linux-kernel - Re: DRAM unreliable under specific access patern

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Message-ID: <CALCETrV1O1MFJeY6WacF+QHdBGG7HoHdVQy=n951=Y+=g+h7mQ@mail.gmail.com>
Date:	Mon, 5 Jan 2015 17:57:24 -0800
From:	Andy Lutomirski <luto@...capital.net>
To:	"Kirill A. Shutemov" <kirill@...temov.name>
Cc:	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
	Pavel Machek <pavel@....cz>,
	Mark Seaborn <mseaborn@...omium.org>,
	kernel list <linux-kernel@...r.kernel.org>
Subject: Re: DRAM unreliable under specific access patern

On Mon, Jan 5, 2015 at 5:47 PM, Kirill A. Shutemov <kirill@...temov.name> wrote:
> On Mon, Jan 05, 2015 at 11:50:04AM -0800, Andy Lutomirski wrote:
>> On Mon, Jan 5, 2015 at 11:23 AM, One Thousand Gnomes
>> <gnomes@...rguk.ukuu.org.uk> wrote:
>> >> In the meantime, I created test that actually uses physical memory,
>> >> 8MB apart, as described in some footnote. It is attached. It should
>> >> work, but it needs boot with specific config options and specific
>> >> kernel parameters.
>> >
>> > Why not just use hugepages. You know the alignment guarantees for 1GB
>> > pages and that means you don't even need to be root
>> >
>> > In fact - should we be disabling 1GB huge page support by default at this
>> > point, at least on non ECC boxes ?
>>
>> Can you actually damage anyone else's data using a 1 GB hugepage?
>
> hugetlbfs is a filesystem: the answer is yes. Although I don't see the
> issue as a big attach vector.

What I mean is: if I map a 1 GB hugepage and rowhammer it, is it
likely that the corruption will be confined to the same 1 GB?

--Andy

>
> --
>  Kirill A. Shutemov



-- 
Andy Lutomirski
AMA Capital Management, LLC
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