libvirt: how to prevent "accel=kvm" - qemu

Question

First, some background:
I suppose I've found a bug with KVM, at least on my system.
When I try to install Windows XP via virt-manager, the installer aborts/reboots.
But if I run a raw qemu-system-i386 command (see below), it succeeds.
From looking at the logs in /var/log/libvirt/qemu/..., the key difference is the "accel=kvm" argument (equivalent to -enable-kvm).
So, narrowing it down, this command succeeds:
qemu-system-i386 \
-m 512 \
-usb \
-cdrom path/to/WinXP_CD.iso \
-boot d \
"$image"
But this next command results in an infinite series of reboots. The XP installer starts, but after scanning the system, just reboots rather than proceeding:
qemu-system-i386 \
-enable-kvm \
-m 512 \
-usb \
-cdrom path/to/WinXP_CD.iso \
-boot d \
"$image"
Perhaps you don't believe I have KVM working properly on my system.
But, I can install other OSes (eg: FreeBSD) using KVM just fine. This seems to be XP-specific.
So now, my questions:
How do I force libvirt to NOT use KVM for a chosen VM? Ideally via virt-manager, but I'm fine with virsh too.
I imagine somewhere in the mess of XML is some setting, but I'm not terribly familiar.
aside: any idea where I should log this bug? Against KVM? Libvirt? QEMU?

Answer 1

Well, I managed to hack around this, but I'm sure there's a more pretty way.
Basically, that -enable-kvm option corresponds to the type="kvm" value in your domain XML file. See libvirt documentation.
But there seems to be no way to change this from virt-manager. I'm not familiar enough with virsh yet to do it that way either. So, I just manually edited my XML file like so:
$ sudoedit /etc/libvirt/qemu/myxp.xml
I did this while virt-manager was closed.
When I opened it, the setting did not seem to stick. For some reason, I seemed to need to run:
$ sudo virsh define /etc/libvirt/qemu/myxp.xml
to get it to stick.
Anyway, after that little dance, then in virt-manager, in the `Overview' tab for my VM, it says "Hypervisor: QEMU TCG", where it had "KVM" before.
And now, the XP installer works!
Again, probably a better way, but good enough for now.
Presumably, performance will be poorer with KVM disabled. I still don't know who to send a bug, or whether this is a QEMU or KVM issue, at its core.

Answer 2

You can change
<domain type="kvm">
to
<domain type="qemu">
as as stated in the documentation.
To edit xml of VM in virt-manager you should activate xml editing in parameters and press "xml" tab.