Re: [Xen-devel] [PATCH v5 3/5] libxl: add new pvusb backend "qusb" provided by qemu

[Juergen Gross <jgross@xxxxxxxx>]

On 30/03/16 18:16, Wei Liu wrote:
> On Wed, Mar 30, 2016 at 04:34:20PM +0200, Juergen Gross wrote:
>> On 30/03/16 16:19, Wei Liu wrote:
>>> On Wed, Mar 30, 2016 at 02:05:56PM +0200, Juergen Gross wrote:
>>>> Add a new pvusb backend type "qusb" which is provided by qemu. It can
>>>> be selected either by specifying the type directly in the configuration
>>>> or it is selected automatically by libxl in case there is no "usbback"
>>>> driver loaded.
>>>>
>>>> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
>>>> ---
>>>> V4: bail out in case of usbback_is_loaded() error as requested by
>>>>     Chun Yan Liu
>>>> ---
>>> [...]
>>>>  /* Add usbctrl information to xenstore.
>>>>   *
>>>> - * Adding a usb controller will add a new 'vusb' device in xenstore, and
>>>> - * add corresponding frontend, backend information to it. According to
>>>> - * "update_json", decide wether to update json config file.
>>>> + * Adding a usb controller will add a new 'qusb' or 'vusb' device in 
>>>> xenstore,
>>>> + * and add corresponding frontend, backend information to it. According to
>>>> + * "update_json", decide whether to update json config file.
>>>>   */
>>>>  static int libxl__device_usbctrl_add_xenstore(libxl__gc *gc, uint32_t 
>>>> domid,
>>>>                                                libxl_device_usbctrl 
>>>> *usbctrl,
>>>> @@ -121,6 +144,15 @@ static int 
>>>> libxl__device_usbctrl_add_xenstore(libxl__gc *gc, uint32_t domid,
>>>>  
>>>>          DEVICE_ADD(usbctrl, usbctrls, domid, &usbctrl_saved,
>>>>                     COMPARE_USBCTRL, &d_config);
>>>> +
>>>> +        if (usbctrl->type == LIBXL_USBCTRL_TYPE_QUSB) {
>>>> +            if (!libxl__query_qemu_backend(gc, domid, 
>>>> usbctrl->backend_domid,
>>>> +                                           "qusb", false)) {
>>>
>>> This needs to be sorted out.
>>
>> What do you mean?
>>
>>> And this is maybe a rather dumb question: the xenstore paths for qusb
>>> and kernel backend are the same? What is the likelihood that one
>>> deviates from the other? Note that this is not suggesting that you
>>> over-engineer current code, it's just something that needs clarifying.
>>
>> There is an existing pvusb kernel backend implementation in kernel-xen
>> of openSUSE and SLE. The port of that implementation hasn't been
>> accepted in Linux upstream as it was regarded to fit better in qemu.
>>
>> So the qemu base backend is designed in a way to be compatible to the
>> already existing kernel backend. Future enhancements will be made on the
>> qemu based backend only (as far as SUSE is involved).
>>
>> So the frontend related Xenstore paths are the same, while the backend
>> paths are different ("vusb" vs. "qusb"). And yes, I've tested the same
>> domU with both backends.
>>
> 
> I forgot to ask -- When you repost, can you add such information to
> commit message? Thanks.

Sure.


Juergen


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