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 bug? > 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... 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 Thanks, Cole -- xen mailing list xen@xxxxxxxxxxxxxxxxxxxxxxx https://admin.fedoraproject.org/mailman/listinfo/xen
