May 2018 - Devel - libvirt List Archives

Re: [libvirt] [PATCH 0/3] sample: vfio mdev display devices.
by Alex Williamson 08 Aug '18

08 Aug '18

On Mon, 9 Apr 2018 12:35:10 +0200 Gerd Hoffmann <kraxel(a)redhat.com> wrote: > This little series adds three drivers, for demo-ing and testing vfio > display interface code. There is one mdev device for each interface > type (mdpy.ko for region and mbochs.ko for dmabuf). Erik Skultety brought up a good question today regarding how libvirt is meant to handle these different flavors of display interfaces and knowing whether a given mdev device has display support at all. It seems that we cannot simply use the default display=auto because libvirt needs to specifically configure gl support for a dmabuf type interface versus not having such a requirement for a region interface, perhaps even removing the emulated graphics in some cases (though I don't think we have boot graphics through either solution yet). Additionally, GVT-g seems to need the x-igd-opregion support enabled(?), which is a non-starter for libvirt as it's an experimental option! Currently the only way to determine display support is through the VFIO_DEVICE_QUERY_GFX_PLANE ioctl, but for libvirt to probe that on their own they'd need to get to the point where they could open the vfio device and perform the ioctl. That means opening a vfio container, adding the group, setting the iommu type, and getting the device. I was initially a bit appalled at asking libvirt to do that, but the alternative is to put this information in sysfs, but doing that we risk that we need to describe every nuance of the mdev device through sysfs and it becomes a dumping ground for every possible feature an mdev device might have. So I was ready to return and suggest that maybe libvirt should probe the device to know about these ancillary configuration details, but then I remembered that both mdev vGPU vendors had external dependencies to even allow probing the device. KVMGT will fail to open the device if it's not associated with an instance of KVM and NVIDIA vGPU, I believe, will fail if the vGPU manager process cannot find the QEMU instance to extract the VM UUID. (Both of these were bad ideas) Therefore, how can libvirt know if a given mdev device supports a display and which type of display it supports, and potentially which vendor specific options might be required to further enable that display (if they weren't experimental)? A terrible solution would be that libvirt hard codes that NVIDIA works with regions and Intel works with dmabufs, but even then there's a backwards and forwards compatibility problem, that libvirt needs to support older kernels and drivers where display support is not present and newer drivers where perhaps Intel is now doing regions and NVIDIA is supporting dmabuf, so it cannot simply be assumed based on the vendor. The only solution I see down that path would be identifying specific {vendor,type} pairs that support a predefined display type, but that's just absurd to think that vendors would rev their mdev types to expose this and that libvirt would keep a database mapping types to features. We also have the name and description attributes, but these are currently free form, so libvirt rightfully ignores them entirely. I don't know if we could create a defined feature string within those free form strings. Otherwise, it seems we have no choice but to dive into the pool of exposing such features via sysfs and we'll need to be vigilant of feature creep or vendor specific features (ex. we're not adding a feature to indicate an opregion requirement). How should we do this? Perhaps a bar we can set is that if a feature cannot be discovered through a standard vfio API, then it is not suitable for this sysfs API. Such things can be described via our existing mdev vendor specific attribute interface. We currently have this sysfs interface: mdev_supported_types/ |-- $VENDOR_TYPE | |-- available_instances | |-- create | |-- description | |-- device_api | |-- devices | `-- name ioctls for vfio devices which only provide information include: VFIO_DEVICE_GET_INFO VFIO_DEVICE_GET_REGION_INFO VFIO_DEVICE_GET_IRQ_INFO VFIO_DEVICE_GET_PCI_HOT_RESET_INFO VFIO_DEVICE_QUERY_GFX_PLANE We don't need to support all of these initially, but here's a starting idea for what this may look like in sysfs: $VENDOR_TYPE/ |-- available_instances |-- create |-- description |-- device_api |-- devices |-- name `-- vfio-pci `-- device |-- gfx_plane | |-- dmabuf | `-- region |-- irqs | |-- 0 | | |-- count | | `-- flags | `-- 1 | |-- count | `-- flags `-- regions |-- 0 | |-- flags | |-- offset | `-- size `-- 3 |-- flags |-- offset `-- size The existing device_api file reports "vfio-pci", so we base the device API info in a directory named vfio-pci. We're specifically exposing device information, so we have a device directory. We have a GFX_PLANE query ioctl, so we have a gfx_plane sub-directory. I imagine the dmabuf and region files here expose either Y/N or 1/0. I continue on the example with how we might expose irqs and regions, but even with regions we can bury down into how is sparse mmap exposed, how are device specific regions described, etc. Filling this in to completion without a specific userspace need to expose the information is just an exercise in bloating the kernel. That almost begins to look reasonable, but then we can only expose this for mdev devices, what if we were to hack a back door into a directly assigned GPU that tracks the location of active display in the framebuffer and implement the GFX_PLANE interface for that? We have no sysfs representation for either the template or the actual device for anything other than mdev. This inconsistency with physically assigned devices has been one of my arguments against enhancing mdev sysfs. Thanks to anyone still reading this. Ideas how we might help libvirt fill this information void so that they can actually configure a VM with a display device? Thanks, Alex

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[libvirt] [PATCH libvirt v2 0/9] Fix virConnectRegisterCloseCallback and get rid of global variables
by Marc Hartmayer 07 Aug '18

07 Aug '18

The first part of this patch series fixes the behavior of virConnectRegisterCloseCallback and converts the testDriver to virObjectLockable. The subsequent patches remove the need to have the global variables 'qemuProgram' and 'remoteProgram' in libvirtd.[ch]. They only work in combination with the fixed behavior of virConnectRegisterCloseCallback. Changelog: + v1->v2: - Removed accepted patches - Removed NACKed patches - Added r-b to patch 5 - Worked in comments - Rebased - Added patches 7-9 Marc Hartmayer (9): virConnectRegisterCloseCallback: Cleanup 'opaque' if there is no connectRegisterCloseCallback test: Convert testDriver to virObjectLockable remote: Add the information which program has to be used to daemonClientEventCallback remote: Use domainClientEventCallbacks for remoteReplayConnectionClosedEvent rpc: Introduce virNetServerGetProgramLocked helper function remote/rpc: Use virNetServerGetProgram() to determine the program rpc: use the return value of virObjectRef directly remote: remove ATTRIBUTE_UNUSED when attribute is actually used remote: shrink the critical sections src/libvirt-host.c | 10 +- src/libvirt_remote.syms | 1 + src/remote/remote_daemon.c | 4 +- src/remote/remote_daemon.h | 3 - src/remote/remote_daemon_dispatch.c | 264 +++++++++++++++++++++++------------- src/rpc/gendispatch.pl | 6 + src/rpc/virnetserver.c | 57 ++++++-- src/rpc/virnetserver.h | 2 + src/test/test_driver.c | 200 ++++++++++++--------------- 9 files changed, 328 insertions(+), 219 deletions(-) -- 2.13.4

