On Mon, Jun 9, 2025 at 2:11 PM Eugenio Perez Martin <epere...@redhat.com> wrote: > > On Mon, Jun 9, 2025 at 3:50 AM Jason Wang <jasow...@redhat.com> wrote: > > > > On Mon, Jun 9, 2025 at 9:41 AM Jason Wang <jasow...@redhat.com> wrote: > > > > > > On Fri, Jun 6, 2025 at 7:50 PM Eugenio Pérez <epere...@redhat.com> wrote: > > > > > > > > This allows to define all functions checking the API version set by the > > > > userland device. > > > > > > > > Signed-off-by: Eugenio Pérez <epere...@redhat.com> > > > > > > It might be worth clarifying how it works. > > > > > > For example, > > > > > > 1) would VDUSE behave differently or if it's just some new ioctls > > I'd like to test more in-depth, but a device can just bump the version > ID and then implement the replies to the vduse messages. No need to > implement new ioctls. If the VDUSE device sets 0 in either number of > ASID or vq groups, the kernel assumes 1.
Right, this is the way we use now and I think maybe we can document this somewhere. > > But you have a very good point here, I think it is wise to evaluate > the shortcut of these messages in the VDUSE kernel module. If a VDUSE > device only has one vq group and one ASID, it can always return group > 0 and asid 0 for everything, and fail every try to ser asid != 0. Yes, and vhost-vDPA needs to guard against the misconfiguration. > This > way, the update is transparent for the VDUSE device, and future > devices do not need to implement the reply of these. What do you > think? This should work. > > > > 2) If VDUSE behave differently, do we need a ioctl to set the API > > > version for backward compatibility? > > > > Speak too fast, there's a VDUSE_SET_API_VERSION actually. > > > > I think we need to think if it complicates the migration compatibility or > > not. > > > > Do you mean migration as "increase the VDUSE version number", not "VM > live migration from vduse version 0 to vduse version 1", isn't it? The > second should not have any problem but I haven't tested it. I mean if we bump the version, we can't migrate from version 1 to version 0. Or we can offload this to the management (do we need to extend the vdpa tool for this)? Thanks
