> On 2015/10/16 21:52, Bruce Richardson wrote: > > On Mon, Aug 31, 2015 at 12:55:26PM +0900, Tetsuya Mukawa wrote: > >> The patch introduces a new PMD. This PMD is implemented as thin > wrapper > >> of librte_vhost. It means librte_vhost is also needed to compile the PMD. > >> The PMD can have 'iface' parameter like below to specify a path to > connect > >> to a virtio-net device. > >> > >> $ ./testpmd -c f -n 4 --vdev 'eth_vhost0,iface=/tmp/sock0' -- -i > >> > >> To connect above testpmd, here is qemu command example. > >> > >> $ qemu-system-x86_64 \ > >> <snip> > >> -chardev socket,id=chr0,path=/tmp/sock0 \ > >> -netdev vhost-user,id=net0,chardev=chr0,vhostforce \ > >> -device virtio-net-pci,netdev=net0 > >> > >> Signed-off-by: Tetsuya Mukawa <mukawa at igel.co.jp> > > With this PMD in place, is there any need to keep the existing vhost library > > around as a separate entity? Can the existing library be > subsumed/converted into > > a standard PMD? > > > > /Bruce > > Hi Bruce, > > I concern about whether the PMD has all features of librte_vhost, > because librte_vhost provides more features and freedom than ethdev API > provides. > In some cases, user needs to choose limited implementation without > librte_vhost. > I am going to eliminate such cases while implementing the PMD. > But I don't have strong belief that we can remove librte_vhost now. > > So how about keeping current separation in next DPDK? > I guess people will try to replace librte_vhost to vhost PMD, because > apparently using ethdev APIs will be useful in many cases. > And we will get feedbacks like "vhost PMD needs to support like this usage". > (Or we will not have feedbacks, but it's also OK.) > Then, we will be able to merge librte_vhost and vhost PMD.
I agree with the above. One the concerns I had when reviewing the patch was that the PMD removes some freedom that is available with the library. Eg. Ability to implement the new_device and destroy_device callbacks. If using the PMD you are constrained to the implementations of these in the PMD driver, but if using librte_vhost, you can implement your own with whatever functionality you like - a good example of this can be seen in the vhost sample app. On the other hand, the PMD is useful in that it removes a lot of complexity for the user and may work for some more general use cases. So I would be in favour of having both options available too. Ciara > > Thanks, > Tetsuya