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[libvirt] [PATCH v3 0/2] Support network stats for VF representor interface
by Jai Singh Rana 25 Jul '18

25 Jul '18

With availability of switchdev model in linux, it is possible to capture stats for SR-IOV device with interface_type as 'hostdev' provided device supports VF represontor in switchdev mode[1] on host. These stats are supported by adding helper APIs for getting/verifying VF representor name based on PCI Bus:Device:Function information in domains 'hostdev' structure and querying required net sysfs directory and file entries on host according to switchdev model. These helper APIs are then used in qemu/conf to get the interface stats for VF representor on host of pci SR-IOV device. [1] https://www.kernel.org/doc/Documentation/networking/switchdev.txt V2 https://www.redhat.com/archives/libvir-list/2018-February/msg00561.html Jai Singh Rana (2): util: Add helper APIs to get/verify VF Representor name qemu: conf: Network stats support for VF Representors docs/news.xml | 9 ++ po/POTFILES.in | 1 + src/conf/domain_conf.c | 15 ++ src/libvirt_private.syms | 7 + src/qemu/qemu_driver.c | 33 +++- src/util/Makefile.inc.am | 2 + src/util/virhostdev.c | 2 +- src/util/virhostdev.h | 8 + src/util/virnetdevhostdev.c | 374 ++++++++++++++++++++++++++++++++++++++++++++ src/util/virnetdevhostdev.h | 35 +++++ 10 files changed, 481 insertions(+), 5 deletions(-) create mode 100644 src/util/virnetdevhostdev.c create mode 100644 src/util/virnetdevhostdev.h -- 2.13.6

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[libvirt] [PATCH 0/2] Minor fixes for virTypedParams(De)Serialize
by Marc Hartmayer 07 Jul '18

07 Jul '18

Some minor fixes and two questions: * Is the first method, which is described in the documentation for virTypedParamsDeserialize, in sync with the actual code? ("Older APIs do not rely on deserializer allocating memory for @params, ...") * Do we also have to set *nparams = 0 in case of an error and the user has allocated the memory? (virTypedParamsDeserialize) Marc Hartmayer (2): virTypedParamsSerialize: minor fixes virTypedParamsDeserialize: minor fixes src/util/virtypedparam.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) -- 2.13.4

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[libvirt] [PATCH 0/9] Resolve libvirtd hang on termination with connected long running client
by John Ferlan 06 Jul '18

06 Jul '18

RFC: https://www.redhat.com/archives/libvir-list/2018-January/msg00318.html Adjustments since RFC... Patches 1&2: No change, were already R-B'd Patch 3: Removed code as noted in code review, update commit message Patch 4: From old series removed, see below for more details Patch 9: no change NB: Patches 5-8 and 10 from Nikolay Shirokovskiy <nshirokovskiy(a)virtuozzo.com> are removed as they seemed to not be necessary Replaced the former patch 4 with series of patches to (slowly) provide support to disable new connections, handle removing waiting jobs, causing the waiting workers to quit, and allow any running jobs to complete. As it turns out, waiting for running jobs to complete cannot be done from the virNetServerClose callbacks because that means the event loop processing done during virNetServerRun will not allow any currently long running worker job thread a means to complete. So when virNetDaemonQuit is called as a result of the libvirtd signal handlers for SIG{QUIT|INT|TERM}, instead of just causing virNetServerRun to quit immediately, alter to using a quitRequested flag and then use that quitRequested flag to check for long running worker threads before causing the event loop to quit resulting in libvirtd being able to run through the virNetDaemonClose processing. John Ferlan (9): libvirtd: Alter refcnt processing for domain server objects libvirtd: Alter refcnt processing for server program objects netserver: Remove ServiceToggle during ServerDispose util: Introduce virThreadPoolDrain rpc: Introduce virNetServerQuitRequested rpc: Introduce virNetServerWorkerCount rpc: Alter virNetDaemonQuit processing docs: Add news article for libvirtd issue APPLY ONLY FOR TESTING PURPOSES daemon/libvirtd.c | 43 +++++++++++++++++++++++--------- docs/news.xml | 12 +++++++++ src/libvirt_private.syms | 1 + src/libvirt_remote.syms | 2 ++ src/qemu/qemu_driver.c | 5 ++++ src/rpc/virnetdaemon.c | 45 +++++++++++++++++++++++++++++++++- src/rpc/virnetserver.c | 52 ++++++++++++++++++++++++++++++++++++--- src/rpc/virnetserver.h | 4 +++ src/util/virthreadpool.c | 64 ++++++++++++++++++++++++++++++++++++++++-------- src/util/virthreadpool.h | 2 ++ 10 files changed, 204 insertions(+), 26 deletions(-) -- 2.13.6

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[libvirt] [PATCH] util: return generic error in virCopyLastError if error is not set
by Nikolay Shirokovskiy 02 Jul '18

02 Jul '18

virCopyLastError is intended to be used after last error is set. However due to virLastErrorObject failures (very unlikely through as thread local error is allocated on first use) we can have zero fields in a copy as a result. In particular code field can be set to VIR_ERR_OK. In some places (qemu monitor, qemu agent and qemu migaration code for example) we use copy result as a flag and this leads to bugs. Let's set copy result to generic error ("cause unknown") in this case. Approach is based on John Ferlan comments in [1] and [2] to initial attempt which fixes issue in much less generic way. [1] https://www.redhat.com/archives/libvir-list/2018-April/msg02700.html [2] https://www.redhat.com/archives/libvir-list/2018-May/msg00124.html --- src/util/virerror.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/src/util/virerror.c b/src/util/virerror.c index c000b00..9f158af 100644 --- a/src/util/virerror.c +++ b/src/util/virerror.c @@ -343,7 +343,7 @@ virCopyLastError(virErrorPtr to) if (err) virCopyError(err, to); else - virResetError(to); + virErrorGenericFailure(err); return to->code; } -- 1.8.3.1

