RE: [Xen-devel] disable qemu PCI devices in HVM domains

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

> > Is the 'pci unplug' as simple as making a call somewhere like
> > pci_unplug(id of ide adapter)? I'm concerned that Windows may not
like
> > this.
> 
> My own opinion is that the ioports are fine, but they should be
offsets
> from
> the xen-platform-pci device's ioport bar. Also we ought to document
the
> ports in xen-platform-pci's source file, as it's going to start
getting
> messy in there.
>
> I'm not sure if the approach taken by the Citrix drivers could be at
all
> useful. Cc'ing Steven Smith in case he has any comments to make.

Citrix use fixed ports for logging. The problem with using
xen-platform-pci's ioport range is that I can only get to them once the
windows pci bus driver has enumerated all the devices, and it's too late
by then as Windows has already enumerated PDO's for all the devices. The
only way around this would be to send an 'unplug' event to xen to remove
the PCI devices, but is the standard PCI bus emulated by qemu hotplug
capable? And would windows even cope with a hotplug event that early in
the boot process?

A completely different way of solving this (as per another previous
email) is for qemu to (optionally) emulate things at the int13 level
rather than at the pci device level. That way there would be no PCI
device at all and Windows would only ever see my drivers. We can already
do this for net, but obviously that isn't required for booting
(normally). So /dev/hd[a-d] would be PCI devices and anything else would
be hooked into int13.

If only Windows were more like Linux...

James


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