linux-kernel - Re: [PATCH] RISC-V: cpu-hotplug fix

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Message-ID: <7bc8eb67-0a48-1756-c907-dae7751b4c98@kernel.org>
Date: Wed, 8 Oct 2025 11:50:53 -0600 (MDT)
From: Paul Walmsley <pjw@...nel.org>
To: Danil Skrebenkov <danil.skrebenkov@...udbear.ru>
cc: pjw@...nel.org, Paul Walmsley <paul.walmsley@...ive.com>, 
    Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>, 
    Alexandre Ghiti <alex@...ti.fr>, Charlie Jenkins <charlie@...osinc.com>, 
    WangYuli <wangyuli@...ontech.com>, linux-riscv@...ts.infradead.org, 
    linux-kernel@...r.kernel.org
Subject: Re: [PATCH] RISC-V: cpu-hotplug fix

On Fri, 19 Sep 2025, Danil Skrebenkov wrote:

> openSBI v1.7 adds harts checks for ipi operations. Especially it
> adds comparison between hmask passed as an argument from linux
> and mask of online harts (from openSBI side). If they don't
> fit each other the error occurs.
> 
> When cpu is offline, cpu_online_mask is explicitly cleared in
> __cpu_disable. However, there is no explicit clearing of
> mm_cpumask. mm_cpumask is used for rfence operations that
> call openSBI RFENCE extension which uses ipi to remote harts.
> If hart is offline there may be error if mask of linux is not
> as mask of online harts in openSBI.
> 
> this patch adds explicit clearing of mm_cpumask for offline hart.
> 
> Signed-off-by: Danil Skrebenkov <danil.skrebenkov@...udbear.ru>

Thanks, queued for early v6.18-rc after cleaning up the subject line to be 
more descriptive:

"RISC-V: clear hot-unplugged cores from all task mm_cpumasks to avoid 
rfence errors"


- Paul