linux-kernel - Re: [PATCH V2 2/2] mm/pgtable/debug: Add test validating architecture page table helpers

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Date:   Fri, 13 Sep 2019 12:01:00 +0200
From:   Christophe Leroy <christophe.leroy@....fr>
To:     Anshuman Khandual <anshuman.khandual@....com>, linux-mm@...ck.org
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Dan Williams <dan.j.williams@...el.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Michal Hocko <mhocko@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Mark Brown <broonie@...nel.org>,
        Steven Price <Steven.Price@....com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Kees Cook <keescook@...omium.org>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        Matthew Wilcox <willy@...radead.org>,
        Sri Krishna chowdary <schowdary@...dia.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Russell King - ARM Linux <linux@...linux.org.uk>,
        Michael Ellerman <mpe@...erman.id.au>,
        Paul Mackerras <paulus@...ba.org>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        "David S. Miller" <davem@...emloft.net>,
        Vineet Gupta <vgupta@...opsys.com>,
        James Hogan <jhogan@...nel.org>,
        Paul Burton <paul.burton@...s.com>,
        Ralf Baechle <ralf@...ux-mips.org>,
        "Kirill A . Shutemov" <kirill@...temov.name>,
        Gerald Schaefer <gerald.schaefer@...ibm.com>,
        linux-snps-arc@...ts.infradead.org, linux-mips@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-ia64@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-s390@...r.kernel.org,
        linux-sh@...r.kernel.org, sparclinux@...r.kernel.org,
        x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2 2/2] mm/pgtable/debug: Add test validating architecture
 page table helpers



Le 13/09/2019 à 11:02, Anshuman Khandual a écrit :
> 
>>> +#if !defined(__PAGETABLE_PMD_FOLDED) && !defined(__ARCH_HAS_4LEVEL_HACK)
>>
>> #ifdefs have to be avoided as much as possible, see below
> 
> Yeah but it has been bit difficult to avoid all these $ifdef because of the
> availability (or lack of it) for all these pgtable helpers in various config
> combinations on all platforms.

As far as I can see these pgtable helpers should exist everywhere at 
least via asm-generic/ files.

Can you spot a particular config which fails ?

> 
>>

[...]

>>> +#if !defined(__PAGETABLE_PUD_FOLDED) && !defined(__ARCH_HAS_5LEVEL_HACK)
>>
>> The same can be done here.
> 
> IIRC not only the page table helpers but there are data types (pxx_t) which
> were not present on various configs and these wrappers help prevent build
> failures. Any ways will try and see if this can be improved further. But
> meanwhile if you have some suggestions, please do let me know.

pgt_t and pmd_t are everywhere I guess.
then pud_t and p4d_t have fallbacks in asm-generic files.

So it shouldn't be an issue. Maybe if a couple of arches miss them, the 
best would be to fix the arches, since that's the purpose of your 
testsuite isn't it ?


Christophe