RE: [Xen-devel] [RFC] Disable xen platform device when it is not needed.

[Kouya Shimura <kouya@xxxxxxxxxxxxxx>]

James Harper writes:
> > 
> > I plan to create the patch to disable xen platform device when it
> > is not needed. Please let me know if anyone has a comment.
> > 
> > Windows guest shows xen platform device as unknown
> > device with "!" mark in the device manager, when PV drivers are not
> > loaded. So I'd like to disable xen platform device.
> > 
> > If following conditions are all true, I will disable xen platform
> > device. Otherwise, xen platform device will be enabled.
> > 
> >     - All entries in "disk" parameter have "ioemu:" prefix in DEV
> field.
> >         Example:
> >         disk = [ '/var/images/guest.img,ioemu:hda,w',
> ',ioemu:hdc:cdrom,r'
> > ]
> > 
> >     - All entries in "vif" parameter have "type=ioemu".
> >         Example:
> >         vif = [ 'type=ioemu, bridge=eth0', 'type=ioemu, bridge=eth1' ]
> > 
> >     - "vscsi" parameter is not specified.
> 
> I still leave my disks and network as ioemu even when using PV drivers,
> as I simply need to use the /NOGPLPV boot option to switch back to them.
> 
> I recommend you add a 'no_platform_pci=1' option or something like that,
> rather than try and guess that the user doesn't want it.

Besides, we can add a PV disk by 'xm block-attach' command after boot.
My vote would be a 'xen_platform_pci=0' option (default=1).

> I'm also not sure that xen will boot without the disks being in ioemu
> mode, so using a non-ioemu disk for the situation where you want to use
> PV drivers will not give you a bootable system.

The PCI passthrough enables it.

Thanks,
Kouya

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