On March 4, 2025 12:57 pm, Markus Frank wrote: > Signed-off-by: Markus Frank <m.fr...@proxmox.com> > --- > v14: > * addressed formulation nits > * added paragraph about expose-acl & expose-xattr > > qm.adoc | 99 +++++++++++++++++++++++++++++++++++++++++++++++++++++++-- > 1 file changed, 97 insertions(+), 2 deletions(-) > > diff --git a/qm.adoc b/qm.adoc > index 4bb8f2c..86b3877 100644 > --- a/qm.adoc > +++ b/qm.adoc > @@ -1202,6 +1202,100 @@ 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 filesystem designed for virtual environments. It > allows to > +share a directory tree available on the host by mounting it within VMs. It > does > +not use the network stack and aims to offer similar performance and > semantics as > +the source filesystem. > + > +To use virtio-fs, the https://gitlab.com/virtio-fs/virtiofsd[virtiofsd] > daemon > +needs to run in the background. This happens automatically in {pve} when > +starting a VM using a virtio-fs mount. > + > +Linux VMs with kernel >=5.4 support virtio-fs by default. > + > +There is a guide available on how to utilize virtio-fs in Windows VMs. > +https://github.com/virtio-win/kvm-guest-drivers-windows/wiki/Virtiofs:-Shared-file-system > + > +Known Limitations > +^^^^^^^^^^^^^^^^^ > + > +* If virtiofsd crashes, its mount point will hang in the VM until the VM > +is completely stopped. > +* virtiofsd not responding may result in a hanging mount in the VM, similar > to > +an unreachable NFS. > +* Memory hotplug does not work in combination with virtio-fs (also results in > +hanging access).
should we make them mutually exclusive then? > +* Memory related features such as live migration, snapshots, and hibernate > are > +not available with virtio-fs devices. > +* Windows cannot understand ACLs in the context of virtio-fs. Therefore, do > not > +expose ACLs for Windows VMs, otherwise the virtio-fs device will not be > +visible within the VM. > + > +Add Mapping for Shared Directories > +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > + > +To add a mapping for a shared directory, you can use the API directly with > +`pvesh` as described in the xref:resource_mapping[Resource Mapping] section: > + > +---- > +pvesh create /cluster/mapping/dir --id dir1 \ > + --map node=node1,path=/path/to/share1 \ > + --map node=node2,path=/path/to/share2,announce-submounts=1 \ > +---- > + > +Set `announce-submounts` to `1` if multiple filesystems are mounted in a > shared > +directory. This tells the guest which directories are mount points to prevent > +data loss/corruption. With `announce-submounts`, virtiofsd reports a > different > +device number for each submount it encounters. Without it, duplicates may be > +created because inode IDs are only unique on a single filesystem. > + > +Add virtio-fs to a VM > +^^^^^^^^^^^^^^^^^^^^^ > + > +To share a directory using virtio-fs, add the parameter `virtiofs<N>` (N can > be > +anything between 0 and 9) to the VM config and use a directory ID (dirid) > that > +has been configured in the resource mapping. Additionally, you can set the > +`cache` option to either `always`, `never`, or `auto` (default: `auto`), > +depending on your requirements. How the different caching modes behave can be > +read at https://lwn.net/Articles/774495/ under the "Caching Modes" section. > To > +enable writeback cache set `writeback` to `1`. > + > +Virtiofsd supports ACL and xattr passthrough (can be enabled with the > +`expose-acl` and `expose-xattr` options), allowing the guest to access ACLs > and > +xattrs if the underlying host filesystem supports them, but they must also be > +compatible with the guest filesystem (for example most Linux filesystems > support > +ACLs, while Windows filesystems do not). > + > +The `expose-acl` option automatically implies `expose-xattr`, that is, it > makes > +no difference if you set `expose-xattr` to `0` if `expose-acl` is set to `1`. > + > +If you want virtio-fs to honor the `O_DIRECT` flag, you can set the > `direct-io` > +parameter to `1` (default: `0`). This will degrade performance, but is > useful if > +applications do their own caching. > + > +---- > +qm set <vmid> -virtiofs0 dirid=<dirid>,cache=always,direct-io=1 > +qm set <vmid> -virtiofs1 <dirid>,cache=never,expose-xattr=1 > +qm set <vmid> -virtiofs2 <dirid>,expose-acl=1,writeback=1 > +---- > + > +To mount virtio-fs in a guest VM with the Linux kernel virtio-fs driver, run > the > +following command inside the guest: > + > +---- > +mount -t virtiofs <mount tag> <mount point> > +---- > + > +The dirid associated with the path on the current node is also used as the > mount > +tag (name used to mount the device on the guest). > + > +For more information on available virtiofsd parameters, see the > +https://gitlab.com/virtio-fs/virtiofsd[GitLab virtiofsd project page]. > + > [[qm_bootorder]] > Device Boot Order > ~~~~~~~~~~~~~~~~~ > @@ -1885,8 +1979,9 @@ in the relevant tab in the `Resource Mappings` > category, or on the cli with > > [thumbnail="screenshot/gui-datacenter-mapping-pci-edit.png"] > > -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 > -- > 2.39.5 > > > > _______________________________________________ > pve-devel mailing list > pve-devel@lists.proxmox.com > https://lists.proxmox.com/cgi-bin/mailman/listinfo/pve-devel > > > _______________________________________________ pve-devel mailing list pve-devel@lists.proxmox.com https://lists.proxmox.com/cgi-bin/mailman/