[fedora-virt] USB passthrough stopped working

[Kashyap Chamarthy]

On Fri, Aug 22, 2014 at 01:18:51PM +0200, VISEUR Eric wrote:
> Hi,
> 
> Sorry, forgot that bit.  Guess holidays made me lose some habits :)
> 
> QEMU: 2.1.0-4.fc20
> Libvirt: 1.2.7-2.fc20
> Virt-manager: 1.0.1-3.fc20
> 
> All from the fedora-virt-preview repo.

Hmm, I just tested and I could reproduce what you're seeing, with these
versions:

  $ rpm -q qemu libvirt; uname -r
  qemu-2.1.0-5.fc22.x86_64
  libvirt-1.2.7-2.fc22.x86_64
  3.15.6-200.fc20.x86_64

That's my USB device on host:

  $ lsusb | grep SanDisk
  Bus 001 Device 037: ID 0781:5567 SanDisk Corp. Cruzer Blade

I could see the USB device listed in the guest XML:

  $ virsh dumpxml f20vm | grep -i hostdev
      <hostdev mode='subsystem' type='usb' managed='yes'>
        <alias name='hostdev0'/>
      </hostdev>

>From the guest log:

  $ tail /var/log/libvirt/qemu/f20vm.log
    libusb: error [_get_usbfs_fd] libusb couldn't open USB device
    /dev/bus/usb/001/037: Permission denied

Check the device file owner:

  $ ls -lsrt /dev/bus/usb/001/037
  0 crw-rw-r--. 1 root root 189, 36 Aug 23 11:01 /dev/bus/usb/001/037

Just to test, I changed the device's owner to QEMU:

  $ chown qemu: /dev/bus/usb/001/037
  $ ls -lZ /dev/bus/usb/001/037
  crw-rw-r--. qemu qemu system_u:object_r:usb_device_t:s0
  /dev/bus/usb/001/037

Then remove the USB device from virt-manager, and re-add it (and check
the device permission again that it reflects QEMU), I see the same error
in the guest log. (SELinux was in permissive.)

Still have to investigate further, though.

--
/kashyap


> -----Original Message-----
> From: Kashyap Chamarthy [mailto:kchamart at redhat.com] 
> Sent: 22 August, 2014 12:09
> To: VISEUR Eric
> Cc: virt at lists.fedoraproject.org
> Subject: Re: [fedora-virt] USB passthrough stopped working
> 
> On Fri, Aug 22, 2014 at 11:27:55AM +0200, VISEUR Eric wrote:
> > Hi,
> > 
> > I've just reinstalled a computer with F20 and virt-preview and noticed 
> > USB passthrough doesn't work with QEMU/KVM.  I add the device using 
> > virt-manager.
> 
> No direct answer to your question, but explicitly spelling out versions of QEMU, libvirt and virt-manager will be useful for anyone who wants to reproduce your issue.
> 
> > 
> > 
> > ·         The device indeed appears in the XML declaration after I add
> > it;
> > 
> > ·         Qemu instances are created under the qemu user;
> > 
> > ·         Qemu.conf wasn't modified;
> > 
> > ·         The device remains owned by root;
> > 
> > ·         The VM libvirt log signals a libusb error: libusb requires
> > write access to USB device nodes.
> > 
> > Is it a known problem ?
> >