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Re: [libvirt] [Qemu-devel] [PATCH v7 1/3] qmp: adding 'wakeup-suspend-support' in query-target
by Markus Armbruster 20 Jun '18

20 Jun '18

Cc'ing a few more people. Daniel Henrique Barboza <danielhb(a)linux.ibm.com> writes: > When issuing the qmp/hmp 'system_wakeup' command, what happens in a > nutshell is: > > - qmp_system_wakeup_request set runstate to RUNNING, sets a wakeup_reason > and notify the event > - in the main_loop, all vcpus are paused, a system reset is issued, all > subscribers of wakeup_notifiers receives a notification, vcpus are then > resumed and the wake up QAPI event is fired > > Note that this procedure alone doesn't ensure that the guest will awake > from SUSPENDED state - the subscribers of the wake up event must take > action to resume the guest, otherwise the guest will simply reboot. > > At this moment there are only two subscribers of the wake up event: one > in hw/acpi/core.c and another one in hw/i386/xen/xen-hvm.c. This means > that system_wakeup does not work as intended with other architectures. > > However, only the presence of 'system_wakeup' is required for QGA to > support 'guest-suspend-ram' and 'guest-suspend-hybrid' at this moment. > This means that the user/management will expect to suspend the guest using > one of those suspend commands and then resume execution using system_wakeup, > regardless of the support offered in system_wakeup in the first place. > > This patch adds a new flag called 'wakeup-suspend-support' in TargetInfo > that allows the caller to query if the guest supports wake up from > suspend via system_wakeup. It goes over the subscribers of the wake up > event and, if it's empty, it assumes that the guest does not support > wake up from suspend (and thus, pm-suspend itself). > > This is the expected output of query-target when running a x86 guest: > > {"execute" : "query-target"} > {"return": {"arch": "x86_64", "wakeup-suspend-support": true}} > > This is the output when running a pseries guest: > > {"execute" : "query-target"} > {"return": {"arch": "ppc64", "wakeup-suspend-support": false}} > > Given that the TargetInfo structure is read-only, adding a new flag to > it is backwards compatible. There is no need to deprecate the old > TargetInfo format. > > With this extra tool, management can avoid situations where a guest > that does not have proper suspend/wake capabilities ends up in > inconsistent state (e.g. > https://github.com/open-power-host-os/qemu/issues/31) > > Reported-by: Balamuruhan S <bala24(a)linux.vnet.ibm.com> > Signed-off-by: Daniel Henrique Barboza <danielhb(a)linux.ibm.com> Is query-target is the right place to carry this flag? v7 is rather late for this kind of question; my sincere apologies. The flag is true after qemu_register_wakeup_notifier(). Callers so far: * piix4_pm_realize() via acpi_pm1_cnt_init() This is the realize method of device PIIX4_PM. It's an optional onboard device (suppressed by -no-acpi) of machine types pc-i440fx-VERSION, pc-VERSION, malta. * pc_q35_init() via ich9_lpc_pm_init(), ich9_pm_init(), acpi_pm1_cnt_init() This is the initialization method of machine types pc-q35-VERSION. Note that -no-acpi is not honored. * vt82c686b_pm_realize() via acpi_pm1_cnt_init() This is the realize method of device VT82C686B_PM. It's an onboard device of machine type fulong2e. Again, -no-acpi is not honored. * xen_hvm_init() This one gets called with -accel xen. I suspect the actual callback xen_wakeup_notifier() doesn't actually make wakeup work, unlike the acpi_notify_wakeup() callback registered by the other callers. Issue#1: this calls into question your assumption that the existence of a wake-up notifier implies wake-up works. It still holds if --accel xen is only accepted together with other configuration that triggers registration of acpi_notify_wakeup(). Is it? Stefano, Anthony? Issue#2: the flag isn't a property of the target. Due to -no-acpi, it's not even a property of the machine type. If it was, query-machines would be the natural owner of the flag. Perhaps query-machines is still the proper owner. The value of wakeup-suspend-support would have to depend on -no-acpi for the machine types that honor it. Not ideal; I'd prefer MachineInfo to be static. Tolerable? I guess that's also a libvirt question.

3 14

[libvirt] Call to virDomainIsActive hangs forever
by Mathieu Tarral 14 Jun '18

14 Jun '18

Hi ! I'm submitting my messages on this mailing list to request a bit of help on a case that I have where a Python application makes a call to virDomainIsActive, and the call never returns. I have tried to investigate, but as there are no debug symbols for libvirt on Debian Stretch, i can only have the following GDB backtrace: (gdb) bt #0 pthread_cond_wait@@GLIBC_2.3.2 () at ../sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185 #1 0x00007f49026f5b76 in virCondWait () from /usr/lib/libvirt.so.0 #2 0x00007f4902808bab in ?? () from /usr/lib/libvirt.so.0 #3 0x00007f490280a433 in virNetClientSendWithReply () from /usr/lib/libvirt.so.0 #4 0x00007f490280abe2 in virNetClientProgramCall () from /usr/lib/libvirt.so.0 #5 0x00007f49027e0ea4 in ?? () from /usr/lib/libvirt.so.0 #6 0x00007f49027ea1bb in ?? () from /usr/lib/libvirt.so.0 #7 0x00007f49027b0ef3 in virDomainIsActive () from /usr/lib/libvirt.so.0 #8 0x00007f4902b7fbd0 in libvirt_virDomainIsActive () from /usr/lib/python3/dist-packages/libvirtmod.cpython-35m-x86_64-linux-gnu.so #9 0x0000558eeec696df in PyCFunction_Call () at ../Objects/methodobject.c:109 The libvirt driver used is QEMU, and i have a specific monitoring in place using virtual machine introspection: https://github.com/KVM-VMI/kvm-vmi Now this specific monitoring somehow triggers this bug, and at this point, i don't know if it's a corner case in the libvirt QEMU driver or not. That's why i would like to have your lights on this. libvirt version: 3.0.0-4 -> Could you tell me where i should look in the code ? -> Do you have more information about this virCondWait ? Which condition is it waiting for ? -> How can i get the symbols without having the recompile libvirt and install it system wide, erasing the binaries installed by the package ? Best regards, -- Mathieu Tarral

