On 08/25/2015 04:40 AM, Andrew Cooper wrote:
Signed-off-by: Andrew Cooper <andrew.coop...@citrix.com>
---
v2:
* %Revision and #History, following template review
* Grammar fixes
---
docs/features/migration.pandoc | 100 ++++++++++++++++++++++++++++++++++++++++
1 file changed, 100 insertions(+)
create mode 100644 docs/features/migration.pandoc
diff --git a/docs/features/migration.pandoc b/docs/features/migration.pandoc
new file mode 100644
index 0000000..0fd227f
--- /dev/null
+++ b/docs/features/migration.pandoc
@@ -0,0 +1,100 @@
+% Migration
+% Revision 1
+
+\clearpage
+
+# Basics
+--------------- -------------
+ Status: **Supported**
+
+ Architecture: x86
+
+ Component: Toolstack
+--------------- -------------
+
+# Overview
+
+Migration is a mechanism to move a virtual machine while the VM is
+running. Live migration moves a running virtual machine between two
+physical servers, but the same mechanism can be used for non-live
+migrate (pause and copy) and suspend/resume from disk.
s/migrate/migration/ ?
+
+# User details
+
+No hardware requirements, although hypervisor logdirty support is
+required for live migration.
+
+From the command line, `xl migrate/save/restore` are the top level
+interactions. e.g.
+
+ xl create my-vm.cfg
+ xl migrate my-vm localhost
+
+or
+
+ xl create my-vm.cfg
+ xl save my-vm /path/to/save/file
+ xl restore /path/to/save/file
+
+Xen 4.6 sees the instruction of Migration v2. There is no change for
Xen 4.6 sees the introduction of Migration v2.
Or, Xen 4.6 introduces Migration v2.
+people using `xl`, although the `libxl` API has had an extension.
+
+# Technical details
+
+Migration is formed of several layers. `libxc` is responsible for the
+contents of the VM (ram, vcpus, etc) and the live migration loop, while
+`libxl` is responsible for items such as emulator state.
+
+The format of the migration v2 stream is specified in two documents, and
+is architecture neutral. Compatibility with legacy streams is
+maintained via the `convert-legacy-stream` script which transforms a
+legacy stream into a migration v2 stream.
+
+* Documents
+ * `docs/specs/libxc-migration-stream.pandoc`
+ * `docs/specs/libxl-migration-stream.pandoc`
+* `libxc`
+ * `tools/libxc/xc_sr_*.[hc]`
+* `libxl`
+ * `tools/libxl/libxl_stream_{read,write}.c`
+* Scripts
+ * `tools/python/xen/migration/*.py`
+ * `tools/python/scripts/convert-legacy-stream`
+ * `tools/python/scripts/verify-stream-v2`
+
+Users of the `libxl` API have a new parameter `stream_version` in
+`domain_restore_params` which is used to distinguish between legacy and
+v2 migration streams, and hence whether legacy conversion is required.
A question better asked when you posted the patches, but is there a way to
detect if the receiver is V2 capable? I suspect sending a V2 stream to a
receiver capable only of V1 is not advised :-).
Also, commit id introducing the change would be helpful info. Looks like
3a9ace01 in this case.
+
+# Limitations
+
+Hypervisor logdirty support is incompatible with hardware passthrough,
+as IOMMU faults cannot be used to track writes.
+
+While not a bug in migration specifically, VMs are very sensitive to
+changes in cpuid information, and cpuid levelling support currently has
+its issues. Extreme care should be taken when migrating VMs between
+non-identical CPUs until the cpuid levelling improvements are complete.
+
+# Areas for improvement
+
+* Arm support
+* Linear P2M support for x86 PV
+* Live looping parameters
* cpuid levelling
Regards,
Jim
+
+# Known issues
+
+* x86 HVM guest physmap operations (not reflected in logdirty bitmap)
+* x86 HVM with PoD pages (attempts to map cause PoD allocations)
+* x86 HVM with nested-virt (no relevant information included in the
+ stream)
+* x86 PV ballooning (P2M marked dirty, target frame not marked)
+* x86 PV P2M structure changes (not noticed, stale mappings used)
+
+# History
+
+------------------------------------------------------------------------
+Date Revision Version Notes
+---------- -------- -------- -------------------------------------------
+2015-10-24 1 Xen 4.6 Document written
+---------- -------- -------- -------------------------------------------
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xen.org
http://lists.xen.org/xen-devel
