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Re: [Xen-users] Re: [Xen-devel] Re: need to compile 32bit on x86_64 cpu

To: "Petersson, Mats" <Mats.Petersson@xxxxxxx>
Subject: Re: [Xen-users] Re: [Xen-devel] Re: need to compile 32bit on x86_64 cpu
From: "Anand Gupta" <xen.mails@xxxxxxxxx>
Date: Fri, 23 Jun 2006 03:13:53 +0530
Cc: Harry Butterworth <harry@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx>, Jerone Young <jyoung5@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx, Xen Users <Xen-users@xxxxxxxxxxxxxxxxxxx>, Andi Kleen <ak@xxxxxxx>
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Thanks for all the explanation Mats.

Well i didn't think of running 64bit on top of 32bit xen, however i certainly thought about vice-versa. However your explanation has made it clear it isn't possible.

Thanks for all the help.

On 6/23/06, Petersson, Mats <Mats.Petersson@xxxxxxx> wrote:
No, you can only run the same-bitness for Xenified guests. Xen 3.x supports unmodified guests at any level of bitness (up to whatever Xen itself is, you obviously can't run a 64-bit unmodified guest on top of a 32-bit Xen).
 
But for Xenified guests, the Xen-build and the Guest-OS must be the same - this is because it's actually quite complicated to translate  the different page-table levels and map the memory such that the guest can access it, etc [not exactly rocket science, of course, but it does make life more difficult for the hypervisor].
 
It has been discussed to make a shim-layer that translates the Xen-calling interface.
 
Is there any particular reason you feel that you must run a 32-bit guest-OS. Almost all applications will work just fine in a 64-bit guest. Of course, there are some exceptions... If so, then you do need to move to 32-bit host-OS as well as guest-OS, yes.


--
regards,

Anand Gupta
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