linux-kernel - Re: [External] Re: [PATCH v3 8/8] drivers: firmware: riscv: add unknown nmi support

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Message-Id: <DEPGT7OPYNFW.10L6V344HZE4T@ventanamicro.com>
Date: Thu, 04 Dec 2025 22:26:34 +0900
From: Radim Krčmář <rkrcmar@...tanamicro.com>
To: "yunhui cui" <cuiyunhui@...edance.com>
Cc: <conor@...nel.org>, <paul.walmsley@...ive.com>, <palmer@...belt.com>,
 <aou@...s.berkeley.edu>, <alex@...ti.fr>, <luxu.kernel@...edance.com>,
 <linux-kernel@...r.kernel.org>, <linux-riscv@...ts.infradead.org>,
 <jassisinghbrar@...il.com>, <conor.dooley@...rochip.com>,
 <valentina.fernandezalanis@...rochip.com>, <catalin.marinas@....com>,
 <will@...nel.org>, <maz@...nel.org>, <timothy.hayes@....com>,
 <lpieralisi@...nel.org>, <arnd@...db.de>, <kees@...nel.org>,
 <tglx@...utronix.de>, <viresh.kumar@...aro.org>, <boqun.feng@...il.com>,
 <linux-arm-kernel@...ts.infradead.org>, <cleger@...osinc.com>,
 <atishp@...osinc.com>, <ajones@...tanamicro.com>, "linux-riscv"
 <linux-riscv-bounces@...ts.infradead.org>
Subject: Re: [External] Re: [PATCH v3 8/8] drivers: firmware: riscv: add
 unknown nmi support

2025-12-04T13:18:00+08:00, yunhui cui <cuiyunhui@...edance.com>:
> Hi Radim,
>
> On Thu, Dec 4, 2025 at 12:11 PM Radim Krčmář <rkrcmar@...tanamicro.com> wrote:
>>
>> 2025-11-27T20:53:05+08:00, Yunhui Cui <cuiyunhui@...edance.com>:
>> > 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.
>>
>> Is UNKNOWN_NMI what we expect the watchdog to send?
>
> For reference: As stated in
> https://github.com/riscv-non-isa/riscv-sbi-doc/pull/223, "Generally,
> an external interrupt is used as an Unknown NMI pin, and an Unknown
> NMI event is sent to the SBI firmware by triggering this pin. Then the
> SBI firmware will send SBI_SSE_EVENT_GLOBAL_UNKNOWN_NMI to the
> kernel."
>
> When the Linux system is unresponsive, we can manually trigger it via
> BMC (ipmitool).

Makes sense, thanks, and do we plan to deal with other crash sources?

For example if a watchdog/sysrq triggers a crash, and then gets
interrupted with UNKNOWN_NMI.