The new introduced optional attribute "copy_on_read</code> controls
whether to copy read backing file into the image file. The value can
be either "on" or "off". Copy-on-read avoids accessing the same backing
file sectors repeatedly and is useful when the backing file is over a
slow network. By default copy-on-read is off.

In the past, generic SCSI commands issued from a guest to a virtio
disk were always passed through to the underlying disk by qemu, and
the kernel would also pass them on.

As a result of CVE-2011-4127 (see:
http://seclists.org/oss-sec/2011/q4/536), qemu now honors its
scsi=on|off device option for virtio-blk-pci (which enables/disables
passthrough of generic SCSI commands), and the kernel will only allow
the commands for physical devices (not for partitions or logical
volumes). The default behavior of qemu is still to allow sending
generic SCSI commands to physical disks that are presented to a guest
as virtio-blk-pci devices, but libvirt prefers to disable those
commands in the standard virtio block devices, enabling it only when
specifically requested (hopefully indicating that the requester
understands what they're asking for). For this purpose, a new libvirt
disk device type (device='lun') has been created.

device='lun' is identical to the default device='disk', except that:

1) It is only allowed if bus='virtio', type='block', and the qemu
   version is "new enough" to support it ("new enough" == qemu 0.11 or
   better), otherwise the domain will fail to start and a
   CONFIG_UNSUPPORTED error will be logged).

2) The option "scsi=on" will be added to the -device arg to allow
   SG_IO commands (if device !='lun', "scsi=off" will be added to the
   -device arg so that SG_IO commands are specifically forbidden).

Guests which continue to use disk device='disk' (the default) will no
longer be able to use SG_IO commands on the disk; those that have
their disk device changed to device='lun' will still be able to use SG_IO
commands.

*docs/formatdomain.html.in - document the new device attribute value.
*docs/schemas/domaincommon.rng - allow it in the RNG
*tests/* - update the args of several existing tests to add scsi=off, and
 add one new test that will test scsi=on.
*src/conf/domain_conf.c - update domain XML parser and formatter

*src/qemu/qemu_(command|driver|hotplug).c - treat
 VIR_DOMAIN_DISK_DEVICE_LUN *almost* identically to
 VIR_DOMAIN_DISK_DEVICE_DISK, except as indicated above.

Note that no support for this new device value was added to any
hypervisor drivers other than qemu, because it's unclear what it might
mean (if anything) to those drivers.

We already support CPU features with '.' in their name (e.g., sse4.1) so
we should not forbid that in the schema.

When doing security relabeling, there are cases where a per-file
override might be appropriate.  For example, with a static label
and relabeling, it might be appropriate to skip relabeling on a
particular disk, where the backing file lives on NFS that lacks
the ability to track labeling.  Or with dynamic labeling, it might
be appropriate to use a custom (non-dynamic) label for a disk
specifically intended to be shared across domains.

The new XML resembles the top-level <seclabel>, but with fewer
options (basically relabel='no', or <label>text</label>):

<domain ...>
  ...
  <devices>
    <disk type='file' device='disk'>
      <source file='/path/to/image1'>
        <seclabel relabel='no'/> <!-- override for just this disk -->
      </source>
      ...
    </disk>
    <disk type='file' device='disk'>
      <source file='/path/to/image1'>
        <seclabel relabel='yes'> <!-- override for just this disk -->
          <label>system_u:object_r:shared_content_t:s0</label>
        </seclabel>
      </source>
      ...
    </disk>
    ...
  </devices>
  <seclabel type='dynamic' model='selinux'>
    <baselabel>text</baselabel> <!-- used for all devices without override -->
  </seclabel>
</domain>

This patch only introduces the XML and documentation; future patches
will actually parse and make use of it.  The intent is that we can
further extend things as needed, adding a per-device <seclabel> in
more places (such as the source of a console device), and possibly
allowing a <baselabel> instead of <label> for labeling where we want
to reuse the cNNN,cNNN pair of a dynamically labeled domain but a
different base label.

First suggested by Daniel P. Berrange here:
https://www.redhat.com/archives/libvir-list/2011-December/msg00258.html

* docs/schemas/domaincommon.rng (devSeclabel): New define.
(disk): Use it.
* docs/formatdomain.html.in (elementsDisks, seclabel): Document
the new XML.
* tests/qemuxml2argvdata/qemuxml2argv-seclabel-dynamic-override.xml:
New test, to validate RNG.

