On Sat, Oct 15, 2022 at 08:36:19PM -0400, Peter Geis wrote: > On Wed, Oct 12, 2022 at 5:14 PM Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: > > > > There's one other thing you might try, although I'm not sure that it > > will provide any useful new information. Instead of collecting a > > usbmon trace, collect a usbfs snoop log. Before starting qemu, do: > > > > echo 1 >/sys/module/usbcore/parameters/usbfs_snoop > > > > This will cause the accesses performed via usbfs, including those > > performed by the qemu process, to be printed in the kernel log. (Not > > all of the accesses, but the more important ones.) Let's see what shows > > up. > > So I built and tested the newest version of QEMU, and it exhibits the > same issue. I've also captured the log as requested and attached it > here. Here's what appears to be the relevant parts of the log. > [93190.933026] usb 3-6.2: opened by process 149607: rpc-libvirtd > [93191.006429] usb 3-6.2: opened by process 149605: qemu-system-x86 The device is opened by proces 194605, which is probably the main qemu process (or the main one in charge of USB I/O). I assume this is the process which goes ahead with initialization and enumeration, because there are no indications of other processes opening the device. > [93195.712484] usb 3-6.2: usbdev_do_ioctl: RESET > [93195.892482] usb 3-6.2: reset full-speed USB device number 70 using xhci_hcd > [93196.095050] cdc_acm 3-6.2:1.0: ttyACM0: USB ACM device As part of initialization, qemu resets the device and its interfaces then get claimed by the cdc_acm driver on the host. This may be the problem; there's no indication in the log that cdc_acm ever releases those interfaces. > [93196.482584] usb 3-6.2: usbdev_do_ioctl: SUBMITURB > [93196.482589] usb 3-6.2: usbfs: process 149617 (CPU 3/KVM) did not claim interface 0 before use > [93209.729484] usb 3-6.2: usbdev_do_ioctl: SUBMITURB > [93209.729489] usb 3-6.2: usbfs: process 149616 (CPU 2/KVM) did not claim interface 0 before use > [93209.729574] usb 3-6.2: usbdev_do_ioctl: CLEAR_HALT > [93209.729577] usb 3-6.2: usbfs: process 149617 (CPU 3/KVM) did not claim interface 1 before use > [93209.729632] usb 3-6.2: usbdev_do_ioctl: SUBMITURB > [93209.729635] usb 3-6.2: usbfs: process 149614 (CPU 0/KVM) did not claim interface 0 before use Unforunately these warning messages don't indicate directly whether the attempts to use the interfaces were successful. But it's clear that something went wrong with those URB submissions because the snoop log doesn't include the contents of the URBs or their results. My guess is that the attempts failed because the interfaces were already claimed by cdc_acm in the host. I would expect qemu to unbind cdc_acm when it starts up, but apparently it doesn't. And there are no CLAIM_PORT messages in the log. Perhaps it will help if you do the unbind by hand before starting qemu. Try doing: echo 3-6.2:1.0 >/sys/bus/usb/drivers/cdc_acm/unbind echo 3-6.2:1.1 >/sys/bus/usb/drivers/cdc_acm/unbind Or better yet, blacklist the cdc_acm driver on the host if you can. Alan Stern