5 11

[libvirt] [RFC v3] external (pull) backup API
by Eric Blake 13 Jun '18

13 Jun '18

Here's my updated counterproposal for a backup API. In comparison to v2 posted by Nikolay: https://www.redhat.com/archives/libvir-list/2018-April/msg00115.html - changed terminology a bit: Nikolay's "BlockSnapshot" is now called a "Checkpoint", and "BlockExportStart/Stop" is now "BackupBegin/End" - flesh out more API descriptions - better documentation of proposed XML, for both checkpoints and backup Barring any major issues turned up during review, I've already starting to code this into libvirt with a goal of getting an implementation ready for review this month. Each domain will gain the ability to track a tree of Checkpoint objects (we've previously mentioned the term "system checkpoint" in the <domainsnapshot> XML as the combination of disk and RAM state; so I'll use the term "disk checkpoint" in prose as needed, to make it obvious that the checkpoints described here do not include RAM state). I will use the virDomainSnapshot API as a guide, meaning that we will track a tree of checkpoints where each checkpoint can have 0 or 1 parent checkpoints, in part because I plan to reuse a lot of the snapshot code as a starting point for implementing checkpoint tracking. Qemu does NOT track a relationship between internal snapshots, so libvirt has to manage the backing tree all by itself; by the same argument, if qemu does not add a parent relationship to dirty bitmaps, libvirt can probably manage everything itself by copying how it manages parent relationships between internal snapshots. However, I think it will be far easier for libvirt to exploit qemu dirty bitmaps if qemu DOES add bitmap tracking; particularly if qemu adds ways to easily compose a temporary bitmap that is the union of one bitmap plus a fixed number of its parents. Design-wise, libvirt will manage things so that there is only one enabled dirty-bitmap per qcow2 image at a time, when no backup operation is in effect. There is a notion of a current (or most recent) checkpoint; when a new checkpoint is created, that becomes the current one and the former checkpoint becomes the parent of the new one. If there is no current checkpoint, then there is no active dirty bitmap managed by libvirt. Representing things on a timeline, when a guest is first created, there is no dirty bitmap; later, the checkpoint "check1" is created, which in turn creates "bitmap1" in the qcow2 image for all changes past that point; when a second checkmark "check2" is created, a qemu transaction is used to create and enable the new "bitmap2" bitmap at the same time as disabling "bitmap1" bitmap. (Actually, it's probably easier to name the bitmap in the qcow2 file with the same name as the Checkpoint object being tracked in libvirt, but for discussion purposes, it's less confusing if I use separate names for now.) creation ....... check1 ....... check2 ....... active no bitmap bitmap1 bitmap2 When a user wants to create a backup, they select which point in time the backup starts from; the default value NULL represents a full backup (all content since disk creation to the point in time of the backup call, no bitmap is needed, use sync=full for push model or sync=none for the pull model); any other value represents the name of a checkpoint to use as an incremental backup (all content from the checkpoint to the point in time of the backup call; libvirt forms a temporary bitmap as needed, the uses sync=incremental for push model or sync=none plus exporting the bitmap for the pull model). For example, requesting an incremental backup from "check2" can just reuse "bitmap2", but requesting an incremental backup from "check1" requires the computation of the bitmap containing the union of "bitmap1" and "bitmap2". Libvirt will always create a new bitmap when starting a backup operation, whether or not the user requests that a checkpoint be created. Most users that want incremental backup sequences will create a new checkpoint every time they do a backup; the new bitmap that libvirt creates is then associated with that new checkpoint, and even after the backup operation completes, the new bitmap remains in the qcow2 file. But it is also possible to request a backup without a new checkpoint (it merely means that it is not possible to create a subsequent incremental backup from the backup just started); in that case, libvirt will have to take care of merging the new bitmap back into the previous one at the end of the backup operation. I think that it should be possible to run multiple backup operations in parallel in the long run. But in the interest of getting a proof of concept implementation out quickly, it's easier to state that for the initial implementation, libvirt supports at most one backup operation at a time (to do another backup, you have to wait for the current one to complete, or else abort and abandon the current one). As there is only one backup job running at a time, the existing virDomainGetJobInfo()/virDomainGetJobStats() will be able to report statistics about the job (insofar as such statistics are available). But in preparation for the future, when libvirt does add parallel job support, starting a backup job will return a job id; and presumably we'd add a new virDomainGetJobStatsByID() for grabbing statistics of an arbitrary (rather than the most-recently-started) job. Since live migration also acts as a job visible through virDomainGetJobStats(), I'm going to treat an active backup job and live migration as mutually exclusive. This is particularly true when we have a pull model backup ongoing: if qemu on the source is acting as an NBD server, you can't migrate away from that qemu and tell the NBD client to reconnect to the NBD server on the migration destination. So, to perform a migration, you have to cancel any pending backup operations. Conversely, if a migration job is underway, it will not be possible to start a new backup job until migration completes. However, we DO need to modify migration to ensure that any persistent bitmaps are migrated. I also think that in the long run, it should be possible to start a backup operation, and while it is still ongoing, create a new external snapshot, and still be able to coordinate the transfer of bitmaps from the old image to the new overlay. But for the first implementation, it's probably easiest to state that an ongoing backup prevents creation of a new snapshot. However, a current checkpoint (which means we DO have an active bitmap, even if there is no active backup) DOES need to be transfered to the new overlay, and conversely, a block commit job needs to merge all bitmaps from the old overlay to the backing file that is now becoming the active layer again. I don't know if qemu has primitives for this in place yet; and if it does not, the only conservative thing we can do in the initial implementation is to state that the use of checkpoints is exclusive from the use of snapshots (using one prevents the use of the other). Hopefully we