The RNG for <seclabel> was too strict - if it was present, then it
had to have sub-elements, even if those didn't make sense for the
given attributes.  Also, we didn't have any tests of <seclabel>
parsing or XML output.

In this patch, I added more parsing tests than output tests (since
the output populates and/or reorders fields not present in certain
inputs).  Making the RNG reliable is a precursor to using <seclabel>
variants in more places in the XML in later patches.

See also:
http://berrange.com/posts/2011/09/29/two-small-improvements-to-svirt-guest-configuration-flexibility-with-kvmlibvirt/

* docs/schemas/domaincommon.rng (seclabel): Tighten rules.
* tests/qemuxml2argvtest.c (mymain): New tests.
* tests/qemuxml2xmltest.c (mymain): Likewise.
* tests/qemuxml2argvdata/qemuxml2argv-seclabel-*.*: New files.

Original patch by Bharata. Updated to use {1,16} in spaprvioReg based
on example from Eric Blake.
Signed-off-by: NBharata B Rao <bharata@linux.vnet.ibm.com>
Signed-off-by: NPrerna Saxena <prerna@linux.vnet.ibm.com>
Signed-off-by: NMichael Ellerman <michael@ellerman.id.au>

In QEMU PPC64 we have a network device called "spapr-vlan". We can specify
this using the existing syntax for network devices, however libvirt
currently rejects "spapr-vlan" in virDomainNetDefParseXML() because of
the "-". Fix the code to accept "-".

* src/conf/domain_conf.c (virDomainNetDefParseXML): Allow '-' in
model name, and be more efficient.
* docs/schemas/domaincommon.rng: Limit valid model names to match code.
Based on a patch by Michael Ellerman.

ppc64 as new arch type and pseries as new machine type are
added under <os> ...  </os>.
Signed-off-by: NBharata B Rao <bharata@linux.vnet.ibm.com>
Signed-off-by: NPrerna Saxena <prerna@linux.vnet.ibm.com>

Enable block I/O throttle for per-disk in XML, as the first
per-disk IO tuning parameter.
Signed-off-by: NLei Li <lilei@linux.vnet.ibm.com>
Signed-off-by: NZhi Yong Wu <wuzhy@linux.vnet.ibm.com>
Signed-off-by: NEric Blake <eblake@redhat.com>

This adds per-device weights to <blkiotune>.  Note that the
cgroups implementation only supports weights per block device,
and not per-file within the device; hence this option must be
global to the domain definition rather than tied to individual
<devices>/<disk> entries:

<domain ...>
  <blkiotune>
    <device>
      <path>/path/to/block</path>
      <weight>1000</weight>
    </device>
  </blkiotune>
..

This patch also adds a parameter --device-weights to virsh command
blkiotune for setting/getting blkiotune.weight_device for any
hypervisor that supports it.  All <device> entries under
<blkiotune> are concatenated into a single string attribute under
virDomain{Get,Set}BlkioParameters, named "device_weight".
Signed-off-by: NHu Tao <hutao@cn.fujitsu.com>
Signed-off-by: NEric Blake <eblake@redhat.com>

virt-xml-validate fails when run on a domain XML file of type 'vbox'.

For failing test case, see https://bugzilla.redhat.com/show_bug.cgi?id=757097

This patch updates the XML schema to accept all valid hypervisor
types, as well as dropping hypervisor types that are not in use
by the current code base.
Signed-off-by: NEric Blake <eblake@redhat.com>

This patch adds XML definitions for guest NUMA specification and contains
routines to parse the same. The guest NUMA specification looks like this:

<cpu>
        ...
        <topology sockets='2' cores='4' threads='2'/>
        <numa>
                <cell cpus='0-7' memory='512000'/>
                <cell cpus='8-15' memory='512000'/>
        </numa>
        ...
</cpu>
Signed-off-by: NBharata B Rao <bharata@linux.vnet.ibm.com>

The types used in domaincommon.rng and secret.rng should be the same.

