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Re: [Xen-users] FreeBSD + Xen 3.2.1 + HVM assorted problems

To: Freddie Cash <fjwcash@xxxxxxxxx>
Subject: Re: [Xen-users] FreeBSD + Xen 3.2.1 + HVM assorted problems
From: Joe Auty <joe@xxxxxxxxxxxxxxx>
Date: Wed, 02 Jul 2008 16:50:50 -0400
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Freddie Cash wrote:
On Tue, Jul 1, 2008 at 11:31 PM, Joe Auty <joe@xxxxxxxxxxxxxxx> wrote:
Hash: SHA1

Well, I solved one of my problems (problem #2) - The 64 bit version of
FreeBSD does not work as a guest OS :)

Yes it does.  64-bit 6.3 and 7.0 both run in Xen 3.2 HVMs -- if you
use AMD CPUs.  There's a bunch of niggles in the Intel CPU
virtualisation implementation that cause FreeBSD guests to crash/not
work.  Supposedly, these are fixed in Xen 3.2.1.  However, we don't
use Intel CPUs, so we've never been bitten by these issues.

If you search the -stable and -current mailing lists, I posted the
config files I used to get FreeBSD 6.3 and 7.0 running in Xen 3.2 HVMs
on Debian (using the kernel from Ubuntu).

However, if you want things to be simple, stop using Xen and stick to
KVM, especially with KVM-70 and Linux Kernel 2.6.24.

I beg to differ, as I've been wrestling with this non-stop over the last several days.

You're absolutely right that Intel is a sticking point, and I'm on Intel hardware which has compounded the problem. You're right that this is fixed in 3.2.1 with Xen custom built with the "vmxassist=n" option. My install was derived myself from an RPM I modified to add this option, I have yet to try compiling this by hand since I've been getting compile errors... So, you might end up being right here, but so far this has not been the case for me.

With my custom Xen install, I can get past the BTX halted errors that occurred before I recompiled Xen via my source RPM, but the FBSD kernel doesn't want to properly recognize disks that have been presented to the domain.

I can take my domain config and point it at the 7.0 disk one 386 CD and have it boot just beautifully, and then point the exact same config at the amd64 disk one CD and have it stuck at "unable to mount root". This is all under CentOS 5.2.

You're right that KVM might ultimately be a better option for me... I've gotten FreeBSD to work in KVM weeks ago - it was a piece of cake. What I'd like to do is benchmark i386 FreeBSD in Xen vs. amd64 FreeBSD in KVM to see which is faster. If you'd like I can share my results.

I'd also be happy to inform you guys of when/if I get FreeBSD amd64 7 working, as well as provide instructions...

Joe Auty
NetMusician: web publishing software for musicians

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