On Fri, Aug 02, 2013 at 10:31:11AM +0200, Paolo Bonzini wrote: > On 08/02/2013 12:42 AM, Eric Blake wrote: > >On 08/01/2013 04:23 PM, Paolo Bonzini wrote: > >>>Automatic devices with no command line argument have proven to be a > >>>nightmare for libvirt as well. Although the just-released libvirt 1.1.1 > >>>now supports the <on_crash> element for controlling the command line > >>>parameters of qemu related to how qemu will behave when the pvpanic > >>>device is triggered, I would also welcome having the ability to control > >>>whether the guest even has a pvpanic device exposed, just as we can > >>>control whether a guest has a memballoon device exposed. > >> > >>This is quite different from memballoon. > >> > >>pvpanic is a single I/O port, it doesn't use up a PCI slot (thus > >>causing conflicts with other devices at the same address). > >> > >>Perhaps this issue is simply fixed by making the _STA method > >>return 0x0B instead of 0x0F (i.e. turning off the "show in user > >>interface" bit). > > > >That may "fix" the issue of a windows guest showing the yellow ! mark, > >but what if, down the road, someone writes an actual windows driver that > >is aware of that port and how to make a windows BSOD write a panic > >notification to the port? How does a user go about installing such a > >driver if the device is not exposed in the user interface list of devices? > > The user can still manually install a driver even for a device that > is not exposed. > > Having to manually specify the pvpanic device would be yet another > knob that nobody uses. Panic notification is a useful feature that > should be supported with no particular intervention from the user. Yep, that was the big motivation behind doing it as an I/O port that we could have enabled by default, as opposed to a virtio serial device or some other paravirt device that required explicit configuration. Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :| -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list