Move genericName to basictypes.rng, then drop redundant types now
that secret.rng uses basictypes.rng.
Signed-off-by: NJosh Durgin <josh.durgin@dreamhost.com>
Signed-off-by: NEric Blake <eblake@redhat.com>

Add additional fields to let you specify the how to authenticate with a disk.
The secret to use may be referenced by a usage string or a UUID, i.e.:

<auth username='myuser'>
 <secret type='ceph' usage='secretname'/>
</auth>

or

<auth username='myuser'>
 <secret type='ceph' uuid='0a81f5b2-8403-7b23-c8d6-21ccc2f80d6f'/>
</auth>
Signed-off-by: NJosh Durgin <josh.durgin@dreamhost.com>

This attribute says what to do with cdrom (or floppy) if
the source is missing. It accepts:
- mandatory - fail if missing for any reason (the default)
- requisite - fail if missing on boot up, drop if missing on
              migrate/restore/revert
- optional  - drop if missing at any start attempt.

However, this patch introduces only XML part of this new
functionality.

Tested with multiple AHCI controllers and multiple disks attached
to a controller. E.g.,

    <disk type='file' device='disk'>
      <driver name='qemu' type='raw'/>
      <source file='/var/lib/libvirt/images/test/disk0.raw'/>
      <target dev='sda' bus='sata'/>
      <address type='drive' controller='0' bus='0' unit='0'/>
    </disk>
    <disk type='file' device='disk'>
      <driver name='qemu' type='raw'/>
      <source file='/var/lib/libvirt/images/test/disk1.raw'/>
      <target dev='sdb' bus='sata'/>
      <address type='drive' controller='0' bus='0' unit='1'/>
    </disk>
    <disk type='file' device='disk'>
      <driver name='qemu' type='raw'/>
      <source file='/var/lib/libvirt/images/test/disk2.raw'/>
      <target dev='sdc' bus='sata'/>
      <address type='drive' controller='1' bus='0' unit='0'/>
    </disk>
    <controller type='sata' index='0'>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x0'/>
    </controller>
    <controller type='sata' index='1'>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x06' function='0x0'/>
    </controller>

VirtFS allows the user to choose between path/handle based fs driver.
As of now, libvirt hardcoded path based driver only. This patch provides
a solution to allow user to choose between path/handle based fs driver.

Sample:

    <filesystem type='mount'>
      <driver type='handle'/>
      <source dir='/folder/to/share1'/>
      <target dir='mount_tag1'/>
    </filesystem>

    <filesystem type='mount'>
      <driver type='path'/>
      <source dir='/folder/to/share2'/>
      <target dir='mount_tag2'/>
    </filesystem>
Signed-off-by: NHarsh Prateek Bora <harsh@linux.vnet.ibm.com>
Signed-off-by: NEric Blake <eblake@redhat.com>

Previously libvirt's disk device XML only had a single attribute,
error_policy, to control both read and write error policy, but qemu
has separate options for controlling read and write. In one case
(enospc) a policy is allowed for write errors but not read errors.

This patch adds a separate attribute that sets only the read error
policy. If just error_policy is set, it will apply to both read and
write error policy (previous behavior), but if the new rerror_policy
attribute is set, it will override error_policy for read errors only.
Possible values for rerror_policy are "stop", "report", and "ignore"
("report" is the qemu-controlled default for rerror_policy when
error_policy isn't specified).

For consistency, the value "report" has been added to the possible
values for error_policy as well.

When support for was added for PCI multifunction cards (in commit
9f8baf, first included in libvirt 0.9.3), it was done by always
turning on the multifunction bit for all PCI devices. Since that time
it has been realized that this is not an ideal solution, and that the
multifunction bit must be selectively turned on. For example, see

  https://bugzilla.redhat.com/show_bug.cgi?id=728174

and the discussion before and after

  https://www.redhat.com/archives/libvir-list/2011-September/msg01036.html

This patch modifies multifunction support so that the multifunction=on
option is only added to the qemu commandline for a device if its PCI
<address> definition has the attribute "multifunction='on'", e.g.:

  <address type='pci' domain='0x0000' bus='0x00'
           slot='0x04' function='0x0' multifunction='on'/>

In practice, the multifunction bit should only be turned on if
function='0' AND other functions will be used in the same slot - it
usually isn't needed for functions 1-7 (although there are apparently
some exceptions, e.g. the Intel X53 according to the QEMU source
code), and should never be set if only function 0 will be used in the
slot. The test cases have been changed accordingly to illustrate.

