linux-kernel - Re: [PATCH v5 02/27] mm, cma: support multiple contiguous ranges, if requested

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Message-ID: <CAPTztWaAmG2L7L7x0boGG2aCNosJ8GHU=GiAQP-2nuP3k2650A@mail.gmail.com>
Date: Mon, 7 Apr 2025 08:52:41 -0700
From: Frank van der Linden <fvdl@...gle.com>
To: Geert Uytterhoeven <geert@...ux-m68k.org>
Cc: akpm@...ux-foundation.org, muchun.song@...ux.dev, linux-mm@...ck.org, 
	linux-kernel@...r.kernel.org, yuzhao@...gle.com, usamaarif642@...il.com, 
	joao.m.martins@...cle.com, roman.gushchin@...ux.dev, ziy@...dia.com, 
	david@...hat.com, Arnd Bergmann <arnd@...db.de>, 
	Linux-Renesas <linux-renesas-soc@...r.kernel.org>, 
	Linux ARM <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v5 02/27] mm, cma: support multiple contiguous ranges, if requested

On Mon, Apr 7, 2025 at 4:50 AM Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
>
> Thanks for your patch, which is now commit c009da4258f9885c
> ("mm, cma: support multiple contiguous ranges, if requested")
> in v6.15-rc1.
>
> After this patch, the printed base address becomes zero on several
> Renesas arm32/arm64 platforms:
>
>   - Koelsch (R-Car M2-W):
>
>       -cma: Reserved 64 MiB at 0x7c000000 on node -1
>       +cma: Reserved 64 MiB at 0x00000000
>
>    - Salvator-XS (R-Car H3 ES2.0):
>
>       -cma: Reserved 128 MiB at 0x0000000078000000 on node -1
>       +cma: Reserved 128 MiB at 0x0000000000000000
>
>   - Gray Hawk Single (R-Car V4H):
>
>       -cma: Reserved 128 MiB at 0x00000000b8000000 on node -1
>       +cma: Reserved 128 MiB at 0x0000000000000000
>
> None of these have actual RAM at address zero.  As I haven't noticed
> any other impact on system operation, I do not know if this is purely
> a cosmetic issue, or if it can cause real problems.
>
> Thanks!
>
> Gr{oetje,eeting}s,
>
>                         Geert

Hi Geert,

Thanks for the report! This is just a reporting issue with my change,
it's working fine otherwise. I refactored the code slightly, and the
!fixed && !multi case will now report base 0, because it doesn't 'see'
the actual allocated base. Let me send a follow-up patch.

Thanks again,

- Frank