don't have to stay in that state for long. For now, a user wanting guest I/O to be at a safe point can manually use virDomainFSFreeze()/virDomainBackupBegin()/virDomainFSThaw(); we may decide down the road to use the flags argument of virDomainBackupBegin() to provide automatic guest quiescing through one API (I'm not doing it right away, because we have to worry about undoing effects if we fail to thaw after starting the backup). So, to summarize, creating a backup will involve the following new APIs: /** * virDomainBackupBegin: * @domain: a domain object * @diskXml: description of storage to utilize and expose during * the backup, or NULL * @checkpointXml: description of a checkpoint to create, or NULL * @flags: not used yet, pass 0 * * Start a point-in-time backup job for the specified disks of a * running domain. * * A backup job is mutually exclusive with domain migration * (particularly when the job sets up an NBD export, since it is not * possible to tell any NBD clients about a server migrating between * hosts). For now, backup jobs are also mutually exclusive with any * other block job on the same device, although this restriction may * be lifted in a future release. Progress of the backup job can be * tracked via virDomainGetJobStats(). The job remains active until a * subsequent call to virDomainBackupEnd(), even if it no longer has * anything to copy. * * There are two fundamental backup approaches. The first, called a * push model, instructs the hypervisor to copy the state of the guest * disk to the designated storage destination (which may be on the * local file system or a network device); in this mode, the * hypervisor writes the content of the guest disk to the destination, * then emits VIR_DOMAIN_EVENT_ID_BLOCK_JOB_2 when the backup is * either complete or failed (the backup image is invalid if the job * is ended prior to the event being emitted). The second, called a * pull model, instructs the hypervisor to expose the state of the * guest disk over an NBD export; a third-party client can then * connect to this export, and read whichever portions of the disk it * desires. In this mode, there is no event; libvirt has to be * informed when the third-party NBD client is done and the backup * resources can be released. * * The @diskXml parameter is optional but usually provided, and * contains details about the backup, including which backup mode to * use, whether the backup is incremental from a previous checkpoint, * which disks participate in the backup, the destination for a push * model backup, and the temporary storage and NBD server details for * a pull model backup. If omitted, the backup attempts to default to * a push mode full backup of all disks, where libvirt generates a * filename for each disk by appending a suffix of a timestamp in * seconds since the Epoch. virDomainBackupGetXMLDesc() can be called * to actual values selected. For more information, see * formatcheckpoint.html#BackupAttributes. * * The @checkpointXml parameter is optional; if non-NULL, then libvirt * behaves as if virDomainCheckpointCreateXML() were called with * @checkpointXml, atomically covering the same guest state that will * be part of the backup. The creation of a new checkpoint allows for * future incremental backups. * * Returns a non-negative job id on success, or negative on failure. * This operation returns quickly, such that a user can choose to * start a backup job between virDomainFSFreeze() and * virDomainFSThaw() in order to create the backup while guest I/O is * quiesced. */ int virDomainBackupBegin(virDomainPtr domain, const char *diskXml, const char *checkpointXml, unsigned int flags); Note that this layout says that all disks participating in the backup job have share the same incremental checkpoint as their starting point (no way to have one backup job where disk A copies data since check1 while disk B copies data since check2). If we need the latter, then we could get rid of the 'incremental' parameter, and instead have each <disk> element within checkpointXml all out an optional <checkpoint> name as its starting point. Also, qemu supports exposing multiple disks through a single NBD server (you then connect multiple clients to the one server to grab state from each disk). So the NBD details are listed in parallel to the <disks>. Note that since a backup is NOT a guest-visible action, the backup job does not alter the normal <domain> XML. /** * virDomainBackupGetXMLDesc: * @domain: a domain object * @id: the id of an active backup job previously started with * virDomainBackupBegin() * @flags: not used yet, pass 0 * * In some cases, a user can start a backup job without supplying all * details, and rely on libvirt to fill in the rest (for example, * selecting the port used for an NBD export). This API can then be * used to learn what default values were chosen. * * Returns a NUL-terminated UTF-8 encoded XML instance, or NULL in * case of error. The caller must free() the returned value. */ char * virDomainBackupGetXMLDesc(virDomainPtr domain, int id, unsigned int flags); /** * virDomainBackupEnd: * @domain: a domain object * @id: the id of an active backup job previously started with * virDomainBackupBegin() * @flags: bitwise-OR of supported virDomainBackupEndFlags * * Conclude a point-in-time backup job @id on the given domain. * * If the backup job uses the push model, but the event marking that * all data has been copied has not yet been emitted, then the command * fails unless @flags includes VIR_DOMAIN_BACKUP_END_ABORT. If the * event has been issued, or if the backup uses the pull model, the * flag has no effect. * * Returns 0 on success and -1 on failure. */ int virDomainBackupEnd(virDomainPtr domain, int id, unsigned int flags); /** * virDomainCheckpointCreateXML: * @domain: a domain object * @xmlDesc: description of the checkpoint to create * @flags: bitwise-OR of supported virDomainCheckpointCreateFlags * * Create a new checkpoint using @xmlDesc on a running @domain. * Typically, it is more common to create a new checkpoint as part of * kicking off a backup job with virDomainBackupBegin(); however, it * is also possible to start a checkpoint without a backup. * * See formatcheckpoint.html#CheckpointAttributes document for more * details on @xmlDesc. * * If @flags includes VIR_DOMAIN_CHECKPOINT_CREATE_REDEFINE, then this * is a request to reinstate checkpoint metadata that was previously * discarded, rather than creating a new checkpoint. When redefining * checkpoint metadata, the current checkpoint will not be altered * unless the VIR_DOMAIN_CHECKPOINT_CREATE_CURRENT flag is also * present. It is an error to request the * VIR_DOMAIN_CHECKPOINT_CREATE_CURRENT flag without * VIR_DOMAIN_CHECKPOINT_CREATE_REDEFINE. * * If @flags includes VIR_DOMAIN_CHECKPOINT_CREATE_NO_METADATA, then * the domain's disk images are modified according to @xmlDesc, but * then the just-created checkpoint has its metadata deleted. This * flag is incompatible with VIR_DOMAIN_CHECKPOINT_CREATE_REDEFINE. * * Returns