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

[Yuji Shimada <shimada-yxb@xxxxxxxxxxxxxxx>]

Thank you for your comments.

On Wed, 18 Feb 2009 11:29:54 +1100
"James Harper" <james.harper@xxxxxxxxxxxxxxxx> wrote:

> > 
> > 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.

When "ioemu:" or "type=ioemu" are not specified, both emulated device
and PV device are enabled. This is current xen's behavior.

So my idea does not break your usage.

> 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.

I think xen's users are not interested in whether platform device is
enabled or disabled. When they find that the device manager shows "!",
they will complain. On the other hand, they are interested in type of
disk and vif, because this affects the performance of disk and vif. So
I think it is better to use "ioemu:" and "type=ioemu".

What do you think about this?

Thanks,
--
Yuji Shimada


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