Re: [Qemu-devel] [qemu-devel][RFC] Enable usb with default options

[Benjamin Herrenschmidt <benh@au1.ibm.com>]

On Thu, 2012-06-07 at 09:15 +0800, Anthony Liguori wrote:

> You misunderstand what I'm saying.
> 
> -nodefault is a dumb option.  It's semantics are poorly defined because it 
> depends on machine.  Further complicating those semantics by adding more magic 
> for -M spapr just makes the situation worse.
> 
> I'm suggesting to make use of the -machine option to allow usb to be disabled.  So:
> 
> qemu-system-ppc64 -machine type=spapr,usb=off
> 
> libvirt can still happily name the usb controller whatever it wants.  But the 
> end result is a less magical command line.

Allright, what I was missing is -machine option with arguments, I only
knew about -M <name> :-)
 
That definitely sounds like the right way to go. However, I do wonder to
what extent we should still also support -nodefault because that's what
libvirt does today or we just don't give a shit ?

Li, can you do something along the lines of what Anthony described ? By
default, you should have -vga std and usb OHCI with mouse and keyboard.

Feel free to replace the patches I currently have in our internal tree
for enabling -vga etc... and post the result publicly, however, please
note in the comments that for that stuff to work, there's a dependency
on the iommu patch series.

Cheers,
Ben.

> Regards,
> 
> Anthony Liguori
> 
> >
> > The problem is that for things created "by default", libvirt then makes
> > horrible assumptions about the default 'names' and bus names as well,
> > which is why it's generally somewhat saner to let it create the machine
> > from scratch (well, sorry for putting "sane" and "libvirt" in the same
> > sentence but you get my idea I think :-)
> >
> >>> -vga should only affect vga (a shortcut for -device
> >>> pick_your_vga_poison)
> >>
> >> Ack.
> >
> > (Note: This is in reference to our current internal patch which
> > automagically adds OHCI and USB kbd + mouse when you do -vga, that's not
> > something that should survive upstream).
> >
> >>> -usb should be essentially useless by default unless -nodefault is
> >>> passed in which case it is necessary to enable usb support, and -device
> >>> (or equivalent) to manually add the keyboard and mouse (libvirt).
> >>
> >> If you want pseries to always have usb, just make it there by default and yeah,
> >> -usb would be useless.  If you want the option to not have usb, introduce a
> >> machine option I guess.
> >
> > Ah, I'm not familiar with "machine options" ... or do you mean another
> > machine type ? ie -M pseries_nousb ? :-)
> >
> > The problem with things like USB by default is that libvirt will fuckup
> > (at least that's my understanding from what Li says) bcs it's going to
> > try to create a separate USB bus and can't seem to figure out how to
> > reference the existing one, etc...  In fact it even tries to re-use the
> > PCI bus/dev where the original OHCI is created an that clashes.
> >
> >> I think it's over thinking it though.  There's little harm in having a usb
> >> controller present all the time.
> >
> > That makes more sense I agree, I'm just annoyed by the whole libvirt
> > business which seems to have some pretty hard assumptions that with
> > -nodefault you don't get anything by default, and I think it makes some
> > sense to keep that option around.
> >
> > Cheers,
> > Ben.
> >
> >> Regards,
> >>
> >> Anthony Liguori
> >>
> >>>
> >>> That's the best I can think of ... however it might be a bit tricky
> >>> seeing how qemu does things in vl.c at the moment, we might want to
> >>> introduce a default_usb variable which is used to set usb_enabled.
> >>>
> >>> BTW. The mac models should essentially behave the same, at least the
> >>> 64-bit one (32-bit supports CUDA for keyboard/mouse so USB isn't
> >>> strictly necessary).
> >>>
> >>> Cheers,
> >>> Ben.
> >>>>
> >>>> Thanks.
> >>>>
> >>>> On Tue, Jun 5, 2012 at 5:48 PM, li zhang<zhlcindy@gmail.com>   wrote:
> >>>>           Hi all,
> >>>>
> >>>>           For pseries, when creating VMs with "-vga std",
> >>>>           it requires usb mouse and usb kbd devices to be added.
> >>>>
> >>>>           But with default options, vga is enabled and usb is disabled.
> >>>>           User may use default options as the following commands:
> >>>>
> >>>>           $qemu -M pseries
> >>>>
> >>>>           If vga is enabled, usb mouse and usb kbd is disabled,
> >>>>           the mouse and kbd can't be used. So it's very hard for
> >>>>           users to use.
> >>>>
> >>>>           I think it's necessary to enable usb with default options.
> >>>>
> >>>>           Any idea about that?
> >>>>           Your comments  are very appreciated. :)
> >>>>
> >>>>           Thanks.
> >>>>            -Li
> >>>>
> >>>>
> >>>>
> >>>>
> >>>> --
> >>>>
> >>>>
> >>>> Best Regards
> >>>> -Li
> >>>>
> >>>>
> >>>
> >>>
> >
> >