There are several reasons for doing this:

- the CPU specification is out of libvirt's control so we cannot
  guarantee stable guest ABI
- not every feature of a CPU may actually work as expected when
  advertised directly to a guest
- migration between two machines with exactly the same CPU may work but
  no guarantees can be made
- this mode is not supported and its use is at one's own risk

There are three address validation routines that do nothing:
  virDomainDeviceDriveAddressIsValid()
  virDomainDeviceUSBAddressIsValid()
  virDomainDeviceVirtioSerialAddressIsValid()

Remove them, and replace their call sites with "1" which is what they
currently return. In some cases this means we can remove an entire
if block.
Signed-off-by: NMichael Ellerman <michael@ellerman.id.au>

Adding a new model for virtio-scsi roughly follows the same scheme
as the previous patch.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

KVM will be able to use a PCI SCSI controller even on POWER.  Let
the user specify the vSCSI controller by other means than a default.

After this patch, the QEMU driver will actually look at the model
and reject anything but auto, lsilogic and ibmvscsi.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

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.

This fixes https://bugzilla.redhat.com/show_bug.cgi?id=638633

Although scripts are not used by interfaces of type other than
"ethernet" in qemu, due to the fact that the parser stores the script
name in a union that is only valid when type is ethernet or bridge,
there is no way for anyone except the parser itself to catch the
problem of specifying an interface script for an inappropriate
interface type (by the time the parsed data gets back to the code that
called the parser, all evidence that a script was specified is
forgotten).

Since the parser itself should be agnostic to which type of interface
allows scripts (an example of why: a script specified for an interface
of type bridge is valid for xen domains, but not for qemu domains),
the solution here is to move the script out of the union(s) in the
DomainNetDef, always populate it when specified (regardless of
interface type), and let the driver decide whether or not it is
appropriate.

Currently the qemu, xen, libxml, and uml drivers recognize the script
parameter and do something with it (the uml driver only to report that
it isn't supported). Those drivers have been updated to log a
CONFIG_UNSUPPORTED error when a script is specified for an interface
type that's inappropriate for that particular hypervisor.

(NB: There was earlier discussion of solving this problem by adding a
VALIDATE flag to all libvirt APIs that accept XML, which would cause
the XML to be validated against the RNG files. One statement during
that discussion was that the RNG shouldn't contain hypervisor-specific
things, though, and a proper solution to this problem would require
that (again, because a script for an interface of type "bridge" is
accepted by xen, but not by qemu).

Implement the parsing and formatting of the XML addition of
the previous commit.  The new XML doesn't affect qemu command
line, so we can now test round-trip XML->memory->XML handling.

I chose to reuse the existing structure, even though per-device
override doesn't use all of those fields, rather than create a
new structure, in order to reuse more code.

* src/conf/domain_conf.h (_virDomainDiskDef): Add seclabel member.
* src/conf/domain_conf.c (virDomainDiskDefFree): Free it.
(virSecurityLabelDefFree): New function.
(virDomainDiskDefFormat): Print it.
(virSecurityLabelDefFormat): Reduce output if model not present.
(virDomainDiskDefParseXML): Alter signature, and parse seclabel.
(virSecurityLabelDefParseXML): Split...
(virSecurityLabelDefParseXMLHelper): ...into new helper.
(virDomainDeviceDefParse, virDomainDefParseXML): Update callers.
* tests/qemuxml2argvdata/qemuxml2argv-seclabel-dynamic-override.args:
New file.
* tests/qemuxml2xmltest.c (mymain): Enhance test.
* tests/qemuxml2argvtest.c (mymain): Likewise.

Pure code motion; no semantic change.

* src/conf/domain_conf.h (virDomainSeclabelType)
(virSecurityLabelDefPtr): Declare earlier.
* src/conf/domain_conf.c (virSecurityLabelDefClear)
(virSecurityLabelDefParseXML): Move earlier.
(virDomainDefParseXML): Move seclabel parsing earlier.

Add a util function virDomainNetFind to find a domain's net def.

For QEMU PPC64 we have a machine type ("pseries") which has a virtual
bus called "spapr-vio". We need to be able to create devices on this
bus, and as such need a way to specify the address for those devices.

This patch adds a new address type "spapr-vio", which achieves this.

The addressing is specified with a "reg" property in the address
definition. The reg is optional, if it is not specified QEMU will
auto-assign an address for the device.
Signed-off-by: NMichael Ellerman <michael@ellerman.id.au>

Set up the types for the numa functions and insert them into the
virDriver structure definition.

