linux-kernel - Re: [RFC v2 7/9] x86/mm: Introduce Remote Action Request

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Message-ID: <87plg1rdf3.ffs@tglx>
Date: Wed, 21 May 2025 21:06:56 +0200
From: Thomas Gleixner <tglx@...utronix.de>
To: Dave Hansen <dave.hansen@...el.com>, Rik van Riel <riel@...riel.com>,
 linux-kernel@...r.kernel.org
Cc: linux-mm@...ck.org, x86@...nel.org, kernel-team@...a.com,
 dave.hansen@...ux.intel.com, luto@...nel.org, peterz@...radead.org,
 mingo@...hat.com, bp@...en8.de, hpa@...or.com, nadav.amit@...il.com,
 Yu-cheng Yu <yu-cheng.yu@...el.com>
Subject: Re: [RFC v2 7/9] x86/mm: Introduce Remote Action Request

On Wed, May 21 2025 at 09:38, Dave Hansen wrote:
> On 5/19/25 18:02, Rik van Riel wrote:
>> +/*
>> + * This is a modified version of smp_call_function_many() of kernel/smp.c,
>> + * without a function pointer, because the RAR handler is the ucode.
>> + */
>
> It doesn't look _that_ much like smp_call_function_many(). I don't see
> much that can be consolidated.

It does not look like it because it has a gazillion of function
arguments, which can all be packed into a data structure, i.e. the
function argument of smp_call_function_many().

There is zero justification to reinvent the wheel and create another
source of hard to debug problems.

IMNSHO it's absolutely not rocket science to reuse
smp_call_function_many() for this, but I might be missing something as
always and I'm happy to be enlightenend.

Just for the record: The changelog contains an utter void of information
why this modified version of well established common code is required
and desired.

Thanks,

        tglx