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

[Radim Krčmář]

2025-12-04T13:18:00+08:00, yunhui cui <cuiyunhui at bytedance.com>:
> Hi Radim,
>
> On Thu, Dec 4, 2025 at 12:11 PM Radim Krčmář <rkrcmar at ventanamicro.com> wrote:
>>
>> 2025-11-27T20:53:05+08:00, Yunhui Cui <cuiyunhui at bytedance.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.