With this patch in place, if a user attempts to assign multiple
functions in a slot without setting the multifunction bit for function
0, libvirt will issue an error when the domain is defined, and the
define operation will fail. In the future, we may decide to detect
this situation and automatically add multifunction=on to avoid the
error; even then it will still be useful to have a manual method of
turning on multifunction since, as stated above, there are some
devices that excpect it to be turned on for all functions in a slot.

A side effect of this patch is that attempts to use the same PCI
address for two different devices will now log an error (previously
this would cause the domain define operation to fail, but there would
be no log message generated). Because the function doing this log was
almost completely rewritten, I didn't think it worthwhile to make a
separate patch for that fix (the entire patch would immediately be
obsoleted).

This patch was made in response to:

  https://bugzilla.redhat.com/show_bug.cgi?id=738095

In short, qemu's default for the rombar setting (which makes the
firmware ROM of a PCI device visible/not on the guest) was previously
0 (not visible), but they recently changed the default to 1
(visible). Unfortunately, there are some PCI devices that fail in the
guest when rombar is 1, so the setting must be exposed in libvirt to
prevent a regression in behavior (it will still require explicitly
setting <rom bar='off'/> in the guest XML).

rombar is forced on/off by adding:

  <rom bar='on|off'/>

inside a <hostdev> element that defines a PCI device. It is currently
ignored for all other types of devices.

At the moment there is no clean method to determine whether or not the
rombar option is supported by QEMU - this patch uses the advice of a
QEMU developer to assume support for qemu-0.12+. There is currently a
patch in the works to put this information in the output of "qemu-kvm
-device pci-assign,?", but of course if we switch to keying off that,
we would lose support for setting rombar on all the versions of qemu
between 0.12 and whatever version gets that patch.

QEMU 0.13 introduced cache=unsafe for -drive, this patch exposes
it in the libvirt layer.

  * Introduced a new QEMU capability flag ($prefix_CACHE_UNSAFE),
    as even if $prefix_CACHE_V2 is set, we can't know if unsafe
    is supported.

  * Improved the reliability of qemu cache type detection.

It is important to be able to attach USB redirected devices to a
particular controller (one that supports USB2 for instance).
Without this patch, only the default bus was used.

     <redirdev bus='usb' type='spicevmc'>
       <address type='usb' bus='0' port='4'/>
     </redirdev>

I got confused when 'virsh domblkinfo dom disk' required the
path to a disk (which can be ambiguous, since a single file
can back multiple disks), rather than the unambiguous target
device name that I was using in disk snapshots.  So, in true
developer fashion, I went for the best of both worlds - all
interfaces that operate on a disk (aka block) now accept
either the target name or the unambiguous path to the backing
file used by the disk.

* src/conf/domain_conf.h (virDomainDiskIndexByName): Add
parameter.
(virDomainDiskPathByName): New prototype.
* src/libvirt_private.syms (domain_conf.h): Export it.
* src/conf/domain_conf.c (virDomainDiskIndexByName): Also allow
searching by path, and decide whether ambiguity is okay.
(virDomainDiskPathByName): New function.
(virDomainDiskRemoveByName, virDomainSnapshotAlignDisks): Update
callers.
* src/qemu/qemu_driver.c (qemudDomainBlockPeek)
(qemuDomainAttachDeviceConfig, qemuDomainUpdateDeviceConfig)
(qemuDomainGetBlockInfo, qemuDiskPathToAlias): Likewise.
* src/qemu/qemu_process.c (qemuProcessFindDomainDiskByPath):
Likewise.
* src/libxl/libxl_driver.c (libxlDomainAttachDeviceDiskLive)
(libxlDomainDetachDeviceDiskLive, libxlDomainAttachDeviceConfig)
(libxlDomainUpdateDeviceConfig): Likewise.
* src/uml/uml_driver.c (umlDomainBlockPeek): Likewise.
* src/xen/xend_internal.c (xenDaemonDomainBlockPeek): Likewise.
* docs/formatsnapshot.html.in: Update documentation.
* tools/virsh.pod (domblkstat, domblkinfo): Likewise.
* docs/schemas/domaincommon.rng (diskTarget): Tighten pattern on
disk targets.
* docs/schemas/domainsnapshot.rng (disksnapshot): Update to match.
* tests/domainsnapshotxml2xmlin/disk_snapshot.xml: Update test.

