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Re: [Xen-devel] [PATCH v8 --for 4.6 COLO 03/25] libxc/migration: Specification update for DIRTY_BITMAP records




On 07/16/2015 01:13 AM, Andrew Cooper wrote:
On 15/07/15 10:18, Yang Hongyang wrote:
Used by secondary to send it's dirty bitmap to primary under COLO.

Signed-off-by: Yang Hongyang <yanghy@xxxxxxxxxxxxxx>
---
  docs/specs/libxc-migration-stream.pandoc | 24 +++++++++++++++++++++++-
  tools/libxc/xc_sr_common.c               |  1 +
  tools/libxc/xc_sr_stream_format.h        |  1 +
  3 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/docs/specs/libxc-migration-stream.pandoc 
b/docs/specs/libxc-migration-stream.pandoc
index 68fa513..480d357 100644
--- a/docs/specs/libxc-migration-stream.pandoc
+++ b/docs/specs/libxc-migration-stream.pandoc
@@ -227,7 +227,9 @@ type         0x00000000: END

               0x0000000E: CHECKPOINT

-             0x0000000F - 0x7FFFFFFF: Reserved for future _mandatory_
+             0x0000000F: DIRTY_BITMAP
+
+             0x00000010 - 0x7FFFFFFF: Reserved for future _mandatory_
               records.

               0x80000000 - 0xFFFFFFFF: Reserved for future _optional_
@@ -601,6 +603,26 @@ CHECKPOINT record or an END record.

  \clearpage

+DIRTY_BITMAP
+------------

I would name this DIRTY_PFN_LIST or similar, as the content of data
isn't actually a bitmap.

This sounds better, thanks!


+
+A dirty_bitmap record is used for secondary to send it's dirty bitmap
+to primary while doing a checkpoint under COLO. This record only exists
+in back channel.

This section should purely be a description of the content.  i.e.

"A DIRTY\_xxx record is used to convey information about dirty memory in
the VM.  It is an unordered list of PFNs."

Ok.


+
+     0     1     2     3     4     5     6     7 octet
+    +-------------------------------------------------+
+    | pfn[0]                                          |
+    +-------------------------------------------------+
+    ...
+    +-------------------------------------------------+
+    | pfn[C-1]                                        |
+    +-------------------------------------------------+
+
+The count of the pfn is: record->length/sizeof(uint64_t).

"The count of pfns is", although I would like to hope that this is
obvious from the diagram.

Down here, there should be more description of record circumstances,
e.g. currently only applicable in the backchannel of a checkpointed stream.

Also please put some validation logic for this in
tools/python/xen/migration/libxc.py

Will do, thank you.


~Andrew
.


--
Thanks,
Yang.

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