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authorRajithaY <rajithax.yerrumsetty@intel.com>2017-04-25 03:31:15 -0700
committerRajitha Yerrumchetty <rajithax.yerrumsetty@intel.com>2017-05-22 06:48:08 +0000
commitbb756eebdac6fd24e8919e2c43f7d2c8c4091f59 (patch)
treeca11e03542edf2d8f631efeca5e1626d211107e3 /qemu/docs/virtio-migration.txt
parenta14b48d18a9ed03ec191cf16b162206998a895ce (diff)
Adding qemu as a submodule of KVMFORNFV
This Patch includes the changes to add qemu as a submodule to kvmfornfv repo and make use of the updated latest qemu for the execution of all testcase Change-Id: I1280af507a857675c7f81d30c95255635667bdd7 Signed-off-by:RajithaY<rajithax.yerrumsetty@intel.com>
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-Virtio devices and migration
-============================
-
-Copyright 2015 IBM Corp.
-
-This work is licensed under the terms of the GNU GPL, version 2 or later. See
-the COPYING file in the top-level directory.
-
-Saving and restoring the state of virtio devices is a bit of a twisty maze,
-for several reasons:
-- state is distributed between several parts:
- - virtio core, for common fields like features, number of queues, ...
- - virtio transport (pci, ccw, ...), for the different proxy devices and
- transport specific state (msix vectors, indicators, ...)
- - virtio device (net, blk, ...), for the different device types and their
- state (mac address, request queue, ...)
-- most fields are saved via the stream interface; subsequently, subsections
- have been added to make cross-version migration possible
-
-This file attempts to document the current procedure and point out some
-caveats.
-
-
-Save state procedure
-====================
-
-virtio core virtio transport virtio device
------------ ---------------- -------------
-
- save() function registered
- via register_savevm()
-virtio_save() <----------
- ------> save_config()
- - save proxy device
- - save transport-specific
- device fields
-- save common device
- fields
-- save common virtqueue
- fields
- ------> save_queue()
- - save transport-specific
- virtqueue fields
- ------> save_device()
- - save device-specific
- fields
-- save subsections
- - device endianness,
- if changed from
- default endianness
- - 64 bit features, if
- any high feature bit
- is set
- - virtio-1 virtqueue
- fields, if VERSION_1
- is set
-
-
-Load state procedure
-====================
-
-virtio core virtio transport virtio device
------------ ---------------- -------------
-
- load() function registered
- via register_savevm()
-virtio_load() <----------
- ------> load_config()
- - load proxy device
- - load transport-specific
- device fields
-- load common device
- fields
-- load common virtqueue
- fields
- ------> load_queue()
- - load transport-specific
- virtqueue fields
-- notify guest
- ------> load_device()
- - load device-specific
- fields
-- load subsections
- - device endianness
- - 64 bit features
- - virtio-1 virtqueue
- fields
-- sanitize endianness
-- sanitize features
-- virtqueue index sanity
- check
- - feature-dependent setup
-
-
-Implications of this setup
-==========================
-
-Devices need to be careful in their state processing during load: The
-load_device() procedure is invoked by the core before subsections have
-been loaded. Any code that depends on information transmitted in subsections
-therefore has to be invoked in the device's load() function _after_
-virtio_load() returned (like e.g. code depending on features).
-
-Any extension of the state being migrated should be done in subsections
-added to the core for compatibility reasons. If transport or device specific
-state is added, core needs to invoke a callback from the new subsection.