The qemu driver contains a subtle race in the logic to find next
available vnc port. Currently it iterates through all available ports
and returns the first for which bind(2) succeeds. However it is possible
that a previously issued port has not yet been bound by qemu, resulting
in the same port used for a subsequent domain.
This patch addresses the race by using a simple bitmap to "reserve" the
ports allocated by libvirt.
V2:
- Put port bitmap in struct qemud_driver
- Initialize bitmap in qemudStartup
V3:
- Check for failure of virBitmapGetBit
- Additional check for port != -1 before calling virbitmapClearBit
V4:
- Check for failure of virBitmap{Set,Clear}Bit
We need a common internal function for starting managed domains to be
used during autostart. This patch factors out relevant code from
qemudDomainStart into qemudDomainObjStart and makes it use the
refactored code for domain restore instead of calling qemudDomainRestore
API directly.
We need to be able to restore a domain which we already locked and
started a job for it without undoing these steps. This patch factors
out internals of qemudDomainRestore into separate functions which work
for locked objects.
* src/qemu/qemu_conf.c (qemudParseHelpStr): Fix errors that made
it impossible to diagnose invalid minor and micro version number
components.
Signed-off-by: Chris Wright <chrisw@redhat.com>
The current cleanup: in StartVMDaemon path is a poor duplication.
qemuShutdownVMDaemon can handle teardown for inactive VMs, so let's use it.
v2: Remove old abort: label, only use cleanup:
* src/qemu/qemu_conf.c (QEMU_VERSION_STR_1, QEMU_VERSION_STR_2):
Define these instead of...
(QEMU_VERSION_STR): ... this. Remove definition.
(qemudParseHelpStr): Check first for the new, shorter prefix,
"QEMU emulator version", and then for the old one,
"QEMU PC emulator version" when trying to parse the version number.
Based on a patch by Chris Wright.
There doesn't seem to be anything specific to tap devices for this
array of file descriptors which need to stay open of the guest to use.
Rename then for others to make use of.
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Chris Lalancette <clalance@redhat.com>
Do not require each caller of virStorageFileGetMetadata and
virStorageFileGetMetadataFromFD to first clear the storage of the
"meta" buffer. Instead, initialize that storage in
virStorageFileGetMetadataFromFD.
* src/util/storage_file.c (virStorageFileGetMetadataFromFD): Clear
"meta" here, not before each of the following callers.
* src/qemu/qemu_driver.c (qemuSetupDiskCgroup): Don't clear "meta" here.
(qemuTeardownDiskCgroup): Likewise.
* src/qemu/qemu_security_dac.c (qemuSecurityDACSetSecurityImageLabel):
Likewise.
* src/security/security_selinux.c (SELinuxSetSecurityImageLabel):
Likewise.
* src/security/virt-aa-helper.c (get_files): Likewise.
Approximately 60 messages were marked. Since these diagnostics are
intended solely for developers and maintainers, encouraging translation
is deemed to be counterproductive:
http://thread.gmane.org/gmane.comp.emulators.libvirt/25050/focus=25052
Run this command:
git grep -l VIR_WARN|xargs perl -pi -e \
's/(VIR_WARN0?)\s*\(_\((".*?")\)/$1($2/'
There were three very similar uses of qemuMonitorAddDrive.
This change makes the three 17-line sequences identical.
* src/qemu/qemu_driver.c (qemudDomainAttachPciDiskDevice): Detect
failure. Add VIR_WARN and braces.
(qemudDomainAttachSCSIDisk): Add VIR_WARN and braces.
(qemudDomainAttachUsbMassstorageDevice): Likewise.
History has shown that there are frequent bugs in the QEMU driver
code leading to the monitor being invoked with a NULL pointer.
Although the QEMU driver code should always report an error in
this case before invoking the monitor, as a safety net put in a
generic check in the monitor code entry points.
* src/qemu/qemu_monitor.c: Safety net to check for NULL monitor
object
Any method which intends to invoke a monitor command must have
a check for virDomainObjIsActive() before using the monitor to
ensure that priv->mon != NULL.
There is one subtle edge case in this though. If a method invokes
multiple monitor commands, and calls qemuDomainObjExitMonitor()
in between two of these commands then there is no guarentee that
priv->mon != NULL anymore. This is because the QEMU process may
exit or die at any time, and because qemuDomainObjEnterMonitor()
releases the lock on virDomainObj, it is possible for the background
thread to close the monitor handle and thus qemuDomainObjExitMonitor
will release the last reference allowing priv->mon to become NULL.
