linux-kernel - Re: [PATCH v5 09/11] hugetlb: Introduce generic version of huge_ptep_set

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Message-ID: <87muu3hlzc.fsf@concordia.ellerman.id.au>
Date:   Fri, 03 Aug 2018 18:51:03 +1000
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Alex Ghiti <alex@...ti.fr>, linux-mm@...ck.org,
        mike.kravetz@...cle.com, linux@...linux.org.uk,
        catalin.marinas@....com, will.deacon@....com, tony.luck@...el.com,
        fenghua.yu@...el.com, ralf@...ux-mips.org, paul.burton@...s.com,
        jhogan@...nel.org, jejb@...isc-linux.org, deller@....de,
        benh@...nel.crashing.org, ysato@...rs.sourceforge.jp,
        dalias@...c.org, davem@...emloft.net, tglx@...utronix.de,
        mingo@...hat.com, hpa@...or.com, x86@...nel.org, arnd@...db.de,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-ia64@...r.kernel.org, linux-mips@...ux-mips.org,
        linux-parisc@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-sh@...r.kernel.org, sparclinux@...r.kernel.org,
        linux-arch@...r.kernel.org,
        "aneesh.kumar\@linux.ibm.com" <aneesh.kumar@...ux.ibm.com>
Subject: Re: [PATCH v5 09/11] hugetlb: Introduce generic version of huge_ptep_set_wrprotect

Hi Alex,

Sorry missed your previous mail.

Alex Ghiti <alex@...ti.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