[Xen-devel] Re: [PATCH] mem_sharing: fix race condition of nomin

To:	Tim Deegan <Tim.Deegan@xxxxxxxxxx>
Subject:	[Xen-devel] Re: [PATCH] mem_sharing: fix race condition of nominate and unshare
From:	Jui-Hao Chiang <juihaochiang@xxxxxxxxx>
Date:	Mon, 10 Jan 2011 12:57:41 +0800
Cc:	tinnycloud <tinnycloud@xxxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
Delivery-date:	Sun, 09 Jan 2011 20:58:31 -0800
Dkim-signature:	v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:received:received:in-reply-to :references:date:message-id:subject:from:to:cc:content-type; bh=xIc1At6LOsazMbG6H3mkyChfwvbF+vhrBY4aMBkl8hw=; b=YEEXLVzRVK6XWAsZTcHq0UxkbKUYXUdp91myEAiFlbtjMzwm5aSgAc85ENT7K1ulqD gZ1fmzgvB3U81IX684OSJe9r6EKg/MJ5S1lcSN/QR2VBFby6jsKhUZJaG6XU/DRp8zaY Ilskg3Ki+kcD1JH+0M1mDj1YTWXnA1IIaKsRc=
Domainkey-signature:	a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type; b=URDHAGljqliARUUW+l49ljnJ8FCkSKkNt3PuzMaGVPBKl5Z+KHQuH0gD3v9bUr+tXz hU0qVqc9Zfq8c3+mEZz4AKMXhxGZZiK0sykw2u6zux2MHpa6hjy6qishKmXVOAXYJv65 e5U8oBrq4dejFfaiMZ2XdyKLpxkuyemjG4t7Y=
Envelope-to:	www-data@xxxxxxxxxxxxxxxxxxx
In-reply-to:	<20110107160949.GD5651@xxxxxxxxxxxxxxxxxxxxxxx>
List-help:	<mailto:xen-devel-request@lists.xensource.com?subject=help>
List-id:	Xen developer discussion <xen-devel.lists.xensource.com>
List-post:	<mailto:xen-devel@lists.xensource.com>
List-subscribe:	<http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
List-unsubscribe:	<http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
References:	<AANLkTinMp1v1zex2BfcUuszotPuxJFWZQNUp40gu_gxL@xxxxxxxxxxxxxx> <20110106165450.GO21948@xxxxxxxxxxxxxxxxxxxxxxx> <AANLkTinmpiusLqegGZA+bZWpDXPM+7Wq2nt8MZa0Ocet@xxxxxxxxxxxxxx> <AANLkTinf-A_4NEPQeCw0pftM5Bks8BYPRhMx3-stTHxa@xxxxxxxxxxxxxx> <20110107160949.GD5651@xxxxxxxxxxxxxxxxxxxxxxx>
Sender:	xen-devel-bounces@xxxxxxxxxxxxxxxxxxx

Hi, Tim:

On Sat, Jan 8, 2011 at 12:09 AM, Tim Deegan <Tim.Deegan@xxxxxxxxxx> wrote:

At 06:02 +0000 on 07 Jan (1294380120), Jui-Hao Chiang wrote:
> One of the solution is to
> (a) Simply replace shr_lock with p2m_lock.

I think this is the best choice. If we find that the p2m lock is a
bottleneck we can address it later.

Just to be skeptic.
Why doesn't mfn_to_gfn() take p2m lock when querying the p2m type? Is there any quarantee that the resulting type is correct and trustful?
For example:
(1) User1 query the p2m type:
mfn_to_gfn(...&p2mt);
if (p2mt == p2m_ram_rw) /* do something based on the p2m type result? */

(2) User2 modify the p2m type
p2m_lock(p2m);
set_p2m_entry(..... p2m_ram_rw);
p2m_unlock(p2m);

Thanks,
Jui-Hao

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel

WARNING - OLD ARCHIVES

xen-devel

[Xen-devel] Re: [PATCH] mem_sharing: fix race condition of nominate and