linux-kernel - Re: [PATCH 3/3] riscv: crash: use NMI to stop the CPU

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Message-Id: <DDTYKLFUE3M0.17GD0S4OSQG16@ventanamicro.com>
Date: Tue, 28 Oct 2025 13:36:20 +0100
From: Radim Krčmář <rkrcmar@...tanamicro.com>
To: "Conor Dooley" <conor@...nel.org>, "Yunhui Cui"
 <cuiyunhui@...edance.com>
Cc: <paul.walmsley@...ive.com>, <palmer@...belt.com>,
 <aou@...s.berkeley.edu>, <alex@...ti.fr>, <luxu.kernel@...edance.com>,
 <atishp@...osinc.com>, <cleger@...osinc.com>, <ajones@...tanamicro.com>,
 <apatel@...tanamicro.com>, <linux-kernel@...r.kernel.org>,
 <linux-riscv@...ts.infradead.org>, <songshuaishuai@...ylab.org>,
 <bjorn@...osinc.com>, <charlie@...osinc.com>, <masahiroy@...nel.org>,
 <valentina.fernandezalanis@...rochip.com>, <jassisinghbrar@...il.com>,
 <conor.dooley@...rochip.com>, "linux-riscv"
 <linux-riscv-bounces@...ts.infradead.org>
Subject: Re: [PATCH 3/3] riscv: crash: use NMI to stop the CPU

2025-10-28T10:42:12+00:00, Conor Dooley <conor@...nel.org>:
> On Mon, Oct 27, 2025 at 09:34:31PM +0800, Yunhui Cui wrote:
>> NMI is more robust than IPI for stopping CPUs during crashes,
>> especially with interrupts disabled. Add SBI_SSE_EVENT_LOCAL_CRASH_NMI
>> eventid to implement NMI for stopping CPUs.
>> 
>> Signed-off-by: Yunhui Cui <cuiyunhui@...edance.com>
>> ---
>> diff --git a/arch/riscv/include/asm/sbi.h b/arch/riscv/include/asm/sbi.h
>> @@ -487,6 +487,7 @@ enum sbi_sse_attr_id {
>>  #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_LOCAL_CRASH_NMI		0xffff0002

This event isn't defined in the SBI pull request.

I assume it's a pure software event that the platform shouldn't inject.
If we want to reserve more events for software use, why not make them
generic, like SBI_SSE_EVENT_LOCAL_SOFTWARE_INJECTED?

Thanks.