an (opaque) new virDomainCheckpointPtr on success, or NULL * on failure. */ virDomainCheckpointPtr virDomainCheckpointCreateXML(virDomainPtr domain, const char *xmlDesc, unsigned int flags); /** * virDomainCheckpointDelete: * @checkpoint: the checkpoint to remove * @flags: not used yet, pass 0 * @flags: bitwise-OR of supported virDomainCheckpointDeleteFlags * * Removes a checkpoint from the domain. * * When removing a checkpoint, the record of which portions of the * disk were dirtied after the checkpoint will be merged into the * record tracked by the parent checkpoint, if any. Likewise, if the * checkpoint being deleted was the current checkpoint, the parent * checkpoint becomes the new current checkpoint. * * If @flags includes VIR_DOMAIN_CHECKPOINT_DELETE_METADATA_ONLY, then * any checkpoint metadata tracked by libvirt is removed while keeping * the checkpoint contents intact; if a hypervisor does not require * any libvirt metadata to track checkpoints, then this flag is * silently ignored. * * Returns 0 on success, -1 on error. */ int virDomainCheckpointDelete(virDomainCheckpointPtr checkpoint, unsigned int flags); // Many additional functions copying heavily from virDomainSnapshot*: virDomainCheckpointList(virDomainPtr domain, virDomainCheckpointPtr **checkpoints, unsigned int flags); virDomainCheckpointGetXMLDesc(virDomainCheckpointPtr checkpoint, unsigned int flags); virDomainCheckpointPtr virDomainCheckpointLookupByName(virDomainPtr domain, const char *name, unsigned int flags); const char * virDomainCheckpointGetName(virDomainCheckpointPtr checkpoint); virDomainPtr virDomainCheckpointGetDomain(virDomainCheckpointPtr checkpoint); virConnectPtr virDomainCheckpointGetConnect(virDomainCheckpointPtr checkpoint); int virDomainHasCurrentCheckpoint(virDomainPtr domain, unsigned int flags); virDomainCheckpointPtr virDomainCheckpointCurrent(virDomainPtr domain, unsigned int flags); virDomainCheckpointPtr virDomainCheckpointGetParent(virDomainCheckpointPtr checkpoint, unsigned int flags); int virDomainCheckpointIsCurrent(virDomainCheckpointPtr checkpoint, unsigned int flags); int virDomainCheckpointRef(virDomainCheckpointPtr checkpoint); int virDomainCheckpointFree(virDomainCheckpointPtr checkpoint); int virDomainCheckpointListChildren(virDomainCheckpointPtr checkpoint, virDomainCheckpointPtr **children, unsigned int flags); Notably, none of the older racy list functions, like virDomainSnapshotNum, virDomainSnapshotNumChildren, or virDomainSnapshotListChildrenNames; also, for now, there is no revert support like virDomainSnapshotRevert. Eventually, if we add a way to roll back to the state recorded in an earlier bitmap, we'll want to tell libvirt that it needs to create a new bitmap as a child of an existing (non-current) checkpoint. That is, if we have: check1 .... check2 .... active bitmap1 bitmap2 and created a backup at the same time as check2, then when we later roll back to the state of that backup, we would want to end writes to bitmap2 and declare that check2 is no longer current, and create a new current check3 with associated bitmap3 and parent check1 to track all writes since the point of the revert. Until then, I don't think it's possible to have more than one child without manually using the REDEFINE flag to create such scenarios; but the API should not lock us out of supporting multiple children in the future. Here's my proposal for user-facing XML documentation, based on formatsnapshot.html.in: <?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE html> <html xmlns="http://www.w3.org/1999/xhtml"> <body> <h1>Checkpoint and Backup XML format</h1> <ul id="toc"></ul> <h2><a id="CheckpointAttributes">Checkpoint XML</a></h2> <p> Libvirt is able to facilitate incremental backups by tracking disk checkpoints, or points in time against which it is easy to compute which portion of the disk has changed. Given a full backup (a backup created from the creation of the disk to a given point in time, coupled with the creation of a disk checkpoint at that time), and an incremental backup (a backup created from just the dirty portion of the disk between the first checkpoint and the second backup operation), it is possible to do an offline reconstruction of the state of the disk at the time of the second backup, without having to copy as much data as a second full backup would require. Most disk checkpoints are created in concert with a backup, via <code>virDomainBackupBegin()</code>; however, libvirt also exposes enough support to create disk checkpoints independently from a backup operation, via <code>virDomainCheckpointCreateXML()</code>. </p> <p> Attributes of libvirt checkpoints are stored as child elements of the <code>domaincheckpoint</code> element. At checkpoint creation time, normally only the <code>name</code>, <code>description</code>, and <code>disks</code> elements are settable; the rest of the fields are ignored on creation, and will be filled in by libvirt in for informational purposes by <code>virDomainCheckpointGetXMLDesc()</code>. However, when redefining a checkpoint, with the <code>VIR_DOMAIN_CHECKPOINT_CREATE_REDEFINE</code> flag of <code>virDomainCheckpointCreateXML()</code>, all of the XML described here is relevant. </p> <p> Checkpoints are maintained in a hierarchy. A domain can have a current checkpoint, which is the most recent checkpoint compared to the current state of the domain (although a domain might have checkpoints without a current checkpoint, if checkpoints have been deleted in the meantime). Creating or reverting to a checkpoint sets that checkpoint as current, and the prior current checkpoint is the parent of the new checkpoint. Branches in the hierarchy can be formed by reverting to a checkpoint with a child, then creating another checkpoint. </p> <p> The top-level <code>domaincheckpoint</code> element may contain the following elements: </p> <dl> <dt><code>name</code></dt> <dd>The name for this checkpoint. If the name is specified when initially creating the checkpoint, then the checkpoint will have that particular name. If the name is omitted when initially creating the checkpoint, then libvirt will make up a name for the checkpoint, based on the time when it was created. </dd> <dt><code>description</code></dt> <dd>A human-readable description of the checkpoint. If the description is omitted when initially creating the checkpoint, then this field will be empty. </dd> <dt><code>disks</code></dt> <dd>On input, this is an optional listing of specific instructions for disk checkpoints; it is needed when making a checkpoint on only a subset of the disks associated with a domain (in particular, since qemu checkpoints require qcow2 disks, this element may be needed on input for excluding guest disks that are not in qcow2 format); if omitted on input, then all disks participate in the checkpoint. On output, this is fully populated to show the state of each disk in the checkpoint. This element has a list of <code>disk</code> sub-elements, describing anywhere from one to all of the