Re: [PATCH V7 6/7] xl: add usb-assignable-list command

[Juergen Gross <jgross@suse.com>]

On 10/07/2015 01:20 PM, George Dunlap wrote:
> On 07/10/15 12:09, Ian Campbell wrote:
>> On Wed, 2015-10-07 at 11:10 +0100, George Dunlap wrote:
>>
>>>> So IMHO xl usb-assignable-list should behave like pci-assignable-list by
>>>> default.
>>>
>>> I don't think that's really suitable.
>>
>> Then I'm terribly confused because I thought that is what you were
>> initially advocating.
>
> I think in v3 I was trying to come up with a different name
> (usb-available-list or something); but my main point was that it
> *shouldn't* be named similarly but have different functionality.
>
> As I said, for this am I was ready to just let it slide; I just wanted
> to make sure other people knew what was being let slide. :-)
>
>>
>> [...]
>>
>>> For USB, there is no "assignable" stage -- "usb-attach" will take it
>>> all the way from being assigned to a driver to being assigned to the
>>> guest.  (You can think of this as pci-attach with "seize=1" always.)
>>> So making "usb-assignable-list" act like "pci-assignable-list" doesn't
>>> actually make any sense.
>>
>> Thanks. Jeurgen has also explained this.
>>
>> Do you agree that adding a dummy usbback driver just for the purposes of
>> adding this extra "assignable" state doesn't make sense?
>
> Yes, I agree.
>
>>>> Now, maybe it should also support some sort of --all or --full or --host
>>>> option which lists everything, ideally with some indication as to whether
>>>> they are attached to usbback or not and using syntax which can just be cut
>>>> -and-pasted into a cfg file (without at least one of those it's just a
>>>> pointless reimplementation of lsusb).
>>>>
>>>> However I think --all/full/host is an optional extra.
>>>
>>> Juergen suggested having "usb-list" have an --all option in the v3
>>> discussion.  If like me you're concerned about confusing people, then
>>> having --all and --host is probably the best option.
>>>
>>> Thoughts?
>>
>> If there is no assignable state in usb then I guess I don't really
>> understand what usb-list-assignable would even be for, so I don't really
>> understand why anyone is arguing what semantics it should have (my initial
>> reply was predicated on this state existing and it therefore being useful
>> to discuss how the command should behave).
>>
>> Given that doing something with usb-list seems most plausible _if_ we need
>> some sort of thing like that at all.
>>
>> What would "usb-list --all" add over and above using lsusb?
>>
>> I take it that as things stand in patch #5:
>>      # xl usb-list <vm>
>> will list the usb devices attached to <vm> and that:
>>      # xl usb-list
>> will list the usb devices attached to every vm, is that
>> correct?
>>
>> So the idea would then be to add some way of listing the devices not included in "xl usb-list", which are notionally attached to dom0, but via physical USB and not PV usb.
>
> The "usb-assignable-list" that Chunyan has submitted will give you a
> list of all dom0 USB devices that have not yet been assigned to a guest.
>   It should be basically equivalent to "lsusb", except that it filters
> out devices which have already been assigned to VMs.
>
> In the e-mail you respond to, I was suggesting that
>
> # xl usb-list --all
>
> would show you usb devices attached to every VM, and also USB devices
> attached to no VM, and that
>
> # xl usb-list --host
>
> would show you only host usb devices not attached to any VM.
>
> I think it's the second bit if functionality which Juergen is keen be
> available in some form or other.

Exactly.

BTW: I've explained that in another reply, but my mail client has chosen
to send it via another account - I've no idea how that happened. So now
my wife has some xen-devel history as well. ;-)


Juergen