On Mon, Oct 10, 2022 at 10:22:55AM -0400, Peter Geis wrote: > On Mon, Oct 10, 2022 at 10:07 AM Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: > > > > On Mon, Oct 10, 2022 at 09:56:53AM -0400, Peter Geis wrote: > > > Good Morning, > > > > > > I've run into a bug with a new usb device when attempting to pass > > > through using qemu-kvm. Another device is passed through without > > > issue, and qemu spice passthrough does not exhibit the issue. The usb > > > device shows up in the KVM machine, but is unusable. I'm unsure if > > > this is a usbfs bug, a qemu bug, or a bug in the device driver. > > > > > > usb 3-6.2: usbfs: process 365671 (CPU 2/KVM) did not claim interface 0 > > > before use > > > usb 3-6.2: usbfs: process 365671 (CPU 2/KVM) did not claim interface 0 > > > before use > > > usb 3-6.2: usbfs: process 365672 (CPU 3/KVM) did not claim interface 1 > > > before use > > > usb 3-6.2: usbfs: process 365671 (CPU 2/KVM) did not claim interface 0 > > > before use > > > usb 3-6.2: usbfs: process 365672 (CPU 3/KVM) did not claim interface 0 > > > before use > > > usb 3-6.2: usbfs: process 365672 (CPU 3/KVM) did not claim interface 0 > > > before use > > > > These are warnings, not bugs, although one could claim that the warnings > > are caused by a bug in qemu-kvm. > > The bug is the device is unusable in passthrough, this is the only > direction as to why. The question is which piece of software is > causing it. I figure qemu is the most likely suspect, but they request > bugs that are possibly in kvm start here. The cdc-acm driver is the > least likely in my mind, as the other device that works also uses it. > I just tested removing the other working device and only passing > through the suspect device, and it still triggers the bug. So whatever > the problem is, it's specific to this one device. Does anything of interest about the device show up in the virtual machine's kernel log? You can collect a usbmon trace on the host system to gather more information about what the virtual machine is trying to do. Your previous post shows that the device is on bus 3, so before starting qemu-kvm you would do: cat /sys/kernel/debug/usb/usbmon/3u >mon.txt in a separate window. Kill the cat process when the test is over and post the output file. It'll help if you unplug the working device (and in fact as many devices on bus 3 as is practical) before running the test, so that the trace includes only traffic to the non-working device. For comparison, you could also acquire a usbmon trace of what happens when you try using the device on a real, non-virtual machine. For this test you would start the trace before plugging in the device. Alan Stern