As discussed here:
https://www.redhat.com/archives/libvir-list/2011-August/msg00361.html
https://www.redhat.com/archives/libvir-list/2011-August/msg00552.html

Adds snapshot attribute and transient sub-element:

<devices>
  <disk type=... snapshot='no|internal|external'>
    ...
    <transient/>
  </disk>
</devices>

* docs/schemas/domaincommon.rng (snapshot): New define.
(disk): Add snapshot and persistent attributes.
* docs/formatdomain.html.in: Document them.
* src/conf/domain_conf.h (virDomainDiskSnapshot): New enum.
(_virDomainDiskDef): New fields.
* tests/qemuxml2argvdata/qemuxml2argv-disk-transient.xml: New
test of rng, no args counterpart until qemu support is complete.
* tests/qemuxml2argvdata/qemuxml2argv-disk-snapshot.args: New
file, snapshot attribute does not affect args.
* tests/qemuxml2argvdata/qemuxml2argv-disk-snapshot.xml: Likewise.
* tests/qemuxml2argvtest.c (mymain): Run new test.

This patch will probably cause merge conflicts to those trying
to do backports.  The end goal is simple - domaincommon.rng
should be the state of domain.rng pre-patch, with a few lines
tweaked in the header, while domain.rng post-patch is now just
a shell that includes domaincommon.rng and sets the <start>.

* docs/schemas/domain.rng: Move guts...
* docs/schemas/domaincommon.rng: ...to new file.
* docs/schemas/domainsnapshot.rng: Allow new xml.
* docs/schemas/Makefile.am (schema_DATA): Distribute new file.
* tests/domainsnapshotxml2xmlout/full_domain.xml: New test.
* libvirt.spec.in (%files client): Ship new file.  Sort lines.
* mingw32-libvirt.spec.in: Likewise.

- create a new "redirdev" element for this purpose

So that devices can be attached to hubs. Example, to attach to first
port of a usb-hub on port 1.

      <hub type='usb'>
         <address type='usb' bus='0' port='1'/>
      </hub>

      <input type='mouse' type='usb'>
         <address type='usb' bus='0' port='1.1'/>
      </hub>

also add a test entry

domain parsing and serialization code, qemu driver backend and
a couple of test

Companion controllers take an extra 'master' attribute to associate
them.

Also add tests for this

Expand the domain and the QEmu driver code
Adds a couple of tests

The model by default is piix3-uchi.

Example:
<controller type='usb' index='0' model='ich9-ehci'/>

List is: piix3-uhci piix4-uhci ehci ich9-ehci1 ich9-uhci1 ich9-uhci2
ich9-uhci3 vt82c686b-uhci pci-ohci

Newer QEMU introduced cache=directsync for -drive, this patchset
is to expose it in libvirt layer.

  * Introduced a new QEMU capability flag ($prefix_CACHE_DIRECTSYNC),
    As even $prefix_CACHE_V2 is set, we can't known if directsync
    is supported.

In some versions of qemu, both virtio-blk-pci and virtio-net-pci
devices can have an event_idx setting that determines some details of
event processing. When it is enabled, it "reduces the number of
interrupts and exits for the guest". qemu will automatically enable
this feature when it is available, but there may be cases where this
new feature could actually make performance worse (NB: no such case
has been found so far).

As a safety switch in case such a situation is encountered in the
field, this patch adds a new attribute "event_idx" to the <driver>
element of both disk and interface devices. event_idx can be set to
"on" (to force event_idx on in case qemu has it disabled by default)
or "off" (for force event_idx off). In the case that event_idx support
isn't present in qemu, the attribute is ignored (this on the advice of
the qemu developer).

docs/formatdomain.html.in: document the new flag (marking it as
   "don't mess with this!"
docs/schemas/domain.rng: add event_idx in appropriate places
src/conf/domain_conf.[ch]: add event_idx to parser and formatter
src/libvirt_private.syms: export
   virDomainVirtioEventIdx(From|To)String
src/qemu/qemu_capabilities.[ch]: detect and report event_idx in
   disk/net
src/qemu/qemu_command.c: add event_idx parameter to qemu commandline
    when appropriate.
tests/qemuxml2argvdata/qemuxml2argv-event_idx.args,
tests/qemuxml2argvdata/qemuxml2argv-event_idx.xml,
tests/qemuxml2argvtest.c,
tests/qemuxml2xmltest.c: test cases for event_idx.

