Re: [Xen-users] Attaching dom0 external USB HD to domU

[George Dunlap <dunlapg@xxxxxxxxx>]

On Wed, Mar 21, 2018 at 3:01 PM, John Naggets <hostingnuggets@xxxxxxxxx> wrote:
> On Tue, Mar 20, 2018 at 12:27 PM, George Dunlap <dunlapg@xxxxxxxxx> wrote:
>> It should work, with the following caveats:
>>
>> 1. Your guest OS won't know that it's a removable device, and so may
>> not be as aggressive about flushing data out to it to avoid data loss
>> in the case of unexpected force removal.
>> 2. The device name (/dev/sdf) may not be stable: that is, every time
>> you remove or insert the device, or every time you reboot, you might
>> get a different device name, so you'll need to change the config file.
>> (Or alternately, create a custom udev rule that would recognize that
>> particular USB device and give it a consistent name.)
>
> Thanks George for confirming and for your tips regarding that setup.
>
>> If you're using an HVM guest, and have a new enough version of Xen to
>> have the 'usbdevice' directive, you can use the "bus.addr" naming
>> scheme, which should (I believe) be consistent across both device
>> removal and across reboots (as long as you always plug it into the
>> same slot); but that does mean restricting your guest type, as well as
>> emulating a USB controller and so on, which could potentially be less
>> efficient.
>
> This is actually the case, I am using HVM for a Win2k12r2 domU. So do
> I understand you correctly that the only thing I need in my domU cfg
> file is the following:
>
> usb=1
> usbdevice=[ "host:1.4" ]
>
> In that case let's say lsusb showed my external USB disk plugged in on
> bus 001 and device 004.
>
> By the way I am using Xen 4.9 on Ubuntu 17.10.

Yes, that's the right format.

But you know, I think I may be remembering incorrectly -- I think the
"bus.dev" number increments each time you plug and unplug it.  We
*wanted* to have an interface that allowed you to specify the exact
place in the topology but I think we never got around to it. :-/

Probably the easiest way to check would be to lspci, remove &
re-insert the device, and lspci again.

 -George

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