This affects several methods, most notably migration but also some
hotplug methods. This patch takes a variety of approaches to solve
the problem, depending on the particular usage scenario. Generally
though it suffices to add an extra virDomainObjIsActive() check
if qemuDomainObjExitMonitor() was called during the method.
* src/qemu/qemu_driver.c: Fix multiple potential NULL pointer flaws
in usage of the monitor
* src/qemu/qemu_driver.c (qemudDomainSetVcpus): Upon look-up failure,
i.e., vm==NULL, goto cleanup, rather than to "endjob", superficially
since the latter would dereference vm, but more fundamentally because
we certainly don't want to call qemuDomainObjEndJob before we've
even attempted qemuDomainObjBeginJob.
(gdb) p/x QEMUD_CMD_FLAG_VNET_HOST
$7 = 0xffffffff80000000
Oops - that meant we were incorrectly setting QEMU_CMD_FLAG_RTC_TD_HACK
for qemu-kvm-0.12.3 (and probably botching a few other settings as well).
Fixes Red Hat BZ#592070
* src/qemu/qemu_conf.h (QEMUD_CMD_FLAG_VNET_HOST): Avoid sign
extension.
* tests/qemuhelpdata/qemu-kvm-0.12.3: New file.
* tests/qemuhelptest.c (mymain): Add another case.
A fedora translator filed:
https://bugzilla.redhat.com/show_bug.cgi?id=580816
Pointing out these two error messages as unclear: "write save" sounds
like a typo without context, and lack of a colon made the second message
difficult to parse.
virFileResolveLink was returning a positive value on error,
thus confusing callers that assumed failure was < 0. The
confusion is further evidenced by callers that would have
ended up calling virReportSystemError with a negative value
instead of a valid errno.
Fixes Red Hat BZ #591363.
* src/util/util.c (virFileResolveLink): Live up to documentation.
* src/qemu/qemu_security_dac.c
(qemuSecurityDACRestoreSecurityFileLabel): Adjust callers.
* src/security/security_selinux.c
(SELinuxRestoreSecurityFileLabel): Likewise.
* src/storage/storage_backend_disk.c
(virStorageBackendDiskDeleteVol): Likewise.
qemuReadLogOutput early VM death detection is racy and won't always work.
Startup then errors when connecting to the VM monitor. This won't report
the emulator cmdline output which is typically the most useful diagnostic.
Check if the VM has died at the very end of the monitor connection step,
and if so, report the cmdline output.
See also: https://bugzilla.redhat.com/show_bug.cgi?id=581381
* src/qemu/qemu_driver.c (qemudDomainSetVcpus): Avoid NULL-deref
upon unknown UUID. Call qemuDomainObjBeginJob(vm) only after
ensuring that vm != NULL, not before. This potential NULL-deref
was introduced by commit 2c555d87b0.
The code specifies driver->cacheDir as the format string,
but it usually doesn't contain '%s', so the subsequent
argument, "/qemu.mem.XXXXXX", is always ignored.
The patch fixes the misuse.
Setting dynamic_ownership=0 in /etc/libvirt/qemu.conf prevents
libvirt's DAC security driver from setting uid/gid on disk
files when starting/stopping QEMU, allowing the admin to manage
this manually. As a side effect it also stopped setting of
uid/gid when saving guests to a file, which completely breaks
save when QEMU is running non-root. Thus saved state labelling
code must ignore the dynamic_ownership parameter
* src/qemu/qemu_security_dac.c: Ignore dynamic_ownership=0 when
doing save/restore image labelling
When QEMU runs with its disk on NFS, and as a non-root user, the
disk is chownd to that non-root user. When migration completes
the last step is shutting down the QEMU on the source host. THis
normally resets user/group/security label. This is bad when the
VM was just migrated because the file is still in use on the dest
host. It is thus neccessary to skip the reset step for any files
found to be on a shared filesystem
* src/libvirt_private.syms: Export virStorageFileIsSharedFS
* src/util/storage_file.c, src/util/storage_file.h: Add a new
method virStorageFileIsSharedFS() to determine if a file is
on a shared filesystem (NFS, GFS, OCFS2, etc)
* src/qemu/qemu_driver.c: Tell security driver not to reset
disk labels on migration completion
* src/qemu/qemu_security_dac.c, src/qemu/qemu_security_stacked.c,
src/security/security_selinux.c, src/security/security_driver.h,
src/security/security_apparmor.c: Add ability to skip disk
restore step for files on shared filesystems.
