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Re: [Xen-devel] some questions about the HVM
| To: | Tim Deegan <Tim.Deegan@xxxxxxxxxx> |
|---|---|
| Subject: | Re: [Xen-devel] some questions about the HVM |
| From: | George Dunlap <dunlapg@xxxxxxxxx> |
| Date: | Tue, 30 Mar 2010 10:57:37 +0100 |
| Cc: | "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, WangWei???? <wangwei.cs@xxxxxxxxx> |
| Delivery-date: | Tue, 30 Mar 2010 02:58:42 -0700 |
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On Fri, Mar 26, 2010 at 5:58 PM, Tim Deegan <Tim.Deegan@xxxxxxxxxx> 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 _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel |
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