1 2qemu usb storage emulation 3-------------------------- 4 5QEMU has three devices for usb storage emulation. 6 7Number one emulates the classic bulk-only transport protocol which is 8used by 99% of the usb sticks on the market today and is called 9"usb-storage". Usage (hooking up to xhci, other host controllers work 10too): 11 12 qemu ${other_vm_args} \ 13 -drive if=none,id=stick,file=/path/to/file.img \ 14 -device nec-usb-xhci,id=xhci \ 15 -device usb-storage,bus=xhci.0,drive=stick 16 17 18Number two is the newer usb attached scsi transport. This one doesn't 19automagically create a scsi disk, so you have to explicitly attach one 20manually. Multiple logical units are supported. Here is an example 21with tree logical units: 22 23 qemu ${other_vm_args} \ 24 -drive if=none,id=uas-disk1,file=/path/to/file1.img \ 25 -drive if=none,id=uas-disk2,file=/path/to/file2.img \ 26 -drive if=none,id=uas-cdrom,media=cdrom,file=/path/to/image.iso \ 27 -device nec-usb-xhci,id=xhci \ 28 -device usb-uas,id=uas,bus=xhci.0 \ 29 -device scsi-hd,bus=uas.0,scsi-id=0,lun=0,drive=uas-disk1 \ 30 -device scsi-hd,bus=uas.0,scsi-id=0,lun=1,drive=uas-disk2 \ 31 -device scsi-cd,bus=uas.0,scsi-id=0,lun=5,drive=uas-cdrom 32 33 34Number three emulates the classic bulk-only transport protocol too. 35It's called "usb-bot". It shares most code with "usb-storage", and 36the guest will not be able to see the difference. The qemu command 37line interface is similar to usb-uas though, i.e. no automatic scsi 38disk creation. It also features support for up to 16 LUNs. The LUN 39numbers must be continuous, i.e. for three devices you must use 0+1+2. 40The 0+1+5 numbering from the "usb-uas" example isn't going to work 41with "usb-bot". 42 43Starting with qemu version 2.7 usb-bot and usb-uas devices can be 44hotplugged. In the hotplug case they are added with "attached = 45false" so the guest will not see the device until the "attached" 46property is explicitly set to true. That allows to attach one or more 47scsi devices before making the device visible to the guest, i.e. the 48workflow looks like this: 49 50 (1) device-add usb-bot,id=foo 51 (2) device-add scsi-{hd,cd},bus=foo.0,lun=0 52 (2b) optionally add more devices (luns 1 ... 15). 53 (3) scripts/qmp/qom-set foo.attached = true 54 55enjoy, 56 Gerd 57 58-- 59Gerd Hoffmann <kraxel@redhat.com> 60