The cgroups ACL code was only allowing the primary disk image.
It is possible to chain images together, so we need to search
for backing stores and add them to the ACL too. Since the ACL
only handles block devices, we ignore the EINVAL we get from
plain files. In addition it was missing code to teardown the
cgroup when hot-unplugging a disk
* src/qemu/qemu_driver.c: Allow backing stores in cgroup ACLs
and add missing teardown code in unplug path
QEMU is gaining a new monitor command netdev_add for hotplugging
NICs using the netdev backend code. We already support this on
the command this, though it is disabled. This adds support for
hotplug too, also to remain disabled until 0.13 QEMU is released
* src/qemu/qemu_driver.c: Support netdev hotplug for NICs
* src/qemu/qemu_monitor.c, src/qemu/qemu_monitor.h,
src/qemu/qemu_monitor_json.c, src/qemu/qemu_monitor_json.h,
src/qemu/qemu_monitor_text.c, src/qemu/qemu_monitor_text.h: Add
support for netdev_add and netdev_remove commands
When closing a monitor using qemuMonitorClose(), we are aware of
the possibility the monitor is still being used somewhere:
/* NB: ordinarily one might immediately set mon->watch to -1
* and mon->fd to -1, but there may be a callback active
* that is still relying on these fields being valid. So
* we merely close them, but not clear their values and
* use this explicit 'closed' flag to track this state */
but since we call virEventAddHandle() on that monitor without increasing
its ref counter, the monitor is still freed which makes possible users
of it quite unhappy. The unhappiness can lead to a hang if qemuMonitorIO
tries to lock mutex which no longer exists.
With the introduction of the generic qemu device model, unplugging
SCSI disks works like a charm, so support it in libvirt.
* src/qemu/qemu_driver.c: Add qemudDomainDetachSCSIDiskDevice() to do the
unplugging, extend qemudDomainDetachDeviceAdd().
Signed-off-by: Wolfgang Mauerer <wolfgang.mauerer@siemens.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
Support for live migration between hosts that do not share storage was
added to qemu-kvm release 0.12.1.
It supports two flags:
-b migration without shared storage with full disk copy
-i migration without shared storage with incremental copy (same base image
shared between source and destination).
I tested the live migration without shared storage (both flags) for native
and p2p with and without tunnelling. I also verified that the fix doesn't
affect normal migration with shared storage.
WIN32 is always defined when __MINGW32__ is defined, but the
converse is not true. WIN32 is more generic, if someone were
to ever attempt porting to a microsoft compiler. This does
not affect Cygwin, which intentionally does not define WIN32.
* src/qemu/qemu_driver.c (qemuDomainGetBlockInfo): Use more
generic flag macro.
* src/storage/storage_backend.c
(virStorageBackendUpdateVolTargetInfoFD)
(virStorageBackendRunProgRegex): Likewise.
* tools/console.h (vshRunConsole): Likewise.
This introduces a new event type
VIR_DOMAIN_EVENT_ID_IO_ERROR_REASON
This event is the same as the previous VIR_DOMAIN_ID_IO_ERROR
event, but also includes a string describing the cause of
the event.
