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From: Gerald Schaefer <gerald.schaefer@de.ibm.com>
To: Christophe Leroy <christophe.leroy@c-s.fr>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>,
	linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
	Vlastimil Babka <vbabka@suse.cz>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Mike Rapoport <rppt@linux.vnet.ibm.com>,
	Jason Gunthorpe <jgg@ziepe.ca>,
	Dan Williams <dan.j.williams@intel.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Michal Hocko <mhocko@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Mark Brown <broonie@kernel.org>,
	Steven Price <Steven.Price@arm.com>,
	Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	Masahiro Yamada <yamada.masahiro@socionext.com>,
	Kees Cook <keescook@chromium.org>,
	Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
	Matthew Wilcox <willy@infradead.org>,
	Sri Krishna chowdary <schowdary@nvidia.com>,
	Dave Hansen <dave.hansen@intel.com>,
	Russell King - ARM Linux <linux@armlinux.org.uk>,
	Michael Ellerman <mpe@ellerman.id.au>,
	Paul Mackerras <paulus@samba.org>,
	Martin Schwidefsky <schwidefsky@de.ibm.com>,
	Heiko Carstens <heiko.carstens@de.ibm.com>,
	"David S. Miller" <davem@davemloft.net>,
	Vineet Gupta <vgupta@synopsys.com>,
	James Hogan <jhogan@kernel.org>,
	Paul Burton <paul.burton@mips.com>,
	Ralf Baechle <ralf@linux-mips.org>,
	"Kirill A . Shutemov" <kirill@shutemov.name>,
	linux-snps-arc@lists.infradead.org, linux-mips@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org, linux-ia64@vger.kernel.org,
	linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org,
	linux-sh@vger.kernel.org, sparclinux@vger.kernel.org,
	x86@kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH V2 2/2] mm/pgtable/debug: Add test validating architecture page table helpers
Date: Wed, 18 Sep 2019 20:22:43 +0200
Message-ID: <20190918202243.37e709df@thinkpad> (raw)
In-Reply-To: <64504101-d9dd-f273-02f9-e9a8b178eecc@c-s.fr>

On Wed, 18 Sep 2019 18:26:03 +0200
Christophe Leroy <christophe.leroy@c-s.fr> wrote:

[..] 
> My suggestion was not to completely drop the #ifdef but to do like you 
> did in pgd_clear_tests() for instance, ie to add the following test on 
> top of the function:
> 
> 	if (mm_pud_folded(mm) || is_defined(__ARCH_HAS_5LEVEL_HACK))
> 		return;
> 

Ah, very nice, this would also fix the remaining issues for s390. Since
we have dynamic page table folding, neither __PAGETABLE_PXX_FOLDED nor
__ARCH_HAS_XLEVEL_HACK is defined, but mm_pxx_folded() will work.

mm_alloc() returns with a 3-level page table by default on s390, so we
will run into issues in p4d_clear/populate_tests(), and also at the end
with p4d/pud_free() (double free).

So, adding the mm_pud_folded() check to p4d_clear/populate_tests(),
and also adding mm_p4d/pud_folded() checks at the end before calling
p4d/pud_free(), would make it all work on s390.

BTW, regarding p4d/pud_free(), I'm not sure if we should rather check
the folding inside our s390 functions, similar to how we do it for
p4d/pud_free_tlb(), instead of relying on not being called for folded
p4d/pud. So far, I see no problem with this behavior, all callers of
p4d/pud_free() should be fine because of our folding check within
p4d/pud_present/none(). But that doesn't mean that it is correct not
to check for the folding inside p4d/pud_free(). At least, with this
test module we do now have a caller of p4d/pud_free() on potentially
folded entries, so instead of adding pxx_folded() checks to this
test module, we could add them to our p4d/pud_free() functions.
Any thoughts on this?

Regards,
Gerald


  reply index

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-12  6:02 [PATCH V2 0/2] mm/debug: Add tests for architecture exported " Anshuman Khandual
2019-09-12  6:02 ` [PATCH V2 2/2] mm/pgtable/debug: Add test validating architecture " Anshuman Khandual
2019-09-12 11:00   ` Kirill A. Shutemov
2019-09-12 12:09     ` Anshuman Khandual
2019-09-12 15:00   ` Christophe Leroy
2019-09-12 15:36     ` Christophe Leroy
2019-09-12 15:52       ` Christophe Leroy
2019-09-13  6:30         ` Christophe Leroy
2019-09-12 17:14   ` Christophe Leroy
2019-09-13  6:23     ` [PATCH] mm/pgtable/debug: Fix " Christophe Leroy
2019-09-13  6:58       ` Anshuman Khandual
2019-09-13  7:03         ` Christophe Leroy
2019-09-13  7:11           ` Christophe Leroy
2019-09-13  8:42             ` Anshuman Khandual
2019-09-13  8:51               ` Kirill A. Shutemov
2019-09-18  7:32       ` Anshuman Khandual
2019-09-19  5:44         ` Christophe Leroy
2019-09-13  9:02     ` [PATCH V2 2/2] mm/pgtable/debug: Add " Anshuman Khandual
2019-09-13  9:13       ` Kirill A. Shutemov
2019-09-13 10:01       ` Christophe Leroy
2019-09-18  5:04         ` Anshuman Khandual
2019-09-18 16:26           ` Christophe Leroy
2019-09-18 18:22             ` Gerald Schaefer [this message]
2019-09-20  4:06               ` Anshuman Khandual
2019-09-19  4:56             ` Anshuman Khandual
2019-09-19  5:41               ` Christophe Leroy
2019-09-12 14:42 ` [PATCH V2 0/2] mm/debug: Add tests for architecture exported " Christophe Leroy
2019-09-13  6:24   ` Anshuman Khandual
2019-09-13  6:32     ` Christophe Leroy

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