linux-kernel - Re: [PATCH] MIPS: reserve the memblock right after the kernel

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Message-ID: <20201110095503.GA10357@alpha.franken.de>
Date:   Tue, 10 Nov 2020 10:55:03 +0100
From:   Thomas Bogendoerfer <tsbogend@...ha.franken.de>
To:     Alexander Sverdlin <alexander.sverdlin@...ia.com>
Cc:     Jiaxun Yang <jiaxun.yang@...goat.com>, linux-mips@...r.kernel.org,
        Paul Burton <paulburton@...nel.org>,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH] MIPS: reserve the memblock right after the kernel

On Mon, Nov 09, 2020 at 11:34:33AM +0100, Alexander Sverdlin wrote:
> Hello Thomas,
> 
> On 07/11/2020 10:40, Thomas Bogendoerfer wrote:
> >> Linux doesn't own the memory immediately after the kernel image. On Octeon
> >> bootloader places a shared structure right close after the kernel _end,
> >> refer to "struct cvmx_bootinfo *octeon_bootinfo" in cavium-octeon/setup.c.
> >>
> >> If check_kernel_sections_mem() rounds the PFNs up, first memblock_alloc()
> >> inside early_init_dt_alloc_memory_arch() <= device_tree_init() returns
> >> memory block overlapping with the above octeon_bootinfo structure, which
> >> is being overwritten afterwards.
> > as this special for Octeon how about added the memblock_reserve
> > in octen specific code ?
> 
> while the shared structure which is being corrupted is indeed Octeon-specific,
> the wrong assumption that the memory right after the kernel can be allocated by memblock
> allocator and re-used somewhere in Linux is in MIPS-generic check_kernel_sections_mem().

ok, I see your point. IMHO this whole check_kernel_sections_mem() should
be removed. IMHO memory adding should only be done my memory detection code.

Could you send a patch, which removes check_kernel_section_mem completly ?

Thomas.

-- 
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea.                                                [ RFC1925, 2.3 ]