Re: [BUG] KVM USB passthrough did not claim interface before use

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Sat, Oct 15, 2022 at 9:33 PM Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote:
>
> 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.

Good Afternoon,

Thanks, blacklisting cdc_acm stopped usbfs from failing to claim it
again. Unfortunately I ran into another issue, where KVM/QEMU doesn't
claim the USB device again after the device resets. I've encountered
this before with other devices and there doesn't seem to be a way to
resolve it yet. It seems that my issue with this device was a
different manifestation of the same problem, and there currently isn't
a fix for that.

Thank you for your assistance.
Very Respectfully,
Peter

>
> Alan Stern



[Index of Archives]     [KVM ARM]     [KVM ia64]     [KVM ppc]     [Virtualization Tools]     [Spice Development]     [Libvirt]     [Libvirt Users]     [Linux USB Devel]     [Linux Audio Users]     [Yosemite Questions]     [Linux Kernel]     [Linux SCSI]     [XFree86]

  Powered by Linux