linux-kernel - Re: [PATCH RFC 0/3] pagemap: make useable for non-privilege users

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Date:	Thu, 14 May 2015 19:40:30 +0100
From:	Mark Williamson <mwilliamson@...o-software.com>
To:	Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
Cc:	linux-mm@...ck.org, Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	kernel list <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Pavel Emelyanov <xemul@...allels.com>,
	Linux API <linux-api@...r.kernel.org>,
	Andy Lutomirski <luto@...capital.net>,
	Vlastimil Babka <vbabka@...e.cz>, Pavel Machek <pavel@....cz>,
	Mark Seaborn <mseaborn@...omium.org>,
	"Kirill A. Shutemov" <kirill@...temov.name>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Daniel James <djames@...o-software.com>,
	Finn Grimwood <fgrimwood@...o-software.com>
Subject: Re: [PATCH RFC 0/3] pagemap: make useable for non-privilege users

Hi Konstantin,

I modified our code to check for the map-exclusive flag where it used
to compare pageframe numbers.  First tests look pretty promising, so
this patch looks like a viable approach for us.

Is there anything further we can do to help?

Thanks,
Mark

On Tue, May 12, 2015 at 12:13 PM, Mark Williamson
<mwilliamson@...o-software.com> wrote:
> Hi Konstantin,
>
> Thanks very much for continuing to look at this!  It's very much
> appreciated.  I've been investigating from our end but got caught up
> in some gnarly details of our pagemap-consuming code.
>
> I like the approach and it seems like the information you're exposing
> will be useful for our application.  I'll test the patch and see if it
> works for us as-is.
>
> Will follow up with any comments on the individual patches.
>
> Thanks,
> Mark
>
> On Tue, May 12, 2015 at 10:43 AM, Konstantin Khlebnikov
> <khlebnikov@...dex-team.ru> wrote:
>> This patchset tries to make pagemap useable again in the safe way.
>> First patch adds bit 'map-exlusive' which is set if page is mapped only here.
>> Second patch restores access for non-privileged users but hides pfn if task
>> has no capability CAP_SYS_ADMIN. Third patch removes page-shift bits and
>> completes migration to the new pagemap format (flags soft-dirty and
>> mmap-exlusive are available only in the new format).
>>
>> ---
>>
>> Konstantin Khlebnikov (3):
>>       pagemap: add mmap-exclusive bit for marking pages mapped only here
>>       pagemap: hide physical addresses from non-privileged users
>>       pagemap: switch to the new format and do some cleanup
>>
>>
>>  Documentation/vm/pagemap.txt |    3 -
>>  fs/proc/task_mmu.c           |  178 +++++++++++++++++-------------------------
>>  tools/vm/page-types.c        |   35 ++++----
>>  3 files changed, 91 insertions(+), 125 deletions(-)
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