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

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.


Anand Gupta
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