We have previously effectively ignored all <controller type='ide'>
elements in a domain definition.
On the i440fx-based machinetypes there is an IDE controller that is
included in the chipset and can't be removed (which is the ide
controller with index='0'>), so it makes sense to ignore that one
controller. However, if an i440fx domain definition has a 2nd
controller, nothing catches this error (unless you also have a disk
attached to it, in which case qemu will complain that you're trying to
use the ide controller named "ide1", which doesn't exist), and if any
other type of domain has even a single controller defined, it will be
incorrectly ignored.
Ignoring a bogus controller definition isn't such a big problem, as
long as an error is logged when any disk is attached to that
non-existent controller. But in the case of q35-based machinetypes,
the hardcoded id ("alias" in libvirt terms) of its builtin SATA
controller is "ide", which happens to be the same id as the builtin
IDE controller on i440fx machinetypes. So libvirt creates a
commandline believing that it is connecting the disk to the builtin
(but actually nonexistent) IDE controller, qemu thinks that libvirt
wanted that disk connected to the builtin SATA controller, and
everybody is happy.
Until you try to connect a 2nd disk to the IDE controller. Then qemu
will complain that you're trying to set unit=1 on a controller that
requires unit=0 (SATA controllers are organized differently than IDE
controllers).
After this patch, if a domain has an IDE controller defined for a
machinetype that has no IDE controllers, libvirt will log an error
about the controller itself as it is building the qemu commandline
(rather than a (possible) error from qemu about disks attached to that
controller). This is done by adding IDE to the list of controller
types that are handled in the loop that creates controller command
strings in qemuBuildCommandline() (previously it would *always* skip
IDE controllers). Then qemuBuildControllerDevStr() is modified to log
an appropriate error in the case of IDE controllers.
In the future, if we add support for extra IDE controllers (piix3-ide
and/or piix4-ide) we can just add it into the IDE case in
qemuBuildControllerDevStr(). For now, nobody seems anxious to add
extra support for an aging and very slow controller, when there are so
many better options available.
Resolves:
https://bugzilla.redhat.com/show_bug.cgi?id=1176071 (Fedora)
https://bugzilla.redhat.com/show_bug.cgi?id=1142631
This patch resolves a situation where the same "<target dev='$name'...>"
can be used for multiple disks in the domain.
While the $name is "mostly" advisory regarding the expected order that
the disk is added to the domain and not guaranteed to map to the device
name in the guest OS, it still should be unique enough such that other
domblk* type operations can be performed.
Without the patch, the domblklist will list the same Target twice:
$ virsh domblklist $dom
Target Source
------------------------------------------------
sda /var/lib/libvirt/images/file.qcow2
sda /var/lib/libvirt/images/file.img
Additionally, getting domblkstat, domblkerror, domblkinfo, and other block*
type calls will not be able to reference the second target.
Fortunately, hotplug disallows adding a "third" sda value:
$ qemu-img create -f raw /var/lib/libvirt/images/file2.img 10M
$ virsh attach-disk $dom /var/lib/libvirt/images/file2.img sda
error: Failed to attach disk
error: operation failed: target sda already exists
$
BUT, it since 'sdb' doesn't exist one would get the following on the same
hotplug attempt, but changing to use 'sdb' instead of 'sda'
$ virsh attach-disk $dom /var/lib/libvirt/images/file2.img sdb
error: Failed to attach disk
error: internal error: unable to execute QEMU command 'device_add': Duplicate ID 'scsi0-0-1' for device
$
Since we cannot fix this issue at parsing time, the best that can be done so
as to not "lose" a domain is to make the check prior to starting the guest
with the results as follows:
$ virsh start $dom
error: Failed to start domain $dom
error: XML error: target 'sda' duplicated for disk sources '/var/lib/libvirt/images/file.qcow2' and '/var/lib/libvirt/images/file.img'
$
Running 'make check' found a few more instances in the tests where this
duplicated target dev value was being used. These also exhibited some
duplicated 'id=' values (negating the uniqueness argument of aliases) in
the corresponding .args file and of course the *xmlout version of a few
input XML files.
There are two ways to use a iSCSI LUN as disk source for qemu.
* The LUN's path as it shows up on host, e.g.
/dev/disk/by-path/ip-$ip:3260-iscsi-$iqn-fc18:iscsi.iscsi0-lun-1
* The libiscsi URI from the storage pool source element host attribute, e.g.
iscsi://demo.org:6000/iqn.1992-01.com.example/1
For a "volume" type disk, if the specified "pool" is of iscsi
type, we should support to use the LUN in either of above 2 ways.
That's why to introduce a new XML tag "mode" for the disk source
(libvirt should support iscsi pool with libiscsi, but it's another
new feature, which should be done later).
The "mode" can be either of "host" or "direct". Use "host" to indicate
use of the LUN with the path as it shows up on host. Use "direct" to
indicate to use it with the source pool host URI (future patches may support
to use network type libvirt storage too, e.g. Ceph)
