[pve-devel] [PATCH docs v6 1/1] added shared filesystem doc for virtio-fs

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

Signed-off-by: Markus Frank <m.frank@proxmox.com>
---
 qm.adoc | 60 +++++++++++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 58 insertions(+), 2 deletions(-)

diff --git a/qm.adoc b/qm.adoc
index e35dbf0..00a0668 100644
--- a/qm.adoc
+++ b/qm.adoc
@@ -997,6 +997,61 @@ recommended to always use a limiter to avoid guests using too many host
 resources. If desired, a value of '0' for `max_bytes` can be used to disable
 all limits.
 
+[[qm_virtiofs]]
+Virtio-fs
+~~~~~~~~~
+
+Virtio-fs is a shared file system, that enables sharing a directory between
+host and guest VM while taking advantage of the locality of virtual machines
+and the hypervisor to get a higher throughput than 9p.
+The parameter `hugepages` must be disabled to use virtio-fs.
+
+Add mapping for Shared Directories
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+To add a mapping, go to the Resource Mapping tab in Datacenter in the WebUI,
+use the API directly with pvesh as described in the
+xref:resource_mapping[Resource Mapping] section,
+or add the mapping to the configuration file /etc/pve/mapping/dir.cfg:
+
+----
+some-dir-id
+	map node=node1,path=/share/,xattr=1,acl=1,submounts=1
+	map node=node2,path=/share/,xattr=1
+	map node=node3,path=/different-share-path/,submounts=1
+	map node=node4,path=/foobar/
+	map node=node5,path=/somewhere/,acl=1
+----
+
+The Parameter `acl` automatically implies `xattr`, so there would be no need to
+set `xattr` for node1 in this example.
+Set `submounts` to `1` when using multiple file systems in the shared directory.
+
+Add virtiofs to VM
+^^^^^^^^^^^^^^^^^^
+
+To share a directory with virtio-fs, you need to specify the directory ID
+that has been configured in the Resource Mapping. Additionally, you can set
+the `cache` option to either `always`, `never`, or `auto`, depending on your
+requirements. If you want virtio-fs to honor the `O_DIRECT` flag, you can set the
+`direct-io` parameter to `1`.
+
+----
+qm set <vmid> -virtiofs0 dirid=<dirid>,tag=<mount tag>,cache=always,direct-io=1
+qm set <vmid> -virtiofs1 <dirid>,tag=<mount tag>,cache=never
+qm set <vmid> -virtiofs2 <dirid>,tag=<mount tag>
+----
+
+To mount virtio-fs in a guest VM with the Linux kernel virtiofs driver, run the
+following command:
+
+----
+mount -t virtiofs <mount tag> <mount point>
+----
+
+For more information on the virtiofsd parameters, see:
+https://gitlab.com/virtio-fs/virtiofsd[GitLab virtiofsd]
+
 [[qm_bootorder]]
 Device Boot Order
 ~~~~~~~~~~~~~~~~~
@@ -1600,8 +1655,9 @@ in the relevant tab in the `Resource Mappings` category, or on the cli with
 # pvesh create /cluster/mapping/<type> <options>
 ----
 
-Where `<type>` is the hardware type (currently either `pci` or `usb`) and
-`<options>` are the device mappings and other configuration parameters.
+Where `<type>` is the hardware type (currently either `pci`, `usb` or
+xref:qm_virtiofs[dir]) and `<options>` are the device mappings and other
+configuration parameters.
 
 Note that the options must include a map property with all identifying
 properties of that hardware, so that it's possible to verify the hardware did
-- 
2.39.2