Archipelago » qemu

qemu usb storage emulation

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QEMU has three devices for usb storage emulation.

Number one emulates the classic bulk-only transport protocol which is

used by 99% of the usb sticks on the marked today and is called

"usb-storage".  Usage (hooking up to xhci, other host controllers work

too):

  qemu ${other_vm_args}                                \

       -drive if=none,id=stick,file=/path/to/file.img  \

       -device nec-usb-xhci,id=xhci                    \

       -device usb-storage,bus=xhci.0,drive=stick

Number two is the newer usb attached scsi transport.  This one doesn't

automagically create a scsi disk, so you have to explicitly attach one

manually.  Multiple logical units are supported.  Here is an example

with tree logical units:

  qemu ${other_vm_args}                                                \

       -drive if=none,id=uas-disk1,file=/path/to/file1.img             \

       -drive if=none,id=uas-disk2,file=/path/to/file2.img             \

       -drive if=none,id=uas-cdrom,media=cdrom,file=/path/to/image.iso \

       -device nec-usb-xhci,id=xhci                                    \

       -device usb-uas,id=uas,bus=xhci.0                               \

       -device scsi-hd,bus=uas.0,scsi-id=0,lun=0,drive=uas-disk1       \

       -device scsi-hd,bus=uas.0,scsi-id=0,lun=1,drive=uas-disk2       \

       -device scsi-cd,bus=uas.0,scsi-id=0,lun=5,drive=uas-cdrom

Number three emulates the classic bulk-only transport protocol too.

It's called "usb-bot".  It shares most code with "usb-storage", and

the guest will not be able to see the difference.  The qemu command

line interface is simliar to usb-uas though, i.e. no automatic scsi

disk creation.  It also features support for up to 16 LUNs.  The LUN

numbers must be continous, i.e. for three devices you must use 0+1+2.

The 0+1+5 numbering from the "usb-uas" example isn't going to work

with "usb-bot".

enjoy,

  Gerd

--

Gerd Hoffmann <kraxel@redhat.com>