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

[Anthony Liguori <aliguori@us.ibm.com>]

On 06/07/2012 12:39 PM, li zhang wrote:
> On Thu, Jun 7, 2012 at 9:15 AM, Anthony Liguori<aliguori@us.ibm.com>  wrote:
>
> Hi Anthony,
>
> I think we can add usb to machine option, and set usb on as default in
> qemu, right?
> Does it conflict with "-device pci-ohci" ?

libvirt would want to pass '-machine type=pseries,usb=off' instead of passing 
'-M pseries'.

It could then use '-device pci-ohci'

Regards,

Anthony Liguori

>
> Libvirt will parse a xmlfile to qemu commands with -nodefault
> configuration.
>
> For example:
> /home/zhlbj/development/qemu-impreza/ppc64-softmmu/qemu-system-ppc64 -M
> pseries -enable-kvm -m 1024 -mem-prealloc -mem-path
> /dev/hugepages/libvirt/qemu -smp 2,sockets=2,cores=1,threads=1 -name $1
> -nodefconfig -nodefaults -chardev
> socket,id=charmonitor,path=/usr/local/var/lib/libvirt/qemu/$1.monitor,server,nowait
> -mon chardev=charmonitor,id=monitor,mode=readline -rtc base=utc -device
> spapr-vscsi,id=scsi0 -drive
> file=/home/zhlbj/kvm-test/fedora.img,if=none,id=drive-scsi0-0-0,format=raw
> -device
> scsi-disk,bus=scsi0.0,scsi-id=0,drive=drive-scsi0-0-0,id=scsi0-0-0,bootindex=1
> -chardev pty,id=charserial0 -device spapr-vty,chardev=charserial0 -device
> pci-ohci,id=usb,bus=pci,addr=0x1.0x2 -vnc 127.0.0.1:12 -vga std -device
> virtio-balloon-pci,id=balloon0,bus=pci,addr=0x3
>
> I think we still need to use "-device " option to add usb controller for
> configuring specific usb model.
>
>
>
>> libvirt can still happily name the usb controller whatever it wants.  But
>> the end result is a less magical command line.
>>
>> 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.
>>>
>>
> Yes, this problem is that: when the usb_enable is set as 1, it will create
> one pci-ohci controller.
> When the command is using "-device pci-ohci", it will create another
> pci-ohci controller.
> And one error occurs. I traced the code, it shows that there two places to
> call
> pci_create_multifunction(bus, devfn, bool,  "pci-ohci").
>
> One place is in the spapr.c, it means that when vga is enabled, usb_enable
> is set 1.
> it will create one pci-ohci controller.
> Another place is in the vl.c,
> if (qemu_opts_foreach(qemu_find_opts("device"), device_help_func, NULL, 0)
> != 0)
> It will create another pci-ohci controller according to "-device pci-ohci"
> option.
> It seems that usb_enable variable setting and "-device pci-ohci" option
> conflict.
> It can't detect the existing pci-ohci controller.
>
>
>>>   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
>>>>>>
>>>>>>
>>>>>>
>>>>>
>>>>>
>>>
>>>
>>
>
>