At the end of live migration, QEMU uses msync() to flush the data to
the backend storage. When the backend file is a character device dax,
the pages explicitly avoid the page cache. It will return failure from msync().
The following warning is output.
"warning: qemu_ram_msync: failed to sync memory range“
So we add 'pmem=on' to avoid calling msync(), use the QEMU command line:
-object memory-backend-file,id=mem1,pmem=on,mem-path=/dev/dax0.0,size=4G
Reviewed-by: Stefan Hajnoczi <stefa...@redhat.com>
Reviewed-by: Pankaj Gupta <pankaj.gupta.li...@gmail.com>
Signed-off-by: Jingqi Liu <jingqi....@intel.com>
---
docs/nvdimm.txt | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/docs/nvdimm.txt b/docs/nvdimm.txt
index c2c6e441b3..31048aff5e 100644
--- a/docs/nvdimm.txt
+++ b/docs/nvdimm.txt
@@ -243,6 +243,13 @@ use the QEMU command line:
-object memory-backend-file,id=nv_mem,mem-path=/XXX/yyy,size=4G,pmem=on
+At the end of live migration, QEMU uses msync() to flush the data to the
+backend storage. When the backend file is a character device dax, the pages
+explicitly avoid the page cache. It will return failure from msync().
+So we add 'pmem=on' to avoid calling msync(), use the QEMU command line:
+
+ -object memory-backend-file,id=mem1,pmem=on,mem-path=/dev/dax0.0,size=4G
+
References
----------
--
2.17.1