This chunk of code below repeated in several functions, factor it into
a helper method virDomainLiveConfigHelperMethod to eliminate duplicated code
based on Eric and Adam's suggestion. I have tested it for all the
relevant APIs changed.
Signed-off-by: NEric Blake <eblake@redhat.com>
Signed-off-by: NLei Li <lilei@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>

None of the callers cared if str was updated to point to the next
byte after the parsed cpuset; simplifying this results in quite
a few code simplifications.  Additionally, virCPUDefParseXML was
strdup()'ing a malloc()'d string; avoiding a memory copy resulted
in less code.

* src/conf/domain_conf.h (virDomainCpuSetParse): Alter signature.
* src/conf/domain_conf.c (virDomainCpuSetParse): Don't modify str.
(virDomainVcpuPinDefParseXML, virDomainDefParseXML): Adjust
callers.
* src/conf/cpu_conf.c (virCPUDefParseXML): Likewise.
* src/xen/xend_internal.c (sexpr_to_xend_topology): Likewise.
* src/xen/xm_internal.c (xenXMDomainPinVcpu): Likewise.
* src/xenxs/xen_sxpr.c (xenParseSxpr): Likewise.
* src/xenxs/xen_xm.c (xenParseXM): Likewise.

Now, when we support multiple consoles per domain,
the vm->def->console[0] can still remain an alias
for vm->def->serial[0]; However, we need to copy
it's source definition as well otherwise we'll regress
on virDomainOpenConsole.

The virDomainNetGetActualBridgeName and virDomainNetGetActualDirectDev
methods both return strings that point to data in the virDomainDefPtr
struct, and should therefore not be freed. The return values should
thus be 'const char *' not 'char *'.

* src/conf/domain_conf.c, src/conf/domain_conf.h: Mark const
* src/network/bridge_driver.c: Update to use a const char *

Rename the macvtap.c file to virnetdevmacvlan.c to reflect its
functionality. Move the port profile association code out into
virnetdevvportprofile.c. Make the APIs available unconditionally
to callers

* src/util/macvtap.h: rename to src/util/virnetdevmacvlan.h,
* src/util/macvtap.c: rename to src/util/virnetdevmacvlan.c
* src/util/virnetdevvportprofile.c, src/util/virnetdevvportprofile.h:
  Pull in vport association code
* src/Makefile.am, src/conf/domain_conf.h, src/qemu/qemu_conf.c,
  src/qemu/qemu_conf.h, src/qemu/qemu_driver.c: Update include
  paths & remove conditional compilation

The src/util/network.c file is a dumping ground for many different
APIs. Split it up into 5 pieces, along functional lines

 - src/util/virnetdevbandwidth.c: virNetDevBandwidth type & helper APIs
 - src/util/virnetdevvportprofile.c: virNetDevVPortProfile type & helper APIs
 - src/util/virsocketaddr.c: virSocketAddr and APIs
 - src/conf/netdev_bandwidth_conf.c: XML parsing / formatting
   for virNetDevBandwidth
 - src/conf/netdev_vport_profile_conf.c: XML parsing / formatting
   for virNetDevVPortProfile

* src/util/network.c, src/util/network.h: Split into 5 pieces
* src/conf/netdev_bandwidth_conf.c, src/conf/netdev_bandwidth_conf.h,
  src/conf/netdev_vport_profile_conf.c, src/conf/netdev_vport_profile_conf.h,
  src/util/virnetdevbandwidth.c, src/util/virnetdevbandwidth.h,
  src/util/virnetdevvportprofile.c, src/util/virnetdevvportprofile.h,
  src/util/virsocketaddr.c, src/util/virsocketaddr.h: New pieces
* daemon/libvirtd.h, daemon/remote.c, src/conf/domain_conf.c,
  src/conf/domain_conf.h, src/conf/network_conf.c,
  src/conf/network_conf.h, src/conf/nwfilter_conf.h,
  src/esx/esx_util.h, src/network/bridge_driver.c,
  src/qemu/qemu_conf.c, src/rpc/virnetsocket.c,
  src/rpc/virnetsocket.h, src/util/dnsmasq.h, src/util/interface.h,
  src/util/iptables.h, src/util/macvtap.c, src/util/macvtap.h,
  src/util/virnetdev.h, src/util/virnetdevtap.c,
  tools/virsh.c: Update include files

Rename the virVirtualPortProfileParams struct to be
virNetDevVPortProfile, and rename the APIs to match
this prefix.

* src/util/network.c, src/util/network.h: Rename port profile
  APIs
* src/conf/domain_conf.c, src/conf/domain_conf.h,
  src/conf/network_conf.c, src/conf/network_conf.h,
  src/network/bridge_driver.c, src/qemu/qemu_hotplug.c,
  src/util/macvtap.c, src/util/macvtap.h: Update for
  renamed APIs/structs

Rename virBandwidth to virNetDevBandwidth, and virRate to
virNetDevBandwidthRate.

