linux-kernel - Re: [RFT PATCH] MIPS: Octeon: drop dependency on CONFIG_HOLES_IN

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Date:   Tue, 11 May 2021 22:40:52 +0200
From:   Thomas Bogendoerfer <tsbogend@...ha.franken.de>
To:     Mike Rapoport <rppt@...nel.org>
Cc:     linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org,
        Mike Rapoport <rppt@...ux.ibm.com>
Subject: Re: [RFT PATCH] MIPS: Octeon: drop dependency on CONFIG_HOLES_IN_ZONE

On Sun, Apr 18, 2021 at 12:35:12PM +0300, Mike Rapoport wrote:
> From: Mike Rapoport <rppt@...ux.ibm.com>
> 
> CAVIUM_OCTEON_SOC configuration selects HOLES_IN_ZONE option to cope with
> memory crashes that were happening in 2011.
> 
> This option effectively aliases pfn_valid_within() to pfn_valid() when
> enabled and hardwires it to 1 when disabled. The check for
> pfn_valid_within() is only relevant in case the memory map may have holes
> or undefined struct page instances inside MAX_ORDER chunks.
> 
> Since 2011 memory management initialization in general and memory map
> initialization particularly became much more robust so the check for
> pfn_valid_within() is not required on Octeon even despite its, hmm, unusual
> memory setup.
> 
> Remove the selection of HOLES_IN_ZONE by CAVIUM_OCTEON_SOC and drop the
> HOLES_IN_ZONE configuration option entirely as Octeon was the only MIPS
> platform to use it.
> 
> Signed-off-by: Mike Rapoport <rppt@...ux.ibm.com>
> ---
> 
> Hi,
> 
> I've tried to find why Octeon needed CONFIG_HOLES_IN_ZONE in the first
> place, but there is nothing except the changelog in commit 465aaed0030b
> ("MIPS: Octeon: Select CONFIG_HOLES_IN_ZONE"):
> 
>   Current Octeon systems do in fact have holes in their memory zones.
>   We need to select HOLES_IN_ZONE. If we do not, some memory configurations
>   will result in crashes at boot time
> 
> Since then there were too many changes around memory management
> initialization both in the generic mm and on the MIPS side to track what
> exactly could case the crashes.
> 
> I'm pretty confident that HOLES_IN_ZONE is not required for Octeon systems
> anymore and can be removed.
> 
> I'd really appreciate if somebody with access to an Octeon system could
> test this patch.
> 
>  arch/mips/Kconfig | 4 ----
>  1 file changed, 4 deletions(-)

applied to mips-next.

Thomas.

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