From: anshuman.khandual@arm.com (Anshuman Khandual)
To: linux-snps-arc@lists.infradead.org
Subject: [PATCH V2 2/2] mm/pgtable/debug: Add test validating architecture page table helpers
Date: Fri, 20 Sep 2019 09:36:12 +0530 [thread overview]
Message-ID: <5a6045af-bcfb-12c2-0f4a-3b49a905ec4d@arm.com> (raw)
In-Reply-To: <20190918202243.37e709df@thinkpad>
On 09/18/2019 11:52 PM, Gerald Schaefer wrote:
> 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.
Like Christophe mentioned earlier on the other thread, we will convert
all __PGTABLE_PXX_FOLDED checks as mm_pxx_folded() but looks like
ARCH_HAS_[4 and 5]LEVEL_HACK macros will still be around. Will respin
the series with all agreed upon changes first and probably we can then
discuss pending issues from there.
>
> 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.
Atleast p4d_clear/populate_tests() tests will be taken care.
>
> 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?
Agreed, it seems better to do the check inside p4d/pud_free() functions.
next prev parent reply other threads:[~2019-09-20 4:06 UTC|newest]
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 page table helpers 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
2019-09-20 4:06 ` Anshuman Khandual [this message]
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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