Thus there is a new callback definition for this event type
typedef void (*virConnectDomainEventIOErrorReasonCallback)(virConnectPtr conn,
virDomainPtr dom,
const char *srcPath,
const char *devAlias,
int action,
const char *reason,
void *opaque);
This is currently wired up to the QEMU block IO error events
* daemon/remote.c: Dispatch IO error events to client
* examples/domain-events/events-c/event-test.c: Watch for
IO error events
* include/libvirt/libvirt.h.in: Define new IO error event ID
and callback signature
* src/conf/domain_event.c, src/conf/domain_event.h,
src/libvirt_private.syms: Extend API to handle IO error events
* src/qemu/qemu_driver.c: Connect to the QEMU monitor event
for block IO errors and emit a libvirt IO error event
* src/remote/remote_driver.c: Receive and dispatch IO error
events to application
* src/remote/remote_protocol.x: Wire protocol definition for
IO error events
* src/qemu/qemu_monitor.c, src/qemu/qemu_monitor.h,
src/qemu/qemu_monitor_json.c: Watch for BLOCK_IO_ERROR event
from QEMU monitor
When using -device syntax, the IO event will have a different
prefix, 'drive-' that needs to be skipped over before matching
against the libvirt disk alias
* src/qemu/qemu_driver.c: Skip QEMU_DRIVE_HOST_PREFIX in IO event
This defines the internal driver API and stubs out each driver
* src/driver.h: Define virDrvDomainGetBlockInfo signature
* src/libvirt.c, src/libvirt_public.syms: Glue public API to drivers
* src/esx/esx_driver.c, src/lxc/lxc_driver.c, src/opennebula/one_driver.c,
src/openvz/openvz_driver.c, src/phyp/phyp_driver.c,
src/test/test_driver.c, src/uml/uml_driver.c, src/vbox/vbox_tmpl.c,
src/xen/xen_driver.c, src/xenapi/xenapi_driver.c: Stub out driver
qemuDomainPCIAddressSetFree was freeing up the hash
table for the pci addresses, but not freeing up the addr
structure. Looking over the callers of this function, it
seems like they expect it to also free up the structure,
so do that here.
Signed-off-by: Chris Lalancette <clalance@redhat.com>
The previous commit changes a goto from 'endjob' to 'cleanup',
leaving the endjob label unused. Remove it to avoid compile
warning.
* src/qemu/qemu_driver.c: Remove 'endjob' label
* src/qemu/qemu_driver.c (qemuDomainSnapshotCreateXML): When setting
"vm" to NULL, jump over vm-dereferencing code to "cleanup".
(qemuDomainRevertToSnapshot): Likewise.
In cases where the security driver failed to restore a label after a
guest has saved, we mistakenly jumped to the error cleanup paths.
This is not good, because the operation has in fact completed and
cannot be rolled back completely. Label restore is non-critical, so
just log the problem instead. Also add a missing restore call in
the error cleanup path
* src/qemu/qemu_driver.c: Fix handling of security driver
restore failures in QEMU domain save
When cgroups is enabled, access to block devices is likely to be
restricted to a whitelist. Prior to saving a guest to a block device,
it is necessary to add the block device to the whitelist. This is
not required upon restore, since QEMU reads from stdin
* src/qemu/qemu_driver.c: Add block device to cgroups whitelist
if neccessary during domain save.
The save process was relying on use of the shell >> append
operator to ensure the save data was placed after the libvirt
header + XML. This doesn't work for block devices though.
Replace this code with use of 'dd' and its 'seek' parameter.
This means that we need to pad the header + XML out to a
multiple of dd block size (in this case we choose 512).
The qemuMonitorMigateToCommand() monitor API is used for both
save/coredump, and migration via UNIX socket. We can't simply
switch this to use 'dd' since this causes problems with the
migration usage. Thus, create a dedicated qemuMonitorMigateToFile
which can accept an filename + offset, and remove the filename
from the current qemuMonitorMigateToCommand() API
* src/qemu/qemu_driver.c: Switch to qemuMonitorMigateToFile
for save and core dump
* src/qemu/qemu_monitor.c, src/qemu/qemu_monitor.h,
src/qemu/qemu_monitor_json.c, src/qemu/qemu_monitor_json.h,
src/qemu/qemu_monitor_text.c, src/qemu/qemu_monitor_text.h: Create
a new qemuMonitorMigateToFile, separate from the existing
qemuMonitorMigateToCommand to allow handling file offsets
It is possible to use block devices with domain save/restore. Upon
failure QEMU unlinks the path being saved to. This isn't good when
it is a block device !
* src/qemu/qemu_driver.c: Don't unlink block devices if save fails
If a transient QEMU crashes during save attempt, then the virDomainPtr
object may be freed. If a persistent QEMU crashes during save, then
the 'priv->mon' field is no longer valid since it will be inactive.
* src/qemu/qemu_driver.c: Fix two crashes when QEMU exits
during a save attempt
In particular I was forgetting to take the qemuMonitorPrivatePtr
lock (via qemuDomainObjBeginJob), which would cause problems
if two users tried to access the same domain at the same time.
This patch also fixes a problem where I was forgetting to remove
a transient domain from the list of domains.
Thanks to Stephen Shaw for pointing out the problem and testing
out the initial patch.
Signed-off-by: Chris Lalancette <clalance@redhat.com>
With JSON qemu monitor, we get a STOP event from qemu whenever qemu
stops guests CPUs. The downside of it is that vm->state is changed to
PAUSED and a new generic paused event is send to applications. However,
when we ask qemu to stop the CPUs we are not really interested in qemu
event and we usually want to issue a more specific event.
By setting vm->status to PAUSED before actually sending the request to
qemu (and resetting it back if the request fails) we can ignore the
event since the event handler does nothing when the guest is already
paused. This solution is quite hacky but unfortunately it's the best
solution which I was able to come up with and it doesn't introduce a
race condition.
While doing some testing of the snapshot code I noticed that
if qemuDomainSnapshotLoad failed, it would print a NULL as
part of the error. That's not desirable, so leave the
full_path variable around until after we are done printing
errors.
Signed-off-by: Chris Lalancette <clalance@redhat.com>
It's not needed and is currently ignored, but this is a bug.
It will get fixed soon and QMP will return an error for keys
it doesn't know about, this will break libvirt.
* src/qemu/qemu_monitor_json.c: remove qemuMonitorJSONCommandAddTimestamp()
and the place where it's invoked in qemuMonitorJSONMakeCommand()
* The error messages coming from qemu's DAC support contain strings
from the original SELinux security driver code. This just removes
references to "security context" and other SELinux-isms from the DAC
code.
Signed-off-by: Spencer Shimko <sshimko@tresys.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
The hang fix in d376b7d63e was incomplete
since it left quite a few {Enter,Exit}Monitor calls which require driver
to be unlocked. Since the driver is locked throughout the whole
function, {Enter,Exit}MonitorWithDriver need to be used instead to
ensure driver is not locked when issuing monitor commands.
The comment in qemuDomainWaitForMigrationComplete says we are polling
every 50ms but the code sleeps only for 50us. This was already discussed
during review but apparently forgotten when the series was pushed.
The text monitor code was checking for a '\n' prefix on several
places. Previously this would work, but since the monitor code
re-write the '\n' is already stripped off, so mustn't be checked
for.
* src/qemu/qemu_monitor_text.c: Fix monitor error checking
Probably as a result of a merge error, the CPU hotplug command
names were completely wrong.
* src/qemu/qemu_monitor_json.c, src/qemu/qemu_monitor_text.c: Fix
the CPU hotplug command names
Adds ability to provide a preferred CPU model for CPUID data decoding.
Such model would be considered as the best possible model (if it's
supported by hypervisor) regardless on number of features which have to
be added or removed for describing required CPU.
So far, when CPUID data were converted into CPU model and features, the
features can only be added to the model. As a result, when a guest asked
for something like "qemu64,-svm" it would get a qemu32 plus a bunch of
additional features instead.
This patch adds support for removing feature from the base model.
Selection algorithm remains the same: the best CPU model is the model
which requires lowest number of features to be added/removed from it.
Qemu committed a patch which list some CPU names in [] when asked for
supported CPUs (qemu -cpu ?). Yet, it needs such CPUs to be passed
without those square braces. When probing for supported CPU models, we
can just strip the square braces and pretend we have never seen them.
First, inital VCPU pinning is set correctly but then it is reset by
assigning qemu process to a new cgroup (which contains all CPUs). It's
easily fixed by swapping these two actions.
The initial boot of VMs uses -device for NICs where available. The
corresponding monitor command is device_add, but the network hotplug
code was still using device_del by mistake.
* src/qemu/qemu_driver.c: Use device_add for NIC hotplug where
available
If either of the getfd or host_net_add monitor commands return
any text, this indicates an error condition. Don't ignore this!
* src/qemu/qemu_monitor_text.c: Report errors for getfd and
host_net_add
The 'device_del' command expects a parameter called 'id' but we
were passing 'config'.
