From: Jeremy Fitzhardinge <jeremy@goop.org>
To: Min Lee <min.lee@gatech.edu>
Cc: Xen-devel@lists.xensource.com
Subject: Re: [Q] guest and user protection on x86-64 by paging
Date: Sun, 01 Aug 2010 23:31:59 -0700 [thread overview]
Message-ID: <4C56665F.6030808@goop.org> (raw)
In-Reply-To: <4C559A4A.1030809@gatech.edu>
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.
J
next prev parent reply other threads:[~2010-08-02 6:31 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-08-01 16:01 [Q] guest and user protection on x86-64 by paging Min Lee
2010-08-02 6:31 ` Jeremy Fitzhardinge [this message]
2010-08-02 14:35 ` Min Lee
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