Re: [libvirt] PATCH: Support setting a disk drive serial (number)

On Mon, Aug 17, 2009 at 02:37:48PM -0400, Dave Allan wrote: > Daniel P. Berrange wrote: >> All hard disks (IDE, SCSI, USB, VirtIO) have a concept of a serial number >> which is intended to uniquely identify them. If you mean this off, QEMU >> just makes up a serial on the fly. THis is not guarenteed to be stable >> across guest reboots with hardware changes. It is thus desirable to be >> able to specify this in libvirt XML. To that end, this patch allows >> for a <serial> element inside a disk >> >> <disk type='file' device='disk'> >> <source >> file='/media/lacie-500-disk-2/virtual-machines/scratch5.img'/> >> <target dev='vda' bus='virtio'/> >> <serial>dan123virtio</serial> >> </disk> >> >> the contents is free-form. It implemenmts this for the QEMU driver for >> any disk using -drive style args. Unfortunately this excludes USB disk, >> even though internally QEMU can set a serial for these, the -usbdevice >> syntax does not allow it >> >> Daniel >> >> * docs/schemas/domain.rng: Add <serial> element to disks >> * src/domain_conf.h, src/domain_conf.c: XML parsing and >> formatting for disk serial numbers >> * src/qemu_conf.c: Set serial number when launching guests >> * tests/qemuxml2argvdata/qemuxml2argv-disk-drive-shared.args, >> tests/qemuxml2argvdata/qemuxml2argv-disk-drive-shared.xml: Add >> serial number to XML test [snip] > This patch seems like a very good idea to me. I'm surprised it doesn't > cause more grief if the serial # keeps changing. I didn't review the > code too closely, but a definite ACK to the functionality, and I saw no > problems with the implementation in the quick look I took. Well it causes grief for Windows guests with WHQL'd virtio drivers I believe. We've probably just been fortunate with Linux guests that not much functional stuff is based off the serial number. The serial number is used for /dev/disk/by-id symlinks, but most distros use /dev/disk/by-uuid symlinks for mounting volume instead and that's based off a filesystem level UUID, instead of block device level serial.

> As a possible additional feature, in the case of an entire device being > assigned to the guest, have you considered passing through the serial of > the underlying device? The serial is available in the nodedev XML. That's a policy decision, and so not within scope of libvirt. Of course the application provisioning a new guest can see the host device's serial, and copy that across to the guest XML it uses if desired.