* src/util/network.c, src/util/network.h: Rename bandwidth
  structs and APIs
* src/conf/domain_conf.c, src/conf/domain_conf.h,
  src/conf/network_conf.c, src/conf/network_conf.h,
  src/lxc/lxc_driver.c, src/network/bridge_driver.c,
  src/qemu/qemu_command.c, src/util/macvtap.c,
  src/util/macvtap.h, tools/virsh.c: Update for API changes.

The default console type may vary based on the OS type. ie a Xen
paravirt guests wants a 'xen' console, while a fullvirt guests
wants a 'serial' console.

A plain integer default console type in the capabilities does
not suffice. Instead introduce a callback that is passed the
OS type.

* src/conf/capabilities.h: Use a callback for default console
  type
* src/conf/domain_conf.c, src/conf/domain_conf.h: Use callback
  for default console type. Add missing LXC/OpenVZ console types.
* src/esx/esx_driver.c, src/libxl/libxl_conf.c,
  src/lxc/lxc_conf.c, src/openvz/openvz_conf.c,
  src/phyp/phyp_driver.c, src/qemu/qemu_capabilities.c,
  src/uml/uml_conf.c, src/vbox/vbox_tmpl.c,
  src/vmware/vmware_conf.c, src/xen/xen_hypervisor.c,
  src/xenapi/xenapi_driver.c: Set default console type callback

While Xen only has a single paravirt console, UML, and
QEMU both support multiple paravirt consoles. The LXC
driver can also be trivially made to support multiple
consoles. This patch extends the XML to allow multiple
<console> elements in the XML. It also makes the UML
and QEMU drivers support this config.

* src/conf/domain_conf.c, src/conf/domain_conf.h: Allow
  multiple <console> devices
* src/lxc/lxc_driver.c, src/xen/xen_driver.c,
  src/xenxs/xen_sxpr.c, src/xenxs/xen_xm.c: Update for
  internal API changes
* src/security/security_selinux.c, src/security/virt-aa-helper.c:
  Only label consoles that aren't a copy of the serial device
* src/qemu/qemu_command.c, src/qemu/qemu_driver.c,
  src/qemu/qemu_process.c, src/uml/uml_conf.c,
  src/uml/uml_driver.c: Support multiple console devices
* tests/qemuxml2xmltest.c, tests/qemuxml2argvtest.c: Extra
  tests for multiple virtio consoles. Set QEMU_CAPS_CHARDEV
  for all console /channel tests
* tests/qemuxml2argvdata/qemuxml2argv-channel-virtio-auto.args,
  tests/qemuxml2argvdata/qemuxml2argv-channel-virtio.args
  tests/qemuxml2argvdata/qemuxml2argv-console-virtio.args: Update
  for correct chardev syntax
* tests/qemuxml2argvdata/qemuxml2argv-console-virtio-many.args,
  tests/qemuxml2argvdata/qemuxml2argv-console-virtio-many.xml: New
  test file

To support "managed" mode of host PCI device, we record the original
states (unbind_from_stub, remove_slot, and reprobe) so that could
reattach the device to host with original driver. But there is no XML
for theses attrs, and thus after daemon is restarted, we lose the
original states. It's easy to reproduce:

    1) virsh start domain
    2) virsh attach-device dom hostpci.xml (in 'managed' mode)
    3) service libvirtd restart
    4) virsh destroy domain

    You will see the device won't be bound to the original driver
if there was one.

This patch is to solve the problem by introducing internal XML
(won't be dumped to user, only dumped to status XML). The XML is:
    <origstates>
      <unbind/>
      <remove_slot/>
      <reprobe/>
    </origstates>

Which will be child node of <hostdev><source>...</souce></hostdev>.
(only for PCI device).

A new struct "virDomainHostdevOrigStates" is introduced for the XML,
and the according members are updated when preparing the PCI device.
And function "qemuUpdateActivePciHostdevs" is modified to honor
the original states. Use of qemuGetPciHostDeviceList is removed
in function "qemuUpdateActivePciHostdevs", and the "managed" value of
the device config is honored by the change. This fixes another problem
alongside:

    qemuGetPciHostDeviceList set the device as "managed" force
    regardless of whether the device is configured as "managed='yes'"
    or not in XML, which is not right.

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.

Add a test for the simple parts of my indentation changes, and
fix the fallout.

