From: George Dunlap <dunlapg@gmail.com>
To: Tim Deegan <Tim.Deegan@citrix.com>
Cc: "xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>,
WangWei???? <wangwei.cs@gmail.com>
Subject: Re: some questions about the HVM
Date: Tue, 30 Mar 2010 10:57:37 +0100 [thread overview]
Message-ID: <de76405a1003300257g3f5d4618k7f26bc145d74115@mail.gmail.com> (raw)
In-Reply-To: <20100326165856.GA4975@whitby.uk.xensource.com>
On Fri, Mar 26, 2010 at 5:58 PM, Tim Deegan <Tim.Deegan@citrix.com> wrote:
>> I have a question about the VMEXIT in HVM.
>> Does the behavior of modifying the pte of guest OS cause a vmexit.
>
> When using shadow pagetables, yes (more precisely, modifying a page that
> is shadowed causes a VMEXIT)
...but it's complicated. We have an optimization called "out-of-sync"
such that modifying PTE may not cause a VMEXIT; instead, the VMEXIT
may happen when the virtual address the PTE controls is dereferenced
(akin to a TLB miss). As Tim said, this is only in shadow mode, if
HAP (EPT or NPT) is not present / disabled.
-George
prev parent reply other threads:[~2010-03-30 9:57 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-03-26 14:00 some questions about the HVM WangWei王伟
2010-03-26 16:58 ` Tim Deegan
2010-03-30 9:57 ` George Dunlap [this message]
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