----- Original Message ----- From: "Daniel P. Berrange" <berrange@xxxxxxxxxx> To: "Guannan Ren" <gren@xxxxxxxxxx> Cc: libvir-list@xxxxxxxxxx Sent: Tuesday, September 3, 2013 5:38:08 AM Subject: Re: [PATCH 0/5]qemu: add usb-bot scsi controller support On Mon, Sep 02, 2013 at 05:38:39PM +0800, Guannan Ren wrote: >> >> BZ:https://bugzilla.redhat.com/show_bug.cgi?id=917702 >> qemu patch:http://lists.gnu.org/archive/html/qemu-devel/2013-01/msg02200.html >> >> These patch aims to add usb-bot SCSI controller support for libvirt. >> As usb-storage libvirt already supported, usb-bot only supports one >> SCSI target with SCSI ID 0. >> The difference is that usb-storage creates SCSI HBA and additionaly >> either a scsi-disk or a scsi-generic device, usb-bot only creates the >> SCSI HBA. we can attach a SCSI device to it with another -device. >> >> usb-bot supports a single target and a number of luns. The limit is >> 15 luns (0~15 LUN ID) and they must be contiguous(using lun 0 and 2 >> without 1 doesn't work). >> >> Athought usb-bot is a SCSI controller it needs to be attached to a >> exsiting USB controller for work. So it has to use address of usb type. >> >> Libvirt XML: >> >> <devices> >> ... >> <disk type='file' device='disk'> >> <driver name='qemu' type='raw'/> >> <source file='/var/lib/libvirt/images/disk.qcow2'/> >> <target dev='sdc' bus='scsi'/> >> <address type='drive' controller='0' bus='0' target='0' unit='0'/> >> </disk> >> <controller type='usb' index='0'/> >> <controller type='scsi' index='0' model='usb-bot'> >> <address type='usb' bus='0' port='1'/> >> </controller> >> ... >> </devices> > How does this work from a hotplug POV. With usb-storage you could > just hotplug the <disk> device. Now it seems we need two separate > hotplug calls one of the <controller> and one for the <disk> and >the reverse. Yes, I will think about the hotplug. >> >> The QEMU commandline: >> >> qemu ${other_vm_args} \ >> -device piix3-usb-uhci,id=usb \ >> -device usb-bot,id=scsi0,bus=usb.0,port=1 \ >> -drive file=/var/lib/libvirt/images/disk.qcow2,if=none,id=drive-scsi0-0-0-0,format=raw \ >> -device scsi-hd,bus=scsi0.0,channel=0,scsi-id=0,lun=0,drive=drive-scsi0-0-0-0,id=scsi0-0-0-0 >> >> As the usb-storage creates scsi disk automatically which doesn't let >> you set scsi-disk properties such as vendor, product, wwn, channel, >> scsi-id and lun. So QEMU guys prefer usb-bot to usb-storage. >> So this is the first part of the whole work. Next step will replace >> usb-storage with usb-bot when disk in xml uses usb bus like >> <disk ...> >> <...> >> <target bus='usb'> >> </disk> > I'm not really a fan of introducing 2 different ways to configure > the exact same device. The idea is to use usb-bot instead of usb-storage in this case if usb-bot capability is available. usb-storage automatically expands into two devices, a SCSI controller and a SCSI device. And user cannot set any property values to this SCSI device such as vendor, product, wwn, channel, scsi-id and lun. usb-bot gives the more flexible configurations. I think it is to use usb-bot if usb-bot is supported, otherwise still use usb-storage. The xml will not change at all. Guannan -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list