Commit Graph

36228 Commits

Author SHA1 Message Date
Ján Tomko
06160f6708 qemu: eliminate ret variable in qemuExtTPMStartEmulator
Now that the cleanup section is empty, eliminate the cleanup
label as well as the 'ret' variable.

Signed-off-by: Ján Tomko <jtomko@redhat.com>
Reviewed-by: Peter Krempa <pkrempa@redhat.com>
2020-01-28 13:32:27 +01:00
Ján Tomko
ebe9c31f41 qemu: use g_auto in qemuExtTPMStartEmulator
Use the g_auto macros wherever possible to eliminate the cleanup
section.

Signed-off-by: Ján Tomko <jtomko@redhat.com>
Reviewed-by: Peter Krempa <pkrempa@redhat.com>
2020-01-28 13:32:27 +01:00
Ján Tomko
3efdbae5bf conf: use virXMLFormatElement in virDomainFSDefFormat
Use the virXMLFormatElement helper to format the driver element
to simplify adding further sub-elements.

Signed-off-by: Ján Tomko <jtomko@redhat.com>
Reviewed-by: Peter Krempa <pkrempa@redhat.com>
2020-01-28 10:31:41 +01:00
Andrea Bolognani
3a3a85c529 gitdm: Add missing entries
A few new companies and individuals contributed to libvirt since
the last time the gitdm configuration was updated.

Signed-off-by: Andrea Bolognani <abologna@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
2020-01-27 18:04:06 +01:00
Andrea Bolognani
c8a3a5d79b qemu_shim: Update temporary directory template
The template still references libvirt-qemu-shim, which was at one
point the name used to refer to what we now know as virt-qemu-run.

Signed-off-by: Andrea Bolognani <abologna@redhat.com>
2020-01-27 17:57:43 +01:00
Andrea Bolognani
7dca28e229 qemu_shim: Fix typos
Signed-off-by: Andrea Bolognani <abologna@redhat.com>
2020-01-27 17:57:08 +01:00
Andrea Bolognani
761163fbda docs: Fix link to virt-qemu-run(1)
Signed-off-by: Andrea Bolognani <abologna@redhat.com>
2020-01-27 17:57:02 +01:00
Ján Tomko
c07ef7c563 qemu: snapshot: go through cleanup on error
A recent commit added an error check for too-nested backing chains
followed by a return, even though errors above jump to cleanup.

Signed-off-by: Ján Tomko <jtomko@redhat.com>
Fixes: b168fa88b8
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Andrea Bolognani <abologna@redhat.com>
2020-01-27 17:36:05 +01:00
Ján Tomko
26a42e7315 qemu_shim: cosmetic fixes
Remove bogus G_GNUC_UNUSED attribute and add a missing space.

Signed-off-by: Ján Tomko <jtomko@redhat.com>
Fixes: d600667278
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Andrea Bolognani <abologna@redhat.com>
2020-01-27 17:36:05 +01:00
Ján Tomko
fe8921c27b docs: fix since version in driver documentation
Also one stray angle bracket.

Signed-off-by: Ján Tomko <jtomko@redhat.com>
Fixes: 068efae5b1
Fixes: 3e9076e777
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Andrea Bolognani <abologna@redhat.com>
2020-01-27 17:36:05 +01:00
Ján Tomko
b0b94a8d32 docs: fix virt-qemu-run man page
Fix a documentation generation error:
System Message: WARNING/2 (<stdin>, line 15); backlink
Inline literal start-string without end-string.

As well as the 'independant' typo.

Signed-off-by: Ján Tomko <jtomko@redhat.com>
Fixes: d600667278
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Andrea Bolognani <abologna@redhat.com>
2020-01-27 17:36:05 +01:00
Peter Krempa
d9dfc1f7de qemu: checkpoint: Extract calculation of bitmap merging for checkpoint deletion
This will allow some testing before refactoring.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2020-01-27 15:28:49 +01:00
Peter Krempa
6796194a28 qemu: checkpoint: Introduce helper to find checkpoint disk definition in parents
The algorithm is used in two places to find the parent checkpoint object
which contains given disk and then uses data from the disk. Additionally
the code is written in a very non-obvious way. Factor out the lookup of
the disk into a function which also simplifies the callers.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2020-01-27 15:28:49 +01:00
Peter Krempa
180b3422e9 qemu: domain: Remove unused qemuDomainDiskNodeFormatLookup
The function has no users now and there's no need for it as the common
pattern is to look up the whole disk object anyways.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2020-01-27 15:28:49 +01:00
Peter Krempa
f19248a139 qemu: checkpoint: tolerate missing disks on checkpoint deletion
If a disk is unplugged and then the user tries to delete a checkpoint
the code would try to use NULL node name as it was not checked.

Fix this by fetching the whole disk definition object and verifying it
was found.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2020-01-27 15:28:49 +01:00
Peter Krempa
7973f7d792 qemu: checkpoint: Use disk definition directly when creating checkpoint
Lookup the whole disk definition rather than just the node name.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2020-01-27 15:28:49 +01:00
Peter Krempa
f3e0a45a00 qemu: checkpoint: rename disk->chkdisk in qemuCheckpointAddActions
Upcoming patches will also use the domain disk definition. Rename disk
to chkdisk for clarity.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2020-01-27 15:28:49 +01:00
Peter Krempa
a303e8ea47 qemu: checkpoint: rename disk->chkdisk in qemuCheckpointDiscardBitmaps
Upcoming patches will also use the domain disk definition. Rename disk
to chkdisk for clarity.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2020-01-27 15:28:49 +01:00
Peter Krempa
44e1b85717 qemu: checkpoint: split out checkpoint deletion bitmaps
qemuCheckpointDiscard is a massive function that can be separated into
smaller bits. Extract the part that actually modifies the disk from the
metadata handling.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2020-01-27 15:28:49 +01:00
Peter Krempa
606dc66b09 qemu: checkpoint: Store whether deleted checkpoint is current in a variable
Avoid two computations by using a boolean.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2020-01-27 15:28:49 +01:00
Peter Krempa
99eebcfe48 tests: qemu: Remove prehistoric machine types from faked data tests
qemu-5.0 will drop pre pc-1.0 machine types. Remove them from our
faked capabilities test suite. If a feature depends on a machine type it
shall be tested with real data and not with this hack.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
2020-01-27 14:55:03 +01:00
Peter Krempa
f6a36dffc2 tests: qemuxml2xml: Remove prehistoric machine types from legacy tests
None of the tests depend on anything that the machine type would
influence. This will allow us to drop the very old machine type from the
non-real-data tests. If something depends on the machine type it should
be tested with real data rather than this hack.

Note that these tests are run only in the XML->XML suite because the
XML->argv suite doesn't work with the network driver.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
2020-01-27 14:55:03 +01:00
Peter Krempa
de723a29a3 tests: qemuxml: Remove prehistoric machine types from legacy tests
None of the tests depend on anything that the machine type would
influence. This will allow us to drop the very old machine type from the
non-real-data tests. If something depends on the machine type it should
be tested with real data rather than this hack.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
2020-01-27 14:55:03 +01:00
Peter Krempa
0f73d707ea tests: Add caps for upcoming qemu-5.0
Based on upstream commit 3e08b2b9cb64. This version already dropped the
pre-historic machine types and supports only machine types starting from
'pc-1.0'.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
2020-01-27 14:55:03 +01:00
Peter Krempa
30518a3b6a tests: qemuxml: Purge prehistoric machine type 'pc-0.13' from "latest" tests
Remove the old machine type which will be dropped in the upcomming
qemu-5.0 release from tests used against the most recent capabilities
data.

None of the modified tests really cares about the actual machine type.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
2020-01-27 14:55:03 +01:00
Peter Krempa
ec0db69c86 tests: qemu: Don't add fake machine types when testing with real data
Skip the step of adding all of the fake machine types which are required
for the legacy tests in case when we are testing with real capabilities.

Faking any data in the real capabilities undermines the point of testing
with real capabilities.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
2020-01-27 14:55:03 +01:00
Peter Krempa
60b580b949 qemu: capabilities: Add accessor to qemu caps machine types presence
Test code will need to know whether the virQEMUCaps object contains any
machine types already. Add a helper and expose it via 'qemu_capspriv.h'.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
2020-01-27 14:55:03 +01:00
Peter Krempa
3b8feb4793 qemu: capabilities: Replace aliased machine type by copy of the canonical machine
The previous approac of just purging the alias combined with the fact
that we filled in fake machine types in the test data meant that if a
test case used an alias machine type such as 'pc' or 'q35' it would not
properly resolve to the actual data returned by qemu.

This started to be a problem since the CPU driver now looks at the
default CPU reported with the machine type.

This patch replaces the original approach of just removing the alias by
replacing it with a copy of the machine type data which the type would
alias to. This means that we are using the real data while we don't
modify the test output after every qemu upgrade.

Additionally this change will allow us to drop adding the fake machine
types later.

The test fallout is from actually excercising the CPU driver with
actual data.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
2020-01-27 14:55:03 +01:00
Peter Krempa
bb61230992 qemu: capabilities: Extract code from virQEMUCapsStripMachineAliases
Separate out the internals as they will become more complex soon.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
2020-01-27 14:55:03 +01:00
Peter Krempa
0b9d1a8073 qemu: domain: Validate that machine type is supported by qemu
Every supported qemu is able to return the list of machine types it
supports so we can start validating it against that list. The advantage
is a better error message, and the change will also prevent having stale
test data.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
2020-01-27 14:55:03 +01:00
Peter Krempa
cb5a89c115 tests: qemu: Add machine types used by the test code to fake capabilities
Enumerate all missing machine types for all missing architectures for
the fake capabilities used in many existing tests. This will allow
stricter validation whether qemu actually supports given machine type
since we already have some behaviour dependant on the actual machine
type.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
2020-01-27 14:55:03 +01:00
Peter Krempa
6d9caaaef5 tests: qemuxml: Use existing machine type in 'iothreads-virtio-scsi-ccw' case
Use the 's390-ccw-virtio' machine type which is actually supported by
the qemu we gathered the test data from.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
2020-01-27 14:55:03 +01:00
Peter Krempa
9517890f7c tests: qemuxml2argv: Use proper replacement for 'pc-i440fx-wily' machine
This machine type comes from downstream ubuntu 15.10. Replace it with a
somewhat equivalent qemu-2.3 machine type as we do have test data for
that.

The change allows the CPU code to pick a proper default CPU in the
'-latest' cases.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
2020-01-27 14:55:03 +01:00
Peter Krempa
ccd4231149 tests: qemuxml2argv: Use existing non-virt machine in 'aarch64-gic-not-virt'
Use 'versatilepb' instead of a fake 'non-virt' machine type.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
2020-01-27 14:55:03 +01:00
Peter Krempa
f9bb79ff41 tests: qemuxml2argv: Remove downstream machine type in 'controller-order' case
Use 'pc' instead of ancient 'rhel-6.1'.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
2020-01-27 14:55:03 +01:00
Peter Krempa
99dcdf505e tests: qemuxml2argv: Use existing machine type for 'numatune-distances' case
Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
2020-01-27 14:55:03 +01:00
Peter Krempa
d29ee7c124 tests: qemu: Unify fake machine types filled in for KVM and TCG caps of x86_64
For testing with synthetic capabilities we pre-fill the qemu
capabilities with some machine types. Historically there were two arrays
for KVM and TCG but that's not necessary. Make both instances of x86_64
data share the same array as the other architectures do.

This will later on simplify filling in all the other machine types which
are required for the test suite.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
2020-01-27 14:55:03 +01:00
Peter Krempa
8dc3c6ea9f tests: qemuxml: Fix and enable default-video-type* tests
The tests prefixed default-video* were enabled only for the xml2xml
testing and used impossible configurations.

Enable them for xml2argv testing fix them:
1) aarch64: remove pointless cpu mode
2) s390x: remove pointless cpu and use existing machine type
3) riscv: remove pointless cpu
4) x86: remove pointless cpu and use existing machine type
5) ppc65: use correct machine type and enable USB

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
2020-01-27 14:55:03 +01:00
Peter Krempa
44d32a0ac7 tests: qemuxml2argv: Modernize tpm-passthrough tests
XML->XML testing uses DO_TEST_CAPS_LATEST so use it also for the
XML->argv testing. Additionally use the same more modern machine type
in both tests.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
2020-01-27 14:55:03 +01:00
Peter Krempa
03a2235ab7 tests: qemuxml2xml: Modernize 'disk-cache' test
Mirror what's done in the xml2argv test and use recent capabilities.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
2020-01-27 14:55:03 +01:00
Peter Krempa
66cba5c065 tests: qemuxml2argv: Use 64 bit qemu binary and 1.5 machine type in 'disk-cache' case
The data is tested against the latest qemu binaries so we should use the
proper architecture. Also the test is used against data from qemu 1.5.3
and thus we should use a machine type that qemu supported.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
2020-01-27 14:55:03 +01:00
Daniel P. Berrangé
82dd011dbb qemu: fix linking virt-qemu-run on some distros
Debian/Ubuntu linkers are more strict that other distros requiring glib
to be linked explicitly.

macOS needs -export-dynamic instead of -Wl,--export-dynamic

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
2020-01-27 13:44:56 +00:00
Daniel P. Berrangé
9a5bafd329 bhyve: add 'root' parameter to driver initializer
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
2020-01-27 13:44:56 +00:00
Peter Krempa
b168fa88b8 qemu: snapshot: Prevent too-nested domain XML when doing inactive snapshot
Similarly to 510d154a0b we need to prevent
doing too deeply nested backing chains and reject them with a sane error
message.

Add a loop to go through the snapshots prior to attempting actually
creating them to prevent some possible inconsistent scenarios.

We don't need to do it when reusing backing chains as we'll be
re-detecting the backing chain in that case anyways.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2020-01-27 14:02:01 +01:00
Peter Krempa
8e9e73a984 qemu: snapshot: Always rewrite backingStore data when reusing existing images
Don't adopt the backing store data when reusing images provided by the
user. This will force a backing chain re-probe as users might have
passed in something unexpected in the overlay where our view of the
backing chain would not correspond.

This is done only for inactive snapshots as there we have way less
verification.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2020-01-27 14:02:01 +01:00
Daniel P. Berrangé
201156ec6e docs: add pages to support Go module package resolution
Currently the libvirt Go modules are accessed by applications using
their github repository URLs. This is undesirable as we don't want
applications to have a direct dependancy on a specific source repo
location. We want to enable applications to use the Go packages via
the libvirt.org namespace.

When you do "go get libvirt.org/libvirt-go", the Go client will do an
HTTPS request to that URL, and parse the HTML content to look for a
<meta> tag which tells it where to the find the GIT repository.

   https://golang.org/cmd/go/#hdr-Remote_import_paths

This adds two pages to support this Go module resolution. They are
not linked from anywhere as we don't expect users to actually look
at them. If someone does happen upon them, there's some boilerplate
text to send them off to godoc.org for API documentation.

Since the pages we're adding have a .html extension, we will also
use a small apache config tweak on the server

    RewriteEngine on
    RewriteRule ^/libvirt-go$ /libvirt-go.html [L]
    RewriteRule ^/libvirt-go-xml$ /libvirt-go-xml.html [L]

Reviewed-by: Jiri Denemark <jdenemar@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
2020-01-27 11:51:46 +00:00
Daniel P. Berrangé
d600667278 qemu: introduce a new "virt-qemu-run" program
The previous "QEMU shim" proof of concept was taking an approach of only
caring about initial spawning of the QEMU process. It was then
registered with the libvirtd daemon who took over management of it. The
intent was that later libvirtd would be refactored so that the shim
retained control over the QEMU monitor and libvirt just forwarded APIs
to each shim as needed. This forwarding of APIs would require quite alot
of significant refactoring of libvirtd to achieve.

This impl thus takes a quite different approach, explicitly deciding to
keep the VMs completely separate from those seen & managed by libvirtd.
Instead it uses the new "qemu:///embed" URI scheme to embed the entire
QEMU driver in the shim, running with a custom root directory.

Once the driver is initialization, the shim starts a VM and then waits
to shutdown automatically when QEMU shuts down, or should kill QEMU if
it is terminated itself. This ought to use the AUTO_DESTROY feature but
that is not yet available in embedded mode, so we rely on installing a
few signal handlers to gracefully kill QEMU. This isn't reliable if
we crash of course, but you can restart with the same root dir.

Note this program does not expose any way to manage the QEMU process,
since there's no RPC interface enabled. It merely starts the VM and
cleans up when the guest shuts down at the end. This program is
installed to /usr/bin/virt-qemu-run enabling direct use by end users.
Most use cases will probably want to integrate the concept directly
into their respective application codebases. This standalone binary
serves as a nice demo though, and also provides a way to measure
performance of the startup process quite simply.

Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
2020-01-27 11:05:02 +00:00
Daniel P. Berrangé
3e9076e777 secrets: add support for running secret driver in embedded mode
This enables support for running the secret driver embedded to the
calling application process using a URI:

   secret:///embed?root=/some/path

When using the embedded mode with a root=/var/tmp/embed, the
driver will use the following paths:

       configDir: /var/tmp/embed/etc/secrets
        stateDir: /var/tmp/embed/run/secrets

These are identical whether the embedded driver is privileged
or unprivileged.

This compares with the system instance which uses

       configDir: /etc/libvirt/secrets
        stateDir: /var/lib/libvirt/secrets

When an embedded instance of the secret driver is open, any other
embedded drivers will automatically use the embedded secret driver.

Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
2020-01-27 11:04:29 +00:00
Daniel P. Berrangé
068efae5b1 qemu: add support for running QEMU driver in embedded mode
This enables support for running QEMU embedded to the calling
application process using a URI:

   qemu:///embed?root=/some/path

Note that it is important to keep the path reasonably short to
avoid risk of hitting the limit on UNIX socket path names
which is 108 characters.

When using the embedded mode with a root=/var/tmp/embed, the
driver will use the following paths:

                logDir: /var/tmp/embed/log/qemu
           swtpmLogDir: /var/tmp/embed/log/swtpm
         configBaseDir: /var/tmp/embed/etc/qemu
              stateDir: /var/tmp/embed/run/qemu
         swtpmStateDir: /var/tmp/embed/run/swtpm
              cacheDir: /var/tmp/embed/cache/qemu
                libDir: /var/tmp/embed/lib/qemu
       swtpmStorageDir: /var/tmp/embed/lib/swtpm
 defaultTLSx509certdir: /var/tmp/embed/etc/pki/qemu

These are identical whether the embedded driver is privileged
or unprivileged.

This compares with the system instance which uses

                logDir: /var/log/libvirt/qemu
           swtpmLogDir: /var/log/swtpm/libvirt/qemu
         configBaseDir: /etc/libvirt/qemu
              stateDir: /run/libvirt/qemu
         swtpmStateDir: /run/libvirt/qemu/swtpm
              cacheDir: /var/cache/libvirt/qemu
                libDir: /var/lib/libvirt/qemu
       swtpmStorageDir: /var/lib/libvirt/swtpm
 defaultTLSx509certdir: /etc/pki/qemu

At this time all features present in the QEMU driver are available when
running in embedded mode, availability matching whether the embedded
driver is privileged or unprivileged.

Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
2020-01-27 11:04:03 +00:00
Daniel P. Berrangé
88446e07b2 libvirt: support an "embed" URI path selector for opening drivers
The driver URI scheme:

  "$drivername:///embed?root=/some/path"

enables a new way to use the drivers by embedding them directly in the
calling process. To use this the process must have a thread running the
libvirt event loop. This URI will then cause libvirt to dynamically load
the driver module and call its global initialization function. This
syntax is applicable to any driver, but only those will have been
modified to support a custom root directory and embed URI path will
successfully open.

The application can now make normal libvirt API calls which are all
serviced in-process with no RPC layer involved.

It is required to specify an explicit root directory, and locks will be
acquired on this directory to avoid conflicting with another app that
might accidentally pick the same directory.

Use of '/' is not explicitly forbidden, but note that the file layout
used underneath the embedded driver root does not match the file
layout used by system/session mode drivers. So this cannot be used as
a backdoor to interact with, or fake, the system/session mode drivers.

Libvirt will create arbitrary files underneath this root directory. The
root directory can be kept untouched across connection open attempts if
the application needs persistence. The application is responsible for
purging everything underneath this root directory when finally no longer
required.

Even when a virt driver is used in embedded mode, it is still possible
for it to in turn use functionality that calls out to other secondary
drivers in libvirtd. For example an embedded instance of QEMU can open
the network, secret or storage drivers in the system libvirtd.

That said, the application would typically want to at least open an
embedded secret driver ("secret:///embed?root=/some/path"). Note that
multiple different embedded drivers can use the same root prefix and
co-operate just as they would inside a normal libvirtd daemon.

A key thing to note is that for this to work, the application that links
to libvirt *MUST* be built with -Wl,--export-dynamic to ensure that
symbols from libvirt.so are exported & thus available to the dynamically
loaded driver module. If libvirt.so itself was dynamically loaded then
RTLD_GLOBAL must be passed to dlopen().

Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
2020-01-27 11:03:49 +00:00