From: Vlastimil Babka <vbabka@suse.cz>
To: Will Deacon <will.deacon@arm.com>,
"Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Andrew Morton <akpm@linux-foundation.org>,
Vineet Gupta <vgupta@synopsys.com>,
Russell King <linux@armlinux.org.uk>,
Catalin Marinas <catalin.marinas@arm.com>,
Ralf Baechle <ralf@linux-mips.org>,
"David S. Miller" <davem@davemloft.net>,
Heiko Carstens <heiko.carstens@de.ibm.com>,
Martin Schwidefsky <schwidefsky@de.ibm.com>,
Andrea Arcangeli <aarcange@redhat.com>,
linux-arch@vger.kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, mark.rutland@arm.com
Subject: Re: [HELP-NEEDED, PATCH 0/3] Do not loose dirty bit on THP pages
Date: Wed, 14 Jun 2017 19:00:47 +0200 [thread overview]
Message-ID: <d589ad0a-d5d4-927a-597c-4b094285d4b1@suse.cz> (raw)
In-Reply-To: <20170614165513.GD17632@arm.com>
On 06/14/2017 06:55 PM, Will Deacon wrote:
>>
>> May be we should relook at pmd PTE udpate interface. We really need an
>> interface that can update pmd entries such that we don't clear it in
>> between. IMHO, we can avoid the pmdp_invalidate() completely, if we can
>> switch from a pmd PTE entry to a pointer to PTE page (pgtable_t). We also
>> need this interface to avoid the madvise race fixed by
>
> There's a good chance I'm not following your suggestion here, but it's
> probably worth me pointing out that swizzling a page table entry from a
> block mapping (e.g. a huge page mapped at the PMD level) to a table entry
> (e.g. a pointer to a page of PTEs) can lead to all sorts of horrible
> problems on ARM, including amalgamation of TLB entries and fatal aborts.
AFAIK some AMD x86_64 CPU's had the same problem and generated MCE's,
and on Intel there are some restrictions when you can do that. See the
large comment in __split_huge_pmd_locked().
> So we really need to go via an invalid entry, with appropriate TLB
> invalidation before installing the new entry.
>
> Will
>
next prev parent reply other threads:[~2017-06-14 17:01 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-14 13:51 [HELP-NEEDED, PATCH 0/3] Do not loose dirty bit on THP pages Kirill A. Shutemov
2017-06-14 13:51 ` [PATCH 1/3] x86/mm: Provide pmdp_mknotpresent() helper Kirill A. Shutemov
2017-06-14 16:09 ` Andrea Arcangeli
2017-06-15 4:43 ` kbuild test robot
2017-06-14 13:51 ` [PATCH 2/3] mm: Do not loose dirty and access bits in pmdp_invalidate() Kirill A. Shutemov
2017-06-15 8:48 ` kbuild test robot
2017-06-14 13:51 ` [PATCH 3/3] mm, thp: Do not loose dirty bit in __split_huge_pmd_locked() Kirill A. Shutemov
2017-06-14 14:18 ` Martin Schwidefsky
2017-06-14 15:31 ` Andrea Arcangeli
2017-06-15 8:46 ` Kirill A. Shutemov
2017-06-14 15:28 ` Aneesh Kumar K.V
2017-06-14 14:06 ` [HELP-NEEDED, PATCH 0/3] Do not loose dirty bit on THP pages Martin Schwidefsky
2017-06-14 15:25 ` Aneesh Kumar K.V
2017-06-14 16:55 ` Will Deacon
2017-06-14 17:00 ` Vlastimil Babka [this message]
2017-06-15 1:36 ` Aneesh Kumar K.V
2017-06-15 1:05 ` Aneesh Kumar K.V
2017-06-15 2:50 ` Aneesh Kumar K.V
2017-06-15 8:48 ` Kirill A. Shutemov
2017-06-15 9:36 ` Aneesh Kumar K.V
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