Once it's plugged in, the <listen> element will be an optional
replacement for the "listen" attribute that graphics elements already
have. If the <listen> element is type='address', it will have an
attribute called 'address' which will contain an IP address or dns
name that the guest's display server should listen on. If, however,
type='network', the <listen> element should have an attribute called
'network' that will be set to the name of a network configuration to
get the IP address from.

* docs/schemas/domain.rng: updated to allow the <listen> element

* docs/formatdomain.html.in: document the <listen> element and its
  attributes.

* src/conf/domain_conf.[hc]:

  1) The domain parser, formatter, and data structure are modified to
     support 0 or more <listen> subelements to each <graphics>
     element. The old style "legacy" listen attribute is also still
     accepted, and will be stored internally just as if it were a
     separate <listen> element. On output (i.e. format), the address
     attribute of the first <listen> element of type 'address' will be
     duplicated in the legacy "listen" attribute of the <graphic>
     element.

  2) The "listenAddr" attribute has been removed from the unions in
     virDomainGRaphicsDef for graphics types vnc, rdp, and spice.
     This attribute is now in the <listen> subelement (aka
     virDomainGraphicsListenDef)

  3) Helper functions were written to provide simple access
     (both Get and Set) to the listen elements and their attributes.

* src/libvirt_private.syms: export the listen helper functions

* src/qemu/qemu_command.c, src/qemu/qemu_hotplug.c,
  src/qemu/qemu_migration.c, src/vbox/vbox_tmpl.c,
  src/vmx/vmx.c, src/xenxs/xen_sxpr.c, src/xenxs/xen_xm.c

  Modify all these files to use the listen helper functions rather
  than directly referencing the (now missing) listenAddr
  attribute. There can be multiple <listen> elements to a single
  <graphics>, but the drivers all currently only support one, so all
  replacements of direct access with a helper function indicate index
  "0".

* tests/* - only 3 of these are new files added explicitly to test the
  new <listen> element. All the others have been modified to reflect
  the fact that any legacy "listen" attributes passed in to the domain
  parse will be saved in a <listen> element (i.e. one of the
  virDomainGraphicsListenDefs), and during the domain format function,
  both the <listen> element as well as the legacy attributes will be
  output.

Define new 'bandwidth' element with possible child element 'inbound'
and 'outbound' addressing incoming and outgoing traffic respectively:

<bandwidth>
  <inbound average='1000' peak='2000' burst='5120'/>
  <outbound average='500'/>
</bandwidth>

Leaving any element out means not to shape traffic in that
direction.
The units for average and peak (rate) are in kilobytes per second,
for burst (size) are just in kilobytes.
This element can be inserted into domain's 'interface' and
'network'.

the domain XML <interface> element is updated in the following ways:

1) <virtualportprofile> can be specified when source type='network'
(previously it was only valid for source type='direct')

2) A new attribute "portgroup" has been added to the <source>
element. When source type='network' (the only time portgroup is
recognized), extra configuration information will be taken from the
<portgroup> element of the given name in the network definition.

3) Each virDomainNetDef now also potentially has a
virDomainActualNetDef which is a private object (never
exported/imported via the public API, and not defined in the RNG) that
is used to maintain information about the physical device that was
actually used for a NetDef of type VIR_DOMAIN_NET_TYPE_NETWORK.

The virDomainActualNetDef will only be parsed/formatted if the
parse/format function is called with the
VIR_DOMAIN_XML_INTERNAL_ACTUAL_NET flag set (which is only needed when
saving/loading a running domain's state info to the stateDir).

virtPortProfiles are currently only used in the domain XML, but will
soon also be used in the network XML. To prepare for that change, this
patch moves the structure definition into util/network.h and the parse
and format functions into util/network.c (I decided that this was a
better choice than macvtap.h/c for something that needed to always be
available on all platforms).

Define the element cputune's child elements 'period' and 'quota':
<cputune>
  <period>100000</period>
  <quota>50000</quota>
</cputune>

Kernel cmdline args can be passed to xen pv domains even when a
bootloader is specified.  The current config-to-sxpr mapping
ignores cmdline when bootloader is present.

Since the xend sub-driver is used with many xen toolstack versions,
this patch takes conservative approach of adding an else block to
existing !def->os.bootloader, and only appends sxpr if def->os.cmdline
is non-NULL.

V2: Fix existing testcase broken by this patch and add new testcases