RE: [Xen-users] GPLPV / Passing devices to HVM

["James Harper" <james.harper@xxxxxxxxxxxxxxxx>]

> just wondered after I read about devices passed through in HVM if the
> following if still true: (for Xen3.2.1)
> 
> - a Domain running in HVM cannot get forwarded any other device than a
> USB device.
> - the USB device forwarding is not too stable
> - PCI forwarding is not possible without processor support and Xen
> support.
> - The GPLPV tools won't change anything with that.

The GPLPV drivers need to hide/disable the qemu network and disk
devices. If the network devices are not disabled I found that dom0's
network would break for a few seconds. If the disk devices are not
disabled then your DomU filesystem gets corrupted. Corrupted badly
enough that the only option is a restore or rebuild.

Previous versions of the GPLPV drivers 'hid' the qemu devices by
preventing their enumeration, but for reasons unknown this didn't work
on some platforms. The current version installs itself as a 'filter'
driver for all disk (ide and scsi) and network devices. When GPLPV is
not specified, the filter fails the 'start' irp for devices on the 'xen
bus'. When GPLPV is specified the filter fails the 'start' irp for
devices on the pci bus.

If your PCI passthrough device reports itself as an ide, scsi, or
network device, then the xenhide filter will not allow it to start. I
have at least one report of a dvb card reporting itself as a network
device (maybe they all do this?) so it will be blocked when gplpv is
specified.

I'm considering my options on ways to get around this at the moment...

James

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