[PATCH docs v2 8/11] virtiofs: add documentation for live migration

[Markus Frank <m.frank@proxmox.com>]

Also update the virtiofs known limitations.

Signed-off-by: Markus Frank <m.frank@proxmox.com>
---
v2 changes:
* added link for further information about virtiofs limitations.

 qm.adoc | 31 ++++++++++++++++++++++++++++++-
 1 file changed, 30 insertions(+), 1 deletion(-)

diff --git a/qm.adoc b/qm.adoc
index 09fbd20..03224a7 100644
--- a/qm.adoc
+++ b/qm.adoc
@@ -1297,10 +1297,12 @@ Known Limitations
 * Memory hotplug does not work in combination with virtiofs (also results in
   hanging access).
 * Memory related features such as live migration, snapshots, and hibernate are
-  not available with virtiofs devices.
+  not available with virtiofs devices on {pve} 8.
 * Windows cannot understand ACLs in the context of virtiofs. Therefore, do not
   expose ACLs for Windows VMs, otherwise the virtiofs device will not be visible
   within the VM.
+* For further limitations, see the
+  https://gitlab.com/virtio-fs/virtiofsd#limitations[GitLab page of virtiofsd].
 
 Add Mapping for Shared Directories
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -1314,6 +1316,29 @@ pvesh create /cluster/mapping/dir --id dir1 \
     --map node=node2,path=/path/to/share2 \
 ----
 
+Live Migration
+^^^^^^^^^^^^^^
+
+Live migration is possible on {pve} 9 (Debian Trixie) because versions of
+Virtiofsd starting with v1.11.0 support live migration. To enable live
+migration, select a method using the `live-migration-method` parameter in the
+Directory Mapping (xref:resource_mapping[Resource Mapping]). If a live migration
+method is selected, virtiofsd will start with the flags to enable live migration
+using the chosen method. Ensure you are using the same shared directory on both
+hosts before migrating.
+
+Available migration methods are `file-handles` and `find-path`:
+
+* In the `find-paths` migration mode, virtiofsd tries to find the path inside of
+  the shared directory for every filesystem object that must be transferred to
+  the destination.
+* In the `file-handles` migration mode every filesystem object is converted to a
+  file handle.
+
+For more information about the live migration methods, see the
+https://gitlab.com/virtio-fs/virtiofsd/-/blob/main/doc/migration.md[virtiofsd
+migration page on GitLab].
+
 Add virtiofs to a VM
 ^^^^^^^^^^^^^^^^^^^^
 
@@ -2162,6 +2187,10 @@ Currently there are the following options:
   migrating passed through devices is an experimental feature and may not work
   or cause issues.
 
+* `live-migration-method` (Directory): This sets the live migration mode for
+  virtiofs. If a live migration method is selected, virtiofsd will start with
+  the flags to enable live migration using the chosen method. Available
+  migration methods are `file-handles` and `find-path`.
 
 Managing Virtual Machines with `qm`
 ------------------------------------
-- 
2.47.3