disks associated with the domain. <dl> <dt><code>disk</code></dt> <dd>This sub-element describes the checkpoint properties of a specific disk. The attribute <code>name</code> is mandatory, and must match either the <code><target dev='name'/></code> or an unambiguous <code><source file='name'/></code> of one of the <a href="formatdomain.html#elementsDisks">disk devices</a> specified for the domain at the time of the checkpoint. The attribute <code>checkpoint</code> is optional on input; possible values are <code>no</code> when the disk does not participate in this checkpoint; or <code>bitmap</code> if the disk will track all changes since the creation of this checkpoint via a bitmap, in which case another attribute <code>bitmap</code> will be the name of the tracking bitmap (defaulting to the checkpoint name). </dd> </dl> </dd> <dt><code>creationTime</code></dt> <dd>The time this checkpoint was created. The time is specified in seconds since the Epoch, UTC (i.e. Unix time). Readonly. </dd> <dt><code>parent</code></dt> <dd>The parent of this checkpoint. If present, this element contains exactly one child element, name. This specifies the name of the parent checkpoint of this one, and is used to represent trees of checkpoints. Readonly. </dd> <dt><code>domain</code></dt> <dd>The inactive <a href="formatdomain.html">domain configuration</a> at the time the checkpoint was created. Readonly. </dd> </dl> <h2><a id="BackupAttributes">Backup XML</a></h2> <p> Creating a backup, whether full or incremental, is done via <code>virDomainBackupBegin()</code>, which takes an XML description of the actions to perform. There are two general modes for backups: a push mode (where the hypervisor writes out the data to the destination file, which may be local or remote), and a pull mode (where the hypervisor creates an NBD server that a third-party client can then read as needed, and which requires the use of temporary storage, typically local, until the backup is complete). </p> <p> The instructions for beginning a backup job are provided as attributes and elements of the top-level <code>domainbackup</code> element. This element includes an optional attribute <code>mode</code> which can be either "push" or "pull" (default push). Where elements are optional on creation, <code>virDomainBackupGetXMLDesc()</code> can be used to see the actual values selected (for example, learning which port the NBD server is using in the pull model, or what file names libvirt generated when none were supplied). The following child elements are supported: </p> <dl> <dt><code>incremental</code></dt> <dd>Optional. If this element is present, it must name an existing checkpoint of the domain, which will be used to make this backup an incremental one (in the push model, only changes since the checkpoint are written to the destination; in the pull model, the NBD server uses the NBD_OPT_SET_META_CONTEXT extension to advertise to the client which portions of the export contain changes since the checkpoint). If omitted, a full backup is performed. </dd> <dt><code>server</code></dt> <dd>Present only for a pull mode backup. Contains the same attributes as the <code>protocol</code> element of a disk attached via NBD in the domain (such as transport, socket, name, port, or tls), necessary to set up an NBD server that exposes the content of each disk at the time the backup started. </dd> <dt><code>disks</code></dt> <dd>This is an optional listing of instructions for disks participating in the backup (if omitted, all disks participate, and libvirt attempts to generate filenames by appending the current timestamp as a suffix). When provided on input, disks omitted from the list do not participate in the backup. On output, the list is present but contains only the disks participating in the backup job. This element has a list of <code>disk</code> sub-elements, describing anywhere from one to all of the disks associated with the domain. <dl> <dt><code>disk</code></dt> <dd>This sub-element describes the checkpoint properties of a specific disk. The attribute <code>name</code> is mandatory, and must match either the <code><target dev='name'/></code> or an unambiguous <code><source file='name'/></code> of one of the <a href="formatdomain.html#elementsDisks">disk devices</a> specified for the domain at the time of the checkpoint. The optional attribute <code>type</code> can be <code>file</code>, <code>block</code>, or <code>networks</code>, similar to a disk declaration for a domain, controls what additional sub-elements are needed to describe the destination (such as <code>protocol</code> for a network destination). In push mode backups, the primary subelement is <code>target</code>; in pull mode, the primary sublement is <code>scratch</code>; but either way, the primary sub-element describes the file name to be used during the backup operation, similar to the <code>source</code> sub-element of a domain disk. An optional sublement <code>driver</code> can also be used to specify a destination format different from qcow2. </dd> </dl> </dd> </dl> <h2><a id="example">Examples</a></h2> <p>Using this XML to create a checkpoint of just vda on a qemu domain with two disks and a prior checkpoint:</p> <pre> <domaincheckpoint> <description>Completion of updates after OS install</description> <disks> <disk name='vda' checkpoint='bitmap'/> <disk name='vdb' checkpoint='no'/> </disks> </domaincheckpoint></pre> <p>will result in XML similar to this from <code>virDomainCheckpointGetXMLDesc()</code>:</p> <pre> <domaincheckpoint> <name>1525889631</name> <description>Completion of updates after OS install</description> <creationTime>1525889631</creationTime> <parent> <name>1525111885</name> </parent> <disks> <disk name='vda' checkpoint='bitmap' bitmap='1525889631'/> <disk name='vdb' checkpoint='no'/> </disks> <domain> <name>fedora</name> <uuid>93a5c045-6457-2c09-e56c-927cdf34e178</uuid> <memory>1048576</memory> ... <devices> <disk type='file' device='disk'> <driver name='qemu' type='qcow2'/> <source file='/path/to/file1'/> <target dev='vda' bus='virtio'/> </disk> <disk type='file' device='disk' snapshot='external'> <driver name='qemu' type='raw'/> <source file='/path/to/file2'/> <target dev='vdb' bus='virtio'/> </disk> ... </devices> </domain> </domaincheckpoint></pre> <p>With that checkpoint created, the qcow2 image is now tracking all changes that occur in the image since the checkpoint via the persistent bitmap named <code>1525889631</code>. Now, we can make a subsequent call to <code>virDomainBackupBegin()</code> to perform an incremental backup of just this data, using the following XML to start a pull model NBD export of the vda disk: </p> <pre> <domainbackup mode="pull"> <incremental>1525889631</incremental> <server transport="unix" socket="/path/to/server"/> <disks/> <disk name='vda' type='file'/> <scratch file=/path/to/file1.scratch'/> </disk> </disks/> </domainbackup> </pre> </body> </html> -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3266 Virtualization: qemu.org | libvirt.org

