linux-kernel - Re: [PATCH RFC] mm/memblock: Fix reserve_mem allocation overlapping KHO scratch regions

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Message-ID: <aS06sCvwSkcn1XcE@kernel.org>
Date: Mon, 1 Dec 2025 08:50:24 +0200
From: Mike Rapoport <rppt@...nel.org>
To: Swaraj Gaikwad <swarajgaikwad1925@...il.com>
Cc: akpm@...ux-foundation.org, david.hunter.linux@...il.com,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	skhan@...uxfoundation.org
Subject: Re: [PATCH RFC] mm/memblock: Fix reserve_mem allocation overlapping
 KHO scratch regions

Hi Swaraj,

On Sun, Nov 30, 2025 at 09:15:39PM +0000, Swaraj Gaikwad wrote:
> Hi Mike,
> 
> Thanks for the feedback.
> 
> This patch was sent as an RFC because I wanted to confirm whether the
> overall approach is acceptable before preparing a fully tested version.
> I will send a properly tested patch once I get confirmation that this
> direction makes sense.

I didn't look into the details, but I think what you propose won't work.
The first kernel allocates KHO scratch after parsing reserve_mem and the
second kernel allocates everything from KHO scratch at the time
early_params are parsed.
 
> I’m reviewing how reserve_mem= paths are exercised so I can build an
> appropriate test setup. Any guidance on recommended testing for this
> area is appreciated.

In general to test changes to memblock and other early code I use qemu and
some scripts around it.
 
> Thanks,
> Swaraj

-- 
Sincerely yours,
Mike.