* tests/domainsnapshotxml2xmltest.c: New test.
* tests/Makefile.am (domainsnapshotxml2xmltest_SOURCES): Build it.
* src/conf/domain_conf.c (virDomainSnapshotDefFormat): Avoid NULL
deref, match documented order.
* src/conf/domain_conf.h (virDomainSnapshotDefFormat): Add const.
* tests/domainsnapshotxml2xmlout/all_parameters.xml: Tweak output.
* tests/domainsnapshotxml2xmlout/disk_snapshot.xml: Likewise.
* tests/domainsnapshotxml2xmlout/full_domain.xml: Likewise.
* .gitignore: Exempt new binary.

<domainsnapshot> is the first public instance of <domain> being
used as a sub-element, although we have two other private uses
(runtime state, and migration cookie).  Although indentation has
no effect on XML parsing, using it makes the output more consistent.

This uses virBuffer auto-indentation to obtain the effect, for all
but the portions of <domain> that are not generated a line at a
time into the same virBuffer.  Further patches will clean up the
remaining problems.

* src/conf/domain_conf.h (virDomainDefFormatInternal): New prototype.
* src/conf/domain_conf.c (virDomainDefFormatInternal): Export.
(virDomainObjFormat, virDomainSnapshotDefFormat): Update callers.
* src/libvirt_private.syms (domain_conf.h): Add new export.
* src/qemu/qemu_migration.c (qemuMigrationCookieXMLFormat): Use
new function.
(qemuMigrationCookieXMLFormatStr): Update caller.

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>

The previous optimizations lead to some follow-on cleanups.

* src/conf/domain_conf.c (virDomainSnapshotForEachChild)
(virDomainSnapshotForEachDescendant): Drop dead parameter.
(virDomainSnapshotActOnDescendant)
(virDomainSnapshotObjListNumFrom)
(virDomainSnapshotObjListGetNamesFrom): Update callers.
* src/qemu/qemu_driver.c (qemuDomainSnapshotNumChildren)
(qemuDomainSnapshotListChildrenNames, qemuDomainSnapshotDelete):
Likewise.
* src/conf/domain_conf.h: Update prototypes.

No one was using virDomainSnapshotHasChildren, but that was an
O(n) function.  Exposing and tracking a bit more metadata for each
snapshot will allow the same query to be made with an O(1) query
of the member field.  For single snapshot operations (create,
delete), callers can be trusted to maintain the metadata themselves,
but for reloading, we can't compute parents as we go since there
is no guarantee that parents were parsed before children, so we also
provide a function to refresh the relationships, and which can
be used to detect if the user has ignored our warnings and been
directly modifying files in /var/lib/libvirt/qemu/snapshot.  This
patch only adds metadata; later patches will actually use it.

This layout intentionally hardcodes the size of each snapshot struct,
by tracking sibling pointers, rather than having to deal with the
headache of yet more memory management by directly sticking a
dynamically sized child[] on each parent.

* src/conf/domain_conf.h (_virDomainSnapshotObj)
(_virDomainSnapshotObjList): Add members.
(virDomainSnapshotUpdateRelations, virDomainSnapshotDropParent):
New prototypes.
(virDomainSnapshotHasChildren): Delete.
* src/conf/domain_conf.c (virDomainSnapshotSetRelations)
(virDomainSnapshotUpdateRelations, virDomainSnapshotDropParent):
New functions.
(virDomainSnapshotHasChildren): Drop unused function.
* src/libvirt_private.syms (domain_conf): Update exports.

Not too hard to wire up.  The trickiest part is realizing that
listing children of a snapshot cannot use SNAPSHOT_LIST_ROOTS,
and that we overloaded that bit to also mean SNAPSHOT_LIST_DESCENDANTS;
we use that bit to decide which iteration to use, but don't want
the existing counting/listing functions to see that bit.

* src/conf/domain_conf.h (virDomainSnapshotObjListNumFrom)
(virDomainSnapshotObjListGetNamesFrom): New prototypes.
* src/conf/domain_conf.c (virDomainSnapshotObjListNumFrom)
(virDomainSnapshotObjListGetNamesFrom): New functions.
* src/libvirt_private.syms (domain_conf.h): Export them.
* src/qemu/qemu_driver.c (qemuDomainSnapshotNumChildren)
(qemuDomainSnapshotListChildrenNames): New functions.

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).

While adding a new enum, I noticed a VIR_ENUM_DECL for a type that
doesn't exist. There is also of course no matching VIR_ENUM_IMPL for
it.

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.

A new element is introduced to XML that allows to control
state of virtual network interfaces in hypervisors.

Live modification of the link state allows networking tools
propagate topology changes to guest OS or testing of
scenarios in complex (virtual) networks.

This patch adds elements to XML grammars and parsing and generating
code.