linux-kernel - Re: [PATCH v2 10/13] arch, mm: set high_memory in free_area

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Message-Id: <20250402151940.145c3bf65387b10735fe5c4f@linux-foundation.org>
Date: Wed, 2 Apr 2025 15:19:40 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: Mike Rapoport <rppt@...nel.org>
Cc: Thomas Weißschuh <thomas.weissschuh@...utronix.de>,
 Dave Hansen <dave.hansen@...ux.intel.com>, Andy Lutomirski
 <luto@...nel.org>, Ard Biesheuvel <ardb@...nel.org>, Arnd Bergmann
 <arnd@...db.de>, Borislav Petkov <bp@...en8.de>, "David S. Miller"
 <davem@...emloft.net>, Geert Uytterhoeven <geert@...ux-m68k.org>, Ingo
 Molnar <mingo@...hat.com>, Peter Zijlstra <peterz@...radead.org>, Thomas
 Gleixner <tglx@...utronix.de>, linux-kernel@...r.kernel.org,
 linux-arch@...r.kernel.org, linux-mm@...ck.org, x86@...nel.org, Naresh
 Kamboju <naresh.kamboju@...aro.org>, lkft-triage@...ts.linaro.org, Linux
 Regressions <regressions@...ts.linux.dev>
Subject: Re: [PATCH v2 10/13] arch, mm: set high_memory in free_area_init()

On Wed, 2 Apr 2025 23:18:55 +0300 Mike Rapoport <rppt@...nel.org> wrote:

> The proper fix is
> 
> diff --git a/mm/memblock.c b/mm/memblock.c
> index 64ae678cd1d1..d7ff8dfe5f88 100644
> --- a/mm/memblock.c
> +++ b/mm/memblock.c
> @@ -2166,6 +2166,9 @@ static unsigned long __init __free_memory_core(phys_addr_t start,
>  	unsigned long start_pfn = PFN_UP(start);
>  	unsigned long end_pfn = PFN_DOWN(end);
>  
> +	if (!IS_ENABLED(CONFIG_HIGHMEM) && end_pfn > max_low_pfn)
> +		end_pfn = max_low_pfn;
> +
>  	if (start_pfn >= end_pfn)
>  		return 0;
> 
> I've sent it along with the fix for x86 [1] (commit 7790c9c9265e
> ("memblock: don't release high memory to page allocator when HIGHMEM is
> off") in mm-unstable), but for some reason it didn't make it to the Linus
> tree :/
> 
> @Andrew, are you going to send it to Linus or you prefer if I take it via
> memblock tree? 
> 
> [1] https://lore.kernel.org/all/20250325114928.1791109-3-rppt@kernel.org/

That fix is now in mm-stable for a second round of merge window
material.  I'll send that off to Linus later today.