linux-kernel - Re: [External] [PATCH v7 2/5] riscv: add support for SBI Supervisor Software Events extension

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Message-ID: <2b4cd5a6-98f8-4ec6-bdac-c6c7dae84049@rivosinc.com>
Date: Mon, 27 Oct 2025 14:29:29 +0100
From: Clément Léger <cleger@...osinc.com>
To: Xu Lu <luxu.kernel@...edance.com>
Cc: Paul Walmsley <paul.walmsley@...ive.com>,
 Palmer Dabbelt <palmer@...belt.com>, linux-riscv@...ts.infradead.org,
 linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 Himanshu Chauhan <hchauhan@...tanamicro.com>,
 Anup Patel <apatel@...tanamicro.com>, Atish Patra <atishp@...shpatra.org>,
 Björn Töpel <bjorn@...osinc.com>,
 Yunhui Cui <cuiyunhui@...edance.com>
Subject: Re: [External] [PATCH v7 2/5] riscv: add support for SBI Supervisor
 Software Events extension



On 10/27/25 13:00, Xu Lu wrote:
>> +void do_sse(struct sse_event_arch_data *arch_evt, struct pt_regs *regs)
>> +{
>> +       nmi_enter();
>> +
>> +       /* Retrieve missing GPRs from SBI */
>> +       sbi_ecall(SBI_EXT_SSE, SBI_SSE_EVENT_ATTR_READ, arch_evt->evt_id,
>> +                 SBI_SSE_ATTR_INTERRUPTED_A6,
>> +                 (SBI_SSE_ATTR_INTERRUPTED_A7 - SBI_SSE_ATTR_INTERRUPTED_A6) + 1,
>> +                 arch_evt->interrupted_phys, 0, 0);
>> +
>> +       memcpy(&regs->a6, &arch_evt->interrupted, sizeof(arch_evt->interrupted));
>> +
>> +       sse_handle_event(arch_evt, regs);
>> +
>> +       /*
>> +        * The SSE delivery path does not uses the "standard" exception path
>> +        * (see sse_entry.S) and does not process any pending signal/softirqs
>> +        * due to being similar to a NMI.
>> +        * Some drivers (PMU, RAS) enqueue pending work that needs to be handled
>> +        * as soon as possible by bottom halves. For that purpose, set the SIP
>> +        * software interrupt pending bit which will force a software interrupt
>> +        * to be serviced once interrupts are reenabled in the interrupted
>> +        * context if they were masked or directly if unmasked.
>> +        */
>> +       csr_set(CSR_IP, IE_SIE);
> IE_SIE may not always be enabled in CSR_IE(for example when we disable
> CONFIG_ACLINT_SSWI and use imsic for ipi). Maybe we should send ipi to
> the current cpu here.

Hi Xu,

Indeed, that's a good catch. Sending an IPI will be more generic.

Thanks,

Clément

> 
> Best regards,
> Xu Lu