On Fri, Oct 17, 2025 at 08:36:41AM +0200, Eugenio Perez Martin wrote: > On Thu, Oct 16, 2025 at 8:25 AM Eugenio Perez Martin > <[email protected]> wrote: > > > > On Thu, Oct 16, 2025 at 8:22 AM Michael S. Tsirkin <[email protected]> wrote: > > > > > > On Thu, Oct 16, 2025 at 02:03:57PM +0800, Jason Wang wrote: > > > > On Thu, Oct 16, 2025 at 1:45 PM Michael S. Tsirkin <[email protected]> > > > > wrote: > > > > > > > > > > On Thu, Oct 16, 2025 at 01:39:58PM +0800, Jason Wang wrote: > > > > > > > > > > > > > > > > Not exactly bufferize, record. E.g. we do not need to send > > > > > > > > 100 messages to enable/disable promisc mode - together they > > > > > > > > have no effect. > > > > > > > > > > > > Note that there's a case that multiple commands need to be sent, e.g > > > > > > set rx mode. And assuming not all the commands are the best effort, > > > > > > kernel VDUSE still needs to wait for the usersapce at least for a > > > > > > while. > > > > > > > > > > Not wait, record. Generate 1st command, after userspace consumed it - > > > > > generate and send second command and so on. > > > > > > > > Right, that's what I asked in another thread, we still need a timeout > > > > here. > > > > > > we do not need a timeout. > > > > > > > Then I think it would not be too much difference whether it is > > > > VDUSE or CVQ that will fail or break the device. Conceptually, VDUSE > > > > can only advertise NEEDS_RESET since it's a device implementation. > > > > VDUSE can not simply break the device as it requires synchronization > > > > which is not easy. > > > > > > > > > But for each bit of data, at most one command has to be sent, > > > > > we do not care if guest tweaked rx mode 3 times, we only care about > > > > > the latest state. > > > > > > > > Yes, but I want to know what's best when VDUSE meets userspace timeout. > > > > > > > > Thanks > > > > > > > > > userspace should manage its own timeouts. > > > > > > > Can we just apply the patch 2/2 of this RFC directly and apply the > > VDUSE CVQ on top then? What are we missing to do it? > > > > Even better, can we just revert commit 56e71885b0349 ("vduse: > Temporarily fail if control queue feature requested") ?
No because both would let userspace hang kernels merely by not consuming buffers. -- MST
