On Fri, Oct 17, 2025 at 9:21 AM Eugenio Perez Martin <[email protected]> wrote: > > On Fri, Oct 17, 2025 at 8:39 AM Michael S. Tsirkin <[email protected]> wrote: > > > > 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. > > > > My understanding was that you want to be able to debug qemu with gdb > from that hang [1]. > > Could you put an example of the whole chain of events you expect? From > the moment the driver sends a VIRTIO_NET_CTRL_MQ_VQ_PAIRS_SET command, > the VDUSE CVQ Forwards the command to the VDUSE device in the > userspace, and then the vduse userland device does not reply. > > How does the VDUSE CVQ detect that the VDUSE device implemented in > userland does not reply? What are the next steps from that point of > the kernel VDUSE module? > > Thanks! >
Friendly ping!
