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[Xen-devel] idtr

To: xen-devel@xxxxxxxxxxxxxxxxxxx
Subject: [Xen-devel] idtr
From: "Travis Johnson" <travis.jo@xxxxxxxxx>
Date: Tue, 19 Dec 2006 09:37:10 -0500
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Question:
When a guest domain does a "lidt" (the x86 instruction) to update the pointer to the IDT where does this information get stored inside Xen (assuming it does). I know Xen can interject interrupts into a domain and that the "guest_vcpu_context" struct contains an array that represents the virtual IDT but how does the virtual IDT relate to the actual IDT the guest OS uses and is pointed to by it's idtr. It seems logical to me that the idtr must be stored inside the vcpu at some point somewhere since I can run a "sidt" and get what seems like a reasonable address (from the guest's point of view). I've also used "lidt"'s without crashing the system so Xen handles the update correctly.

I'm using HVM(VMX) guests on 64bit Xen (3.0.3 - the stable tarball from xensource). The guests run FC6.

Thanks. This list is always a good read.
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