Re: [libvirt] [RFC PATCH] qemu: Shorten SCSI hostdev alias to avoid QEMU failure

The alias for hostdevs of type SCSI can be too long for QEMU if larger LUNs are encountered. Here's a real life example: <hostdev mode='subsystem' type='scsi' managed='no'> <source> <adapter name='scsi_host0'/> <address bus='0' target='19' unit='1088634913'/> </source> <address type='drive' controller='0' bus='0' target='0' unit='0'/> </hostdev> this results in a too long drive id, resulting in QEMU yelling Property 'scsi-generic.drive' can't find value 'drive-hostdev-scsi_host0-0-19-1088634913' This commit changes the alias back to the default hostdev$(index) scheme. Signed-off-by: Viktor Mihajlovski <mihajlov(a)linux.vnet.ibm.com&gt; --- Actually this is highlighting a larger issue. Apparently QEMU ids are limited to a length of 32 bytes. This means that SCSI based drives are also in danger to exceed this limit. We should consider to use a drive index for controller-attached disks for alias generation instead of the verbose drive-$bustype-$busaddress schema.

src/qemu/qemu_command.c | 10 +--------- .../qemuxml2argv-hostdev-scsi-boot.args | 4 ++-- .../qemuxml2argv-hostdev-scsi-lsi.args | 4 ++-- .../qemuxml2argv-hostdev-scsi-readonly.args | 4 ++-- .../qemuxml2argv-hostdev-scsi-virtio-scsi.args | 4 ++-- 5 files changed, 9 insertions(+), 17 deletions(-) diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c index 879aed8..8c8bef2 100644 --- a/src/qemu/qemu_command.c +++ b/src/qemu/qemu_command.c @@ -818,16 +818,8 @@ qemuAssignDeviceHostdevAlias(virDomainDefPtr def, virDomainHostdevDefPtr hostdev } } - if (hostdev->source.subsys.type == VIR_DOMAIN_HOSTDEV_SUBSYS_TYPE_SCSI) { - if (virAsprintf(&hostdev->info->alias, "hostdev-%s-%d-%d-%d", - hostdev->source.subsys.u.scsi.adapter, - hostdev->source.subsys.u.scsi.bus, - hostdev->source.subsys.u.scsi.target, - hostdev->source.subsys.u.scsi.unit) < 0) - return -1; - } else if (virAsprintf(&hostdev->info->alias, "hostdev%d", idx) < 0) { + if (virAsprintf(&hostdev->info->alias, "hostdev%d", idx) < 0) return -1; - } return 0; }