diff options
Diffstat (limited to 'docs/devel')
| -rw-r--r-- | docs/devel/migration/vfio.rst | 45 | ||||
| -rw-r--r-- | docs/devel/qapi-code-gen.rst | 3 | ||||
| -rw-r--r-- | docs/devel/testing/functional.rst | 8 |
3 files changed, 50 insertions, 6 deletions
diff --git a/docs/devel/migration/vfio.rst b/docs/devel/migration/vfio.rst index c49482eab6..673e354754 100644 --- a/docs/devel/migration/vfio.rst +++ b/docs/devel/migration/vfio.rst @@ -67,15 +67,35 @@ VFIO implements the device hooks for the iterative approach as follows: * A ``switchover_ack_needed`` function that checks if the VFIO device uses "switchover-ack" migration capability when this capability is enabled. -* A ``save_state`` function to save the device config space if it is present. +* A ``switchover_start`` function that in the multifd mode starts a thread that + reassembles the multifd received data and loads it in-order into the device. + In the non-multifd mode this function is a NOP. + +* A ``save_state`` function to save the device config space if it is present + in the non-multifd mode. + In the multifd mode it just emits either a dummy EOS marker. * A ``save_live_complete_precopy`` function that sets the VFIO device in _STOP_COPY state and iteratively copies the data for the VFIO device until the vendor driver indicates that no data remains. + In the multifd mode it just emits a dummy EOS marker. + +* A ``save_live_complete_precopy_thread`` function that in the multifd mode + provides thread handler performing multifd device state transfer. + It sets the VFIO device to _STOP_COPY state, iteratively reads the data + from the VFIO device and queues it for multifd transmission until the vendor + driver indicates that no data remains. + After that, it saves the device config space and queues it for multifd + transfer too. + In the non-multifd mode this thread is a NOP. * A ``load_state`` function that loads the config section and the data sections that are generated by the save functions above. +* A ``load_state_buffer`` function that loads the device state and the device + config that arrived via multifd channels. + It's used only in the multifd mode. + * ``cleanup`` functions for both save and load that perform any migration related cleanup. @@ -176,8 +196,11 @@ Live migration save path Then the VFIO device is put in _STOP_COPY state (FINISH_MIGRATE, _ACTIVE, _STOP_COPY) .save_live_complete_precopy() is called for each active device - For the VFIO device, iterate in .save_live_complete_precopy() until + For the VFIO device: in the non-multifd mode iterate in + .save_live_complete_precopy() until pending data is 0 + In the multifd mode this iteration is done in + .save_live_complete_precopy_thread() instead. | (POSTMIGRATE, _COMPLETED, _STOP_COPY) Migraton thread schedules cleanup bottom half and exits @@ -194,6 +217,9 @@ Live migration resume path (RESTORE_VM, _ACTIVE, _STOP) | For each device, .load_state() is called for that device section data + transmitted via the main migration channel. + For data transmitted via multifd channels .load_state_buffer() is called + instead. (RESTORE_VM, _ACTIVE, _RESUMING) | At the end, .load_cleanup() is called for each device and vCPUs are started @@ -206,3 +232,18 @@ Postcopy ======== Postcopy migration is currently not supported for VFIO devices. + +Multifd +======= + +Starting from QEMU version 10.0 there's a possibility to transfer VFIO device +_STOP_COPY state via multifd channels. This helps reduce downtime - especially +with multiple VFIO devices or with devices having a large migration state. +As an additional benefit, setting the VFIO device to _STOP_COPY state and +saving its config space is also parallelized (run in a separate thread) in +such migration mode. + +The multifd VFIO device state transfer is controlled by +"x-migration-multifd-transfer" VFIO device property. This property defaults to +AUTO, which means that VFIO device state transfer via multifd channels is +attempted in configurations that otherwise support it. diff --git a/docs/devel/qapi-code-gen.rst b/docs/devel/qapi-code-gen.rst index 9fa94251b0..f9cfe8721f 100644 --- a/docs/devel/qapi-code-gen.rst +++ b/docs/devel/qapi-code-gen.rst @@ -229,7 +229,8 @@ These are of the form PREFIX_NAME, where PREFIX is derived from the enumeration type's name, and NAME from the value's name. For the example above, the generator maps 'MyEnum' to MY_ENUM and 'value1' to VALUE1, resulting in the enumeration constant MY_ENUM_VALUE1. The -optional 'prefix' member overrides PREFIX. +optional 'prefix' member overrides PREFIX. This is rarely necessary, +and should be used with restraint. The generated C enumeration constants have values 0, 1, ..., N-1 (in QAPI schema order), where N is the number of values. There is an diff --git a/docs/devel/testing/functional.rst b/docs/devel/testing/functional.rst index ecc738922b..a9fa45eac1 100644 --- a/docs/devel/testing/functional.rst +++ b/docs/devel/testing/functional.rst @@ -173,7 +173,7 @@ QEMU binary selection ^^^^^^^^^^^^^^^^^^^^^ The QEMU binary used for the ``self.vm`` QEMUMachine instance will -primarily depend on the value of the ``qemu_bin`` class attribute. +primarily depend on the value of the ``qemu_bin`` instance attribute. If it is not explicitly set by the test code, its default value will be the result the QEMU_TEST_QEMU_BINARY environment variable. @@ -251,7 +251,7 @@ Many functional tests download assets (e.g. Linux kernels, initrds, firmware images, etc.) from the internet to be able to run tests with them. This imposes additional challenges to the test framework. -First there is the the problem that some people might not have an +First there is the problem that some people might not have an unconstrained internet connection, so such tests should not be run by default when running ``make check``. To accomplish this situation, the tests that download files should only be added to the "thorough" @@ -274,7 +274,9 @@ the tests are run. This pre-caching is done with the qemu_test.Asset class. To use it in your test, declare an asset in your test class with its URL and SHA256 checksum like this:: - ASSET_somename = ( + from qemu_test import Asset + + ASSET_somename = Asset( ('https://www.qemu.org/assets/images/qemu_head_200.png'), '34b74cad46ea28a2966c1d04e102510daf1fd73e6582b6b74523940d5da029dd') |