On Wed, Sep 16, 2015 at 03:48:34PM -0400, Cole Robinson wrote:
> On 09/15/2015 05:35 PM, M A Young wrote:
> > On Tue, 15 Sep 2015, Cole Robinson wrote:
> >> Anyone know how to get fedora + xen running in a KVM VM? I'd like to be
> >> able
> >> to do basic xen/libxl/libvirt testing without needed to reboot a physical
> >> machine.
> >> Trying with F23 AMD host, F22+xen L1, trying to boot into xen in the L1 VM
> >> just reboots very soon after trying to boot the kernel. Tried disabling all
> >> virtio for L1 VM, disabling virt extensions for the L1 VM, but it didn't
> >> seem
> >> to change anything. Unfortunately the messages scroll by so quickly I can't
> >> tell what's happening right before it reboots, and all efforts to convince
> >> it
> >> to print more debugging haven't worked.
> >> FWIW this does work with rhel5+xen L1, but that's a world away at this
> >> point.
> >> So anyone know if it's even possible? Is there a trick to it? If not,
> >> suggestions on getting more debug output from xen + grub2?
> > It works for me after a basic and probably sub-optimal install, as follows
> > * qemu-kvm -cdrom Fedora-Server-DVD-x86_64-22.iso -m 1024 -hda kvm.img
> > * do a minimal install
> > * after reboot dnf install xen xen-hypervisor
> > * select "Fedora, with Xen hypervisor" in the boot menu
> Thanks, the minimal command line worked for me. It allowed me to track it back
> and and find the culprit.
> It comes down the -cpu value; the default qemu64 works, but any Opteron_* or
> -cpu host do not work. I had played around with this originally thinking maybe
> it was a nested virt issue, and tried Opteron_G1 which lacks svm, but never
> actually tried the default qemu64 cpu...
> So this doesn't work:
> $ qemu-kvm -m 1024 -hda kvm.img -cpu Opteron_G1
> However this does:
> $ qemu-kvm -m 1024 -hda kvm.img -cpu Opteron_G1,family=6
> qemu64 uses family=6, but Opteron_G1 uses family=15. I see there's some bits
> of qemu that trigger off family>6 regarding setting some bits about MCE, but I
> tried disabling those in the code and things still errored. More data points:
> - TCG works fine for every combo I tried
> - cpu qemu64,family=15 fails
> - None of this affects my intel host, all these work fine: -cpu host, -cpu
> Opteron_G1, -cpu qemu64, -cpu qemu64,family=15
> So given all that, anyone have a suggestion of whether this is a KVM or Xen
> > If you need more debugging, boot without xen, and edit the grub.cfg file,
> > adding console=com1 after xen.gz and replacing rhgb quiet with
> > console=hvc0 in the 'Fedora, with Xen hypervisor' section, then boot kvm
> > with -serial eg. -serial file:boot.log which should give you xen logging
> > after grub has finished.
> Unfortunately I couldn't get anything else extra out of xen using any of these
> options or the ones Major recommended... in fact I couldn't get anything to
> the serial console at all. console=con1 would seem to redirect messages since
> they wouldn't show up on the graphical display, but nothing went to the serial
> log. Maybe I'm missing something...
Perhaps you need to enable some KVM setting to use the COM1 and output
the value somewhere?
> sync_console gives an extra message but that's all I could see. Is
> console=hvc0 correct for a KVM guest, or is that only going to work for
> xen-on-xen ? I tried console=ttyS0 as well but it didn't make a difference
But since you are using QEMU you can figure out where the CPU is at.
As in you should be able to get an EIP pointer and perhaps even a
stack? There are some magic commands in the QMEU monitor pty.
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