This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
Home Products Support Community News


Re: [Xen-devel] [Q] guest and user protection on x86-64 by paging

To: Min Lee <min.lee@xxxxxxxxxx>
Subject: Re: [Xen-devel] [Q] guest and user protection on x86-64 by paging
From: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Date: Sun, 01 Aug 2010 23:31:59 -0700
Cc: Xen-devel@xxxxxxxxxxxxxxxxxxx
Delivery-date: Sun, 01 Aug 2010 23:32:41 -0700
Envelope-to: www-data@xxxxxxxxxxxxxxxxxxx
In-reply-to: <4C559A4A.1030809@xxxxxxxxxx>
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: <4C559A4A.1030809@xxxxxxxxxx>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv: Gecko/20100720 Fedora/3.1.1-1.fc13 Lightning/1.0b2pre Thunderbird/3.1.1
 On 08/01/2010 09:01 AM, Min Lee wrote:
Hi, folks.
one question. I'll read source code, but if one can give me brief overview, it would be so helpful. On x86-64, guest and user runs both in ring 3, and protect from each other by paging mechanism. but, how? Then page table should be modified and TLB would be flushed for every system call. This would be some overhead, I think. Is this what Xen is doing?

Yes it is. 64-bit PV guests run at a considerable disadvantage. The only mitigating factor is that it sets the Global bit on usermode ptes, so that they don't get flushed from tlb during the transition.


Xen-devel mailing list

<Prev in Thread] Current Thread [Next in Thread>