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From: Michael Ellerman <mpe@ellerman.id.au>
Subject: Re: [PATCH v5 09/11] hugetlb: Introduce generic version of huge_ptep_set_wrprotect
In-Reply-To: <90bf556f-144d-24b8-d2f6-70fee4a30559@ghiti.fr>
References: <20180731060155.16915-1-alex@ghiti.fr> <20180731060155.16915-10-alex@ghiti.fr> <87h8kfhg7o.fsf@concordia.ellerman.id.au> <6acb1389-6998-bafb-cf69-174fd522c04c@ghiti.fr> <90bf556f-144d-24b8-d2f6-70fee4a30559@ghiti.fr>
Date: Fri, 03 Aug 2018 18:51:03 +1000
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To: Alex Ghiti <alex@ghiti.fr>, linux-mm@kvack.org, mike.kravetz@oracle.com, linux@armlinux.org.uk, catalin.marinas@arm.com, will.deacon@arm.com, tony.luck@intel.com, fenghua.yu@intel.com, ralf@linux-mips.org, paul.burton@mips.com, jhogan@kernel.org, jejb@parisc-linux.org, deller@gmx.de, benh@kernel.crashing.org, ysato@users.sourceforge.jp, dalias@libc.org, davem@davemloft.net, tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, x86@kernel.org, arnd@arndb.de, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-ia64@vger.kernel.org, linux-mips@linux-mips.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, linux-arch@vger.kernel.org, "aneesh.kumar@linux.ibm.com" <aneesh.kumar@linux.ibm.com>

Hi Alex,

Sorry missed your previous mail.

Alex Ghiti <alex@ghiti.fr> writes:
> Ok, I tried every defconfig available:
>
> - for the nohash/32, I found that I could use mpc885_ads_defconfig and I 
> activated HUGETLBFS.
> I removed the definition of huge_ptep_set_wrprotect from 
> nohash/32/pgtable.h, add an #error in
> include/asm-generic/hugetlb.h right before the generic definition of 
> huge_ptep_set_wrprotect,
> and fell onto it at compile-time:
> => I'm pretty confident then that removing the definition of 
> huge_ptep_set_wrprotect does not
> break anythingin this case.

Thanks, that sounds good.

> - regardind book3s/32, I did not find any defconfig with 
> CONFIG_PPC_BOOK3S_32, CONFIG_PPC32
> allowing to enable huge page support (ie CONFIG_SYS_SUPPORTS_HUGETLBFS)
> => Do you have a defconfig that would allow me to try the same as above ?

I think you're right, it's dead code AFAICS.

We have:

config PPC_BOOK3S_64
        ...
	select SYS_SUPPORTS_HUGETLBFS

config PPC_FSL_BOOK3E
        ...
	select SYS_SUPPORTS_HUGETLBFS if PHYS_64BIT || PPC64

config PPC_8xx
	...
	select SYS_SUPPORTS_HUGETLBFS


So we can't ever enable HUGETLBFS for Book3S 32.

Presumably the code got copied when we split the headers apart.

So I think you can just ignore that one, and we'll delete it.

cheers