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[libvirt] Likely build race, "/usr/bin/ld: cannot find -lvirt"
by Ian Jackson 13 Jun '18

13 Jun '18

tl;dr: I think there is a bug in libvirt's build system which, with low probability, causes a build failure containing this message: /usr/bin/ld: cannot find -lvirt Complete build logs of two attempts: http://logs.test-lab.xenproject.org/osstest/logs/123046/build-i386-libvirt/… http://logs.test-lab.xenproject.org/osstest/logs/123096/build-i386-libvirt/… Snippet from 123046 containing the error is enclosed below. Longer explanation: I have two new machines for the Xen Project CI, which I am trying to commission. As part of commissioning I run a complete test run (a "flight" in osstest terminology) on just those new hosts. The i386 libvirt build failed: http://logs.test-lab.xenproject.org/osstest/logs/123046/build-i386-libvirt/… Everything else that would be expected to work was fine. The test programme was identical to flight 122815, except that that ran on other hosts in the test farm (and, there, it passed). The error is the kind of error one sees with missing dependencies in parallel builds, etc. I wanted to have some 32-bit libvirt tests actually run, so I reran a new flight containing the relevant parts. That failed too in a very similar way: http://logs.test-lab.xenproject.org/osstest/logs/123096/build-i386-libvirt/… The two machines are Dell R230s (and therefore hardly unusual). The main novelty of these machines is that the firmware is UEFI booting in UEFI mode. I doubt that has anything to do with it. The host, including compiler, is Debian jessie i386. As you can see from the log, we were trying to build libvirt 764a7483f189e6de841163647c14296e693dbb2e What may be less obvious is that we were trying to build it against xen.git#0306a1311d02ea52b4a9a9bc339f8bab9354c5e3. http://logs.test-lab.xenproject.org/osstest/logs/123064/build-i386-libvirt/… http://logs.test-lab.xenproject.org/osstest/logs/123046/build-i386/info.html Does this seem like a likely explanation ? Have other people experienced occasional problems with make -j ? If someone wants to suggest a patch that might fix it I can test it. In the meantime I have set off a number of new attempts, to try to guess the failure probability, and also one attempt on other hosts to check that nothing unexpected was broken. Ian. /usr/bin/ld: cannot find -lvirt /usr/bin/ld: cannot find -lvirt /bin/mkdir -p '/home/osstest/build.123046.build-i386-libvirt/dist/usr/local/lib/libvirt/storage-backend' /bin/bash ../libtool --mode=install /usr/bin/install -c libvirt_storage_backend_fs.la libvirt_storage_backend_logical.la libvirt_storage_backend_scsi.la libvirt_storage_backend_mpath.la '/home/osstest/build.123046.build-i386-libvirt/dist/usr/local/lib/libvirt/storage-backend' libtool: install: warning: relinking `libvirt_storage_backend_fs.la' libtool: install: (cd /home/osstest/build.123046.build-i386-libvirt/libvirt/src; /bin/bash /home/osstest/build.123046.build-i386-libvirt/libvirt/libtool --silent --tag CC --mode=relink gcc -std=gnu99 -I./conf -I/usr/include/libxml2 -fno-common -W -Waddress -Waggressive-loop-optimizations -Wall -Wattributes -Wbad-function-cast -Wbuiltin-macro-redefined -Wcast-align -Wchar-subscripts -Wclobbered -Wcomment -Wcomments -Wcoverage-mismatch -Wcpp -Wdate-time -Wdeprecated-declarations -Wdiv-by-zero -Wdouble-promotion -Wempty-body -Wendif-labels -Wextra -Wformat-contains-nul -Wformat-extra-args -Wformat-security -Wformat-y2k -Wformat-zero-length -Wfree-nonheap-object -Wignored-qualifiers -Wimplicit -Wimplicit-function-declaration -Wimplicit-int -Winit-self -Winline -Wint-to-pointer-cast -Winvalid-memory-model -Winvalid-pch -Wjump-misses-init -Wlogical-op -Wmain -Wmaybe-uninitialized -Wmemset-transposed-args -Wmissing-braces -Wmissing-declarations -Wmissing-field-initializers -Wmissing-include-dirs -Wmissing-parameter-type -Wmissing-prototypes -Wmultichar -Wnarrowing -Wnested-externs -Wnonnull -Wold-style-declaration -Wold-style-definition -Wopenmp-simd -Woverflow -Woverride-init -Wpacked-bitfield-compat -Wparentheses -Wpointer-arith -Wpointer-sign -Wpointer-to-int-cast -Wpragmas -Wpsabi -Wreturn-local-addr -Wreturn-type -Wsequence-point -Wshadow -Wsizeof-pointer-memaccess -Wstrict-aliasing -Wstrict-prototypes -Wsuggest-attribute=const -Wsuggest-attribute=format -Wsuggest-attribute=noreturn -Wsuggest-attribute=pure -Wswitch -Wsync-nand -Wtrampolines -Wtrigraphs -Wtype-limits -Wuninitialized -Wunknown-pragmas -Wunused -Wunused-but-set-parameter -Wunused-but-set-variable -Wunused-function -Wunused-label -Wunused-local-typedefs -Wunused-parameter -Wunused-result -Wunused-value -Wunused-variable -Wvarargs -Wvariadic-macros -Wvector-operation-performance -Wvolatile-register-var -Wwrite-strings -Wnormalized=nfc -Wno-sign-compare -Wjump-misses-init -Wswitch-enum -Wno-format-nonliteral -fstack-protector-strong -fexceptions -fasyn chronous-unwind-tables -fipa-pure-const -Wno-suggest-attribute=pure -Wno-suggest-attribute=const -Werror -Wframe-larger-than=4096 -g -I/home/osstest/build.123046.build-i386-libvirt/xendist/usr/local/include/ -DLIBXL_API_VERSION=0x040400 -module -avoid-version -Wl,-z -Wl,nodelete -export-dynamic -Wl,-z -Wl,relro -Wl,-z -Wl,now -Wl,--no-copy-dt-needed-entries -g -L/home/osstest/build.123046.build-i386-libvirt/xendist/usr/local/lib/ -Wl,-rpath-link=/home/osstest/build.123046.build-i386-libvirt/xendist/usr/local/lib/ -o libvirt_storage_backend_fs.la -rpath /usr/local/lib/libvirt/storage-backend storage/libvirt_storage_backend_fs_la-storage_backend_fs.lo libvirt.la ../gnulib/lib/libgnu.la -ldl -inst-prefix-dir /home/osstest/build.123046.build-i386-libvirt/dist) collect2: error: ld returned 1 exit status Makefile:6410: recipe for target 'install-lockdriverLTLIBRARIES' failed libtool: install: error: relink `lockd.la' with the above command before installing it make[3]: *** [install-lockdriverLTLIBRARIES] Error 1 make[3]: *** Waiting for unfinished jobs.... /usr/bin/ld: cannot find -lvirt

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