From: Julien Grall <julien.grall@arm.com>
To: Paul Durrant <Paul.Durrant@citrix.com>,
"boris.ostrovsky@oracle.com" <boris.ostrovsky@oracle.com>,
David Vrabel <david.vrabel@citrix.com>,
"jgross@suse.com" <jgross@suse.com>,
"sstabellini@kernel.org" <sstabellini@kernel.org>,
"konrad.wilk@oracle.com" <konrad.wilk@oracle.com>
Cc: Andrew Cooper <Andrew.Cooper3@citrix.com>,
"steve.capper@arm.com" <steve.capper@arm.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"JBeulich@suse.com" <JBeulich@suse.com>,
"xen-devel@lists.xen.org" <xen-devel@lists.xen.org>
Subject: Re: [PATCH] xen: grant-table: Check truncation when giving access to a frame
Date: Mon, 13 Jun 2016 13:41:36 +0100 [thread overview]
Message-ID: <575EAA00.10705__12039.2905468636$1465821782$gmane$org@arm.com> (raw)
In-Reply-To: <f840483492114a56b4bada9d3367aa76@AMSPEX02CL03.citrite.net>
Hello Paul,
On 13/06/16 13:12, Paul Durrant wrote:
>> -----Original Message-----
>> From: Xen-devel [mailto:xen-devel-bounces@lists.xen.org] On Behalf Of
>> Julien Grall
>> Sent: 13 June 2016 11:51
>> To: boris.ostrovsky@oracle.com; David Vrabel; jgross@suse.com;
>> sstabellini@kernel.org; konrad.wilk@oracle.com
>> Cc: steve.capper@arm.com; Andrew Cooper; linux-kernel@vger.kernel.org;
>> xen-devel@lists.xen.org; Julien Grall; JBeulich@suse.com
>> Subject: [Xen-devel] [PATCH] xen: grant-table: Check truncation when giving
>> access to a frame
>>
>> The version 1 of the grant-table protocol only supports frame encoded on
>> 32-bit.
>>
>> When the platform is supporting 48-bit physical address, the frame will
>> be encoded on 36-bit which will lead a truncation and give access to
>> the wrong frame.
>>
>> On ARM Xen will always allow the guest to use all the physical address,
>> although today the RAM is always located under 40-bits (see
>> xen/include/public/arch-arm.h).
>>
>> Add a truncation check in gnttab_update_entry_v1 to prevent the guest to
>> give access to the wrong frame.
>>
>> Signed-off-by: Julien Grall <julien.grall@arm.com>
>>
>> ---
>> This is limiting us to a 44-bit address space whilst ARM can support
>> up to 48-bit today. This number of bit will increase to 52-bit in
>> upcoming processors [1].
>>
>> It might be good to start thinking to extend the version 1 of the
>> protocol to use 64-bit frame number.
>
> ...or simply use version 2 of the protocol.
On another mail [1], you said that "[v2] didn't scale it became
bottle-necked on dom0's grant table size,...".
So it looks like to me that version 2 is the wrong way to go.
The performance should stay the same whether the platform support
40-bit, 44-bit, 48-bit, 52-bit address space.
Regards,
--
Julien Grall
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xen.org
http://lists.xen.org/xen-devel
next prev parent reply other threads:[~2016-06-13 12:41 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1465815046-5390-1-git-send-email-julien.grall@arm.com>
2016-06-13 10:57 ` [PATCH] xen: grant-table: Check truncation when giving access to a frame David Vrabel
[not found] ` <575E9198.70103@citrix.com>
2016-06-13 11:10 ` Julien Grall
[not found] ` <575E948B.7060507@arm.com>
2016-06-13 12:20 ` Paul Durrant
2016-06-13 12:12 ` Paul Durrant
[not found] ` <f840483492114a56b4bada9d3367aa76@AMSPEX02CL03.citrite.net>
2016-06-13 12:41 ` Julien Grall [this message]
[not found] ` <575EAA00.10705@arm.com>
2016-06-13 12:42 ` Julien Grall
[not found] ` <575EAA21.4030701@arm.com>
2016-06-13 12:45 ` Paul Durrant
[not found] ` <40a70cd8036747a2801c3ebd1b299d23@AMSPEX02CL03.citrite.net>
2016-06-13 13:05 ` Julien Grall
[not found] ` <575EAFA7.4020603@arm.com>
2016-06-13 13:14 ` Paul Durrant
2016-06-13 10:50 Julien Grall
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