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Re: [Xen-devel] Debian kernel doesn't support DomU bit width != Dom0 bit

To: James Harper <james.harper@xxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] Debian kernel doesn't support DomU bit width != Dom0 bit width for PV drivers?
From: "Daniel P. Berrange" <berrange@xxxxxxxxxx>
Date: Fri, 1 Feb 2008 22:30:45 +0000
Cc: xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>
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On Sat, Feb 02, 2008 at 09:25:27AM +1100, James Harper wrote:
> In trying to figure out why my Xen Windows PV drivers don't work
> properly when the frontend and backend are different bit width modes (eg
> 32, 64), I figured out that the same is true for Linux domains. I tested
> a 32 bit DomU with a 64 bit Dom0, and get a crash almost as soon as the
> blkfront driver is started, and a "(XEN) grant_table.c:264:d0 Bad flags
> (0) or dom (0). (expected dom 0)" message logged in 'xm dmesg'.
> My suspicion then is that the Debian kernel's blkback driver doesn't pay
> attention to the 'protocol' set by the frontend, even though blkfront
> driver included in the Debian kernel does actually set it.

Depends what Xen version their kernel / userspace is based on. IIRC you
need to have at least Xen 3.1.1  to get 32-on-64 working properly - the
compatability 'protocol' stuff didn't make the original 3.1.0 release

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