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

[Anthony Liguori <anthony@codemonkey.ws>]

On 06/07/2012 11:00 AM, Benjamin Herrenschmidt wrote:
> 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 ?

Well -nodefault will already suppress a bunch of things but you don't have to 
worry about -nodefault being the mechanism to suppress everything.

Regards,

Anthony Liguori

> 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
>>>>>>
>>>>>>
>>>>>
>>>>>
>>>
>>>
>
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