Re: [Qemu-devel] [PATCH] net: Remove vhostforce option in addition to vhost parameter

[Michal Privoznik <mprivozn@redhat.com>]

On 28.05.2015 05:36, Jason Wang wrote:
> 
> 
> On 05/28/2015 11:21 AM, Jason Wang wrote:
>>
>> On 05/27/2015 07:57 PM, Michael S. Tsirkin wrote:
>>> On Wed, May 27, 2015 at 04:45:34PM +0800, Jason Wang wrote:
>>>>>
>>>>> On 05/27/2015 02:26 PM, Pankaj Gupta wrote:
>>>>>>> Ping.
>>>>>>>
>>>>>>> Can I get any suggestions on this patch.
>>>>>>>
>>>>>>> Best regards,
>>>>>>> Pankaj
>>>>>>>
>>>>>>>>> vhostforce was added to enable vhost when
>>>>>>>>>  guest don't have MSI-X support.
>>>>>>>>>  Now, we have scenarios like DPDK in Guest which dont use
>>>>>>>>>  interrupts and still use vhost. Also, performance of guests
>>>>>>>>>  without MSI-X support is getting less popular.
>>>>>>>>>
>>>>>>>>>  Its OK to remove this extra option and enable vhost
>>>>>>>>>  on the basis of vhost=ON/OFF.
>>>>>>>>>  Done basic testing with vhost on/off for latest guests
>>>>>>>>>  and old guests(non-msix).
>>>>>>>>>
>>>>>>>>> Signed-off-by: Pankaj Gupta <pagupta@redhat.com>
>>>>> Looks good. Two questions:
>>>>>
>>>>> - Did libvirt use this? if not, we may want to drop vhostfore option
>>>>> completely.
>>> Yes, it did.
>>>
>> For vhost-user, vhostforce is mandatory. But how about tap? Looks like
>> it was not used, and I could not even find any option in
>> http://libvirt.org/formatdomain.html.
>>
> 
> CC Michal for the answer.
> 

No, vhostforce is not used by libvirt at all. Which brings up
interesting question: for vhost-user libvirt constructs merely the
follwing cmd line:

-chardev socket,id=charnet0,path=/tmp/vhost0.sock,server \
-netdev type=vhost-user,id=hostnet0,chardev=charnet0 \

How does vhostforce fit in? I suppose the cmd line is working even
without libvirt passing vhostforce. Should it do so?

Michal