This is from a bug report and conversation on IRC where Soren reported that while a filter update is occurring on one or more VMs (due to a rule having been edited for example), a deadlock can occur when a VM referencing a filter is started.
The problem is caused by the two locking sequences of
qemu driver, qemu domain, filter # for the VM start operation
filter, qemu_driver, qemu_domain # for the filter update operation
that obviously don't lock in the same order. The problem is the 2nd lock sequence. Here the qemu_driver lock is being grabbed in qemu_driver:qemudVMFilterRebuild()
The following solution is based on the idea of trying to re-arrange the 2nd sequence of locks as follows:
qemu_driver, filter, qemu_driver, qemu_domain
and making the qemu driver recursively lockable so that a second lock can occur, this would then lead to the following net-locking sequence
qemu_driver, filter, qemu_domain
where the 2nd qemu_driver lock has been ( logically ) eliminated.
The 2nd part of the idea is that the sequence of locks (filter, qemu_domain) and (qemu_domain, filter) becomes interchangeable if all code paths where filter AND qemu_domain are locked have a preceding qemu_domain lock that basically blocks their concurrent execution
So, the following code paths exist towards qemu_driver:qemudVMFilterRebuild where we now want to put a qemu_driver lock in front of the filter lock.
-> nwfilterUndefine() [ locks the filter ]
-> virNWFilterTestUnassignDef()
-> virNWFilterTriggerVMFilterRebuild()
-> qemudVMFilterRebuild()
-> nwfilterDefine()
-> virNWFilterPoolAssignDef() [ locks the filter ]
-> virNWFilterTriggerVMFilterRebuild()
-> qemudVMFilterRebuild()
-> nwfilterDriverReload()
-> virNWFilterPoolLoadAllConfigs()
->virNWFilterPoolObjLoad()
-> virNWFilterPoolAssignDef() [ locks the filter ]
-> virNWFilterTriggerVMFilterRebuild()
-> qemudVMFilterRebuild()
-> nwfilterDriverStartup()
-> virNWFilterPoolLoadAllConfigs()
->virNWFilterPoolObjLoad()
-> virNWFilterPoolAssignDef() [ locks the filter ]
-> virNWFilterTriggerVMFilterRebuild()
-> qemudVMFilterRebuild()
Qemu is not the only driver using the nwfilter driver, but also the UML driver calls into it. Therefore qemuVMFilterRebuild() can be exchanged with umlVMFilterRebuild() along with the driver lock of qemu_driver that can now be a uml_driver. Further, since UML and Qemu domains can be running on the same machine, the triggering of a rebuild of the filter can touch both types of drivers and their domains.
In the patch below I am now extending each nwfilter callback driver with functions for locking and unlocking the (VM) driver (UML, QEMU) and introduce new functions for locking all registered callback drivers and unlocking them. Then I am distributing the lock-all-cbdrivers/unlock-all-cbdrivers call into the above call paths. The last shown callpath starting with nwfilterDriverStart() is problematic since it is initialize before the Qemu and UML drives are and thus a lock in the path would result in a NULL pointer attempted to be locked -- the call to virNWFilterTriggerVMFilterRebuild() is never called, so we never lock either the qemu_driver or the uml_driver in that path. Therefore, only the first 3 paths now receive calls to lock and unlock all callback drivers. Now that the locks are distributed where it matters I can remove the qemu_driver and uml_driver lock from qemudVMFilterRebuild() and umlVMFilterRebuild() and not requiring the recursive locks.
For now I want to put this out as an RFC patch. I have tested it by 'stretching' the critical section after the define/undefine functions each lock the filter so I can (easily) concurrently execute another VM operation (suspend,start). That code is in this patch and if you want you can de-activate it. It seems to work ok and operations are being blocked while the update is being done.
I still also want to verify the other assumption above that locking filter and qemu_domain always has a preceding qemu_driver lock.
Adding parsing code for memory tunables in the domain xml file
also change the internal define structures used for domain memory
informations
Adds a new specific test
Public api to set/get memory tunables supported by the hypervisors.
dv:
* some cleanups in libvirt.c
* adding extra checks in libvirt.c new entry points
v4:
* Move exporting public API to this patch
* Add unsigned int flags to the public api for future extensions
v3:
* Add domainGetMemoryParamters and NULL in all the driver interface
v2:
* Initialize domainSetMemoryParameters to NULL in all the driver
interface structure.
When nwfilter support was added to UML, I didn't realise the UML driver
needed instrumentation to make updating nwfilters on the fly work. This
patch adds this bit of glue.
Signed-off-by: Soren Hansen <soren@linux2go.dk>
For privileged UML connections (uml:///system), we shouldn't use root's
home dir, but rather somewhere in /var/run/libvirt/uml-guest.
https://bugzilla.redhat.com/show_bug.cgi?id=499536
Signed-off-by: Soren Hansen <soren@linux2go.dk>
UML supports hot plugging and unplugging of various devices. This patch
exposes this functionality for disks.
Signed-off-by: Soren Hansen <soren@linux2go.dk>
Like the comment suggested, we just open the file and pass the file
descriptor to uml. The input "stream" is set to "null", since I couldn't
find any useful way to actually use a file for input for a chardev and
this also mimics what e.g. QEmu does internally.
Signed-off-by: Soren Hansen <soren@linux2go.dk>
* src/uml/uml_driver.c (umlMonitorCommand): Validate that enough
bytes were read to dereference both res.length, and that many
bytes from res.data.
Reported by Soren Hansen.
Add the library entry point for the new virDomainQemuMonitorCommand()
entry point. Because this is not part of the "normal" libvirt API,
it gets its own header file, library file, and will eventually
get its own over-the-wire protocol later in the series.
Changes since v1:
- Go back to using the virDriver table for qemuDomainMonitorCommand, due to
linking issues
- Added versioning information to the libvirt-qemu.so
Changes since v2:
- None
Changes since v3:
- Add LGPL header to libvirt-qemu.c
- Make virLibConnError and virLibDomainError macros instead of function calls
Changes since v4:
- Move exported symbols to libvirt_qemu.syms
Signed-off-by: Chris Lalancette <clalance@redhat.com>
* src/uml/uml_driver.c (umlMonitorCommand): Correct flaw that would
cause unconditional "incomplete reply ..." failure, since "nbytes"
was always 0 or 1.
Otherwise, a malicious packet could cause a DoS via spurious
out-of-memory failure.
* src/uml/uml_driver.c (umlMonitorCommand): Validate that incoming
data is reliable before using it to allocate/dereference memory.
Don't report bogus errno on short read.
Reported by Jim Meyering.
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/'
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
virDomainManagedSave() is to be run on a running domain. Once the call
complete, as in virDomainSave() the domain is stopped upon completion,
but there is no restore counterpart as any order to start the domain
from the API would load the state from the managed file, similary if
the domain is autostarted when libvirtd starts.
Once a domain has restarted his managed save image is destroyed,
basically managed save image can only exist for a stopped domain,
for a running domain that would be by definition outdated data.
* include/libvirt/libvirt.h.in src/libvirt.c src/libvirt_public.syms:
adds the new entry points virDomainManagedSave(),
virDomainHasManagedSaveImage() and virDomainManagedSaveRemove()
* src/driver.h 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/qemu/qemu_driver.c src/vbox/vbox_tmpl.c
src/remote/remote_driver.c src/test/test_driver.c src/uml/uml_driver.c
src/xen/xen_driver.c: add corresponding new internal drivers entry
points
virParseVersionString uses virStrToLong_ui instead of sscanf.
This also fixes a bug in the UML driver, that always returned 0
as version number.
Introduce STRSKIP to check if a string has a certain prefix and
to skip this prefix.
When a domain is defined on host1, migrated to host2 and then migrated
back to host1, its current configuration would overwrite the libvirtd's
in-memory copy of persistent configuration of that domain. This is not
desired as we want to preserve the persistent configuration untouched.
This patch introduces new 'live' parameter to virDomainAssignDef.
Passing 'true' for 'live' means the configuration passed to
virDomainAssignDef describes a configuration of live instance of the
domain. This applies for saved domains which are being restored or for
incoming domains during migration.
All callers have been changed to pass the appropriate value.
The current virDomainAttachDevice API can be (ab)used to change
the media of an existing CDROM/Floppy device. Going forward there
will be more devices that can be configured on the fly and overloading
virDomainAttachDevice for this is not too pleasant. This patch adds
a new virDomainUpdateDeviceFlags() explicitly just for modifying
existing devices.
* include/libvirt/libvirt.h.in: Add virDomainUpdateDeviceFlags
* src/driver.h: Internal API for virDomainUpdateDeviceFlags
* src/libvirt.c, src/libvirt_public.syms: Glue public API to
driver API
* 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/qemu/qemu_driver.c,
src/remote/remote_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: Add
stubs for new driver entry point
The current API for domain events has a number of problems
- Only allows for domain lifecycle change events
- Does not allow the same callback to be registered multiple times
- Does not allow filtering of events to a specific domain
This introduces a new more general purpose domain events API
typedef enum {
VIR_DOMAIN_EVENT_ID_LIFECYCLE = 0, /* virConnectDomainEventCallback */
...more events later..
}
int virConnectDomainEventRegisterAny(virConnectPtr conn,
virDomainPtr dom, /* Optional, to filter */
int eventID,
virConnectDomainEventGenericCallback cb,
void *opaque,
virFreeCallback freecb);
int virConnectDomainEventDeregisterAny(virConnectPtr conn,
int callbackID);
Since different event types can received different data in the callback,
the API is defined with a generic callback. Specific events will each
have a custom signature for their callback. Thus when registering an
event it is neccessary to cast the callback to the generic signature
eg
int myDomainEventCallback(virConnectPtr conn,
virDomainPtr dom,
int event,
int detail,
void *opaque)
{
...
}
virConnectDomainEventRegisterAny(conn, NULL,
VIR_DOMAIN_EVENT_ID_LIFECYCLE,
VIR_DOMAIN_EVENT_CALLBACK(myDomainEventCallback)
NULL, NULL);
The VIR_DOMAIN_EVENT_CALLBACK() macro simply does a "bad" cast
to the generic signature
* include/libvirt/libvirt.h.in: Define new APIs for registering
domain events
* src/driver.h: Internal driver entry points for new events APIs
* src/libvirt.c: Wire up public API to driver API for events APIs
* src/libvirt_public.syms: Export new APIs
* 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/qemu/qemu_driver.c, src/remote/remote_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 new API entries
This provides the internal glue for the driver API
* src/driver.h: Internal API contract
* src/libvirt.c, src/libvirt_public.syms: Connect public API
to driver API
* 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/qemu/qemu_driver.c, src/remote/remote_driver.c,
src/test/test_driver.c src/uml/uml_driver.c, src/vbox/vbox_tmpl.c,
src/xen/xen_driver.c: Stub out entry points
The internal glue layer for the new pubic API
* src/driver.h: Define internal driver API contract
* src/libvirt.c, src/libvirt_public.syms: Wire up public
API to internal driver API
* 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/qemu/qemu_driver.c, src/remote/remote_driver.c,
src/test/test_driver.c, src/uml/uml_driver.c, src/vbox/vbox_tmpl.c,
src/xen/xen_driver.c: Stub new entry point
* src/uml/uml_driver.c (umlMonitorCommand): This function would
sometimes return -1, yet fail to free the "reply" it had allocated.
Hence, no caller would know to free the corresponding argument.
When returning -1, be sure to free all allocated resources.
* src/lxc/lxc_container.c src/lxc/lxc_controller.c src/lxc/lxc_driver.c
src/network/bridge_driver.c src/qemu/qemu_driver.c
src/uml/uml_driver.c: virFileMakePath returns 0 for success, or the
value of errno on failure, so error checking should be to test
if non-zero, not if lower than 0
Set up the types for the domainMemoryStats function and insert it into the
virDriver structure definition. Because of static initializers, update
every driver and set the new field to NULL.
* include/libvirt/libvirt.h.in: new API
* src/driver.h src/*/*_driver.c src/vbox/vbox_tmpl.c: add the new
entry to the driver structure
* python/generator.py: fix compiler errors, the actual python binding is
implemented later
* src/driver.h: add an extra entry point in the structure
* 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/qemu/qemu_driver.c
src/remote/remote_driver.c src/test/test_driver.c src/uml/uml_driver.c
src/vbox/vbox_tmpl.c src/xen/xen_driver.c: add NULL entry points for
all drivers
There is currently no way to determine the libvirt version of a remote
libvirtd we are connected to. This is a useful piece of data to enable
feature detection.
Introduce a number of new APIs to expose some boolean properties
of objects, which cannot otherwise reliably determined, nor are
aspects of the XML configuration.
* virDomainIsActive: Checking virDomainGetID is not reliable
since it is not possible to distinguish between error condition
and inactive domain for ID of -1.
* virDomainIsPersistent: Check whether a persistent config exists
for the domain
* virNetworkIsActive: Check whether the network is active
* virNetworkIsPersistent: Check whether a persistent config exists
for the network
* virStoragePoolIsActive: Check whether the storage pool is active
* virStoragePoolIsPersistent: Check whether a persistent config exists
for the storage pool
* virInterfaceIsActive: Check whether the host interface is active
* virConnectIsSecure: whether the communication channel to the
hypervisor is secure
* virConnectIsEncrypted: whether any network based commnunication
channels are encrypted
NB, a channel can be secure, even if not encrypted, eg if it does
not involve the network, like a UNIX socket, or pipe.
* include/libvirt/libvirt.h.in: Define public API
* src/driver.h: Define internal driver API
* src/libvirt.c: Implement public API entry point
* src/libvirt_public.syms: Export API symbols
* src/esx/esx_driver.c, src/lxc/lxc_driver.c,
src/interface/netcf_driver.c, src/network/bridge_driver.c,
src/opennebula/one_driver.c, src/openvz/openvz_driver.c,
src/phyp/phyp_driver.c, src/qemu/qemu_driver.c,
src/remote/remote_driver.c, src/test/test_driver.c,
src/uml/uml_driver.c, src/vbox/vbox_tmpl.c,
src/xen/xen_driver.c: Stub out driver tables
