From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Jan Beulich" <jbeulich@novell.com>
Subject: Re: System Calls in x86_32
Date: Thu, 19 Jun 2008 15:42:55 +0100
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To: Grzegorz Milos <gm281@cam.ac.uk>, Ahmed Moneeb Azab <amazab@ncsu.edu>
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>The reason why Xen wants to intercept the
>interrupts is that we could be executing 32bit guest, or an HVM guest
>etc (look through the definition of int80_direct_trap for details).

Not exactly. First of all, HVM guests are don't-care here - they handle
int 0x80 with their own IDT. 64-bit guests must go through Xen because
guest and kernel run in ring 3, and the kernel mode flag must be set
correctly, which can only be donein Xen. 32-bit guest must go through
Xen because x84-64 doesn't know 32-bit gates (i.e. the target code
selector of any gate must be a 64-bit code segment).

Jan