "SSE NMI: " fmt
+
+#include <linux/nmi.h>
+#include <linux/riscv_sbi_sse.h>
+#include <linux/sysctl.h>
+
+#include <asm/irq_regs.h>
+#include <asm/sbi.h>
+
+int unknown_nmi_panic;
+static struct sse_event *unknown_nmi_evt;
+static struct ctl_table_header *unknown_nmi_sysctl_header;
+
+static int __init setup_unknown_nmi_panic(char *str)
+{
+	unknown_nmi_panic = 1;
+	return 1;
+}
+__setup("unknown_nmi_panic", setup_unknown_nmi_panic);
+
+const struct ctl_table unknown_nmi_table[] = {
+	{
+		.procname	= "unknown_nmi_panic",
+		.data		= &unknown_nmi_panic,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= SYSCTL_ZERO,
+		.extra2		= SYSCTL_ONE,
+	},
+};
+
+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 unknown_nmi_init(void)
+{
+	int ret;
+
+	unknown_nmi_evt = 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 = sse_event_enable(unknown_nmi_evt);
+	if (ret)
+		goto err_unregister;
+
+	unknown_nmi_sysctl_header = register_sysctl("kernel", unknown_nmi_table);
+	if (!unknown_nmi_sysctl_header) {
+		ret = -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 sse_nmi_init(void)
+{
+	return unknown_nmi_init();
+}
+
+late_initcall(sse_nmi_init);
-- 
2.39.5


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