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Re: [Xen-devel] trap/interrupt gate for hypercall

To: "Tian, Kevin" <kevin.tian@xxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] trap/interrupt gate for hypercall
From: Keir Fraser <keir@xxxxxxxxxxxxx>
Date: Tue, 15 May 2007 16:02:07 +0100
Cc: "Liu, Jinsong" <jinsong.liu@xxxxxxxxx>
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On 15/5/07 15:43, "Tian, Kevin" <kevin.tian@xxxxxxxxx> wrote:

> Just a curious question about IDT descriptor type for hypercall. What's
> the reason to use interrupt-gate type (14) for hypercall (0x82) on 32bit
> Xen?

Everything's an interrupt gate on 32-bit Xen, so that we can safely
(atomically) save away guest segment register state. NMI is the only real
pain, and I suppose MCE too. Coincidentally Jan just emailed about this very

 -- Keir

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