On 05/28/2015 02:28 PM, Michal Privoznik wrote: > 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 <pagu...@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?
Without this patch, it works with normal virtio-net drivers but may not work for guest pmd. Since pmd does not use MSI-X interrupts, so qemu won't start vhost_net. So libvirt needs vhostforce for vhost-user. With this patch, libvirt does not need to care about this. > > Michal >