* src/qemu/qemu_monitor_json.c: Fix device_del command parameter
Disk devices in QEMU have two parts, the guest device and the host
backend driver. Historically these two parts have had the same
"unique" name. With the switch to using -device though, they now
have separate names. Thus when changing CDROM media, for guests
using -device syntax, we need to prepend the QEMU_DRIVE_HOST_PREFIX
constant
* src/qemu/qemu_conf.c, src/qemu/qemu_conf.h: Add helper function
qemuDeviceDriveHostAlias() for building a host backend alias
* src/qemu/qemu_driver.c: Use qemuDeviceDriveHostAlias() to determine
the host backend alias for performing eject/change commands in the
monitor
The device_add command was added in JSON mode in a way I didn't
expect. Instead of passing the normal device string to the JSON
command:
{ "execute": "device_add", "arguments": { "device": "ne2k_pci,id=nic.1,netdev=net.1" } }
We need to split up the device string into a full JSON object
{ "execute": "device_add", "arguments": { "driver": "ne2k_pci", "id": "nic.1", "netdev": "net.1" } }
* src/qemu/qemu_conf.h, src/qemu/qemu_conf.c: Rename the
qemuCommandLineParseKeywords method to qemuParseKeywords
and export it to monitor
* src/qemu/qemu_monitor_json.c: Split up device string into
a JSON object for device_add command
The parameter for the qemuMonitorDeviceDel() is a device alias,
not a device config string. Rename the parameter reflect this
and avoid confusion to readers.
* src/qemu/qemu_monitor.c, src/qemu/qemu_monitor.h,
src/qemu/qemu_monitor_json.c, src/qemu/qemu_monitor_json.h,
src/qemu/qemu_monitor_text.c, src/qemu/qemu_monitor_text.h:
Rename devicestr to devalias in qemuMonitorDeviceDel()
The QEMU developers have stated that they will not be porting
the commands 'pci_add', 'pci_del', 'usb_add', 'usb_del' to the
JSON mode monitor, since they're obsoleted by 'device_add'
and 'device_del'. libvirt has (untested) code that would have
supported those commands in theory, but since we already use
device_add/del where available, there's no need to keep the
legacy stuff anymore.
The text mode monitor keeps support for all commands for sake
of historical compatability.
* src/qemu/qemu_monitor_json.c: Remove 'pci_add', 'pci_del',
'usb_add', 'usb_del' commands
The QEMU driver is mistakenly calling directly into the text
mode monitor for the domain memory stats query.
* src/qemu/qemu_driver.c: Replace qemuMonitorTextGetMemoryStats with
qemuMonitorGetMemoryStats
* src/qemu/qemu_monitor.c, src/qemu/qemu_monitor.h: Add the new
wrapper for qemuMonitorGetMemoryStats
* src/qemu/qemu_monitor_json.c, src/qemu/qemu_monitor_json.h: Add
qemuMonitorJSONGetMemoryStats implementation
Instead of reporting VIR_ERR_INTERNAL_ERROR use the more specific
VIR_ERR_CONFIG_UNSUPPORTED
* src/qemu/qemu_conf.c: Report VIR_ERR_CONFIG_UNSUPPORTED for
unsupported video adapters
To avoid race-conditions, the tear down of a filter has to happen before
the tap interface disappears and another tap interface with the same
name can re-appear. This patch tries to fix this. In one place, where
communication with the qemu monitor may fail, I am only tearing the
filters down after knowing that the function did not fail.
I am also moving the tear down functions into an include file for other
drivers to reuse.
* src/qemu/qemu_driver.c (qemudDomainAttachSCSIDisk):
Initialize "cont" to NULL, so clang knows it's set.
Add an sa_assert so it knows it's non-NULL when dereferenced.
In a couple of cases typos meant we were firing the wrong type
of event. In the python code my previous commit accidentally
missed some chunks of the code.
* python/libvirt-override-virConnect.py: Add missing python glue
accidentally left out of previous commit
* src/conf/domain_event.c, src/qemu/qemu_monitor_json.c: Fix typos
in event name / method name to invoke
Currently when we attempt to change the cdrom in a qemu VM the monitor
doesn't generate an error if the target filename doesn't exist. I've
submitted a patch[1] for this. This patch is the libvirt qemu-driver
side which catches the error message from the monitor and reportes the
error to libvirt. This means that virsh attach-disk cdrom commands
won't appear to succeed when qemu change command actually failed.
* src/qemu/qemu_monitor_text.c: in qemuMonitorTextChangeMedia() look
for failure to access the new data
When qemu libvirt driver doesn't support guest CPU selection with given
qemu binary, guests requiring specific CPU should fail to start instead
of being silently supplied with a default CPU.
