On Thu, 14 Jan 2021 at 23:17, Alex Bennée <alex.ben...@linaro.org> wrote:
> > Shreyansh Chouhan <chouhan.shreyansh2...@gmail.com> writes: > > > Just an update: > > > > I've studied the virtio specification along with the source code and I > now > > understand what the device implementation is > > going to look like. Also I understand the source code a lot better. I am > > now reading about the qemu vhost-user protocol. > > > > Although I haven't read about the vhost-user daemon in detail, from what > > little I have read, I would say that the daemon > > would get the virtqueues from the virtio device and forward it to the > sound > > device of the host. (This is the hard part > > I think, since an in QEMU device would use code already written for > > processing these queues.) > > I can't comment on the difficulty there but this does point more towards > using the in-QEMU approach given we have a bunch of utility functions > already. > > > I think only the tx and rx > > queues would be shared, and although I do not know exactly how the > sharing > > will be implemented, I think the memory > > will be shared to the vhost-user daemon too? So now the virtqueue memory > is > > shared between the virtio driver in guest > > OS, the virtio device in QEMU, and the vhost-user daemon running in the > > host userspace. > > QEMU uses a memfd file descriptor to share the guests entire memory map > with the daemon. > Oh I see. > > > As for the configuration part, the driver will negotiate features with > the > > virtio device in QEMU, which in turn will communicate > > with the vhost-user daemon (via sockets) to get the features supported I > > think. > > > > This is what I think it will roughly look like. (Of course modulo the > > implementation details.) I do not yet understand how > > much more difficult will implementing the vhost-user daemon be, and > since I > > was already > > warned about the difficulty, I will not risk making any hasty decisions > > that later hinder the project. I will read up > > about the vhost-user daemon and how it's implemented to get a better > idea, > > and then make the final call. > > If you want to see an example of a branch new vhost-user daemon being > built up from scratch see my recent virtio-rpmb series. The first few > patches of in-QEMU code will be the same boilerplate either way I think: > > https://patchew.org/QEMU/20200925125147.26943-1-alex.ben...@linaro.org/ This looks super helpful! Thanks a lot for this. > > > > Anyways I am super excited about the project. I got to learn about some > > really cool things in the past couple of days, > > and I can not wait to implement it. :) > > > -- > Alex Bennée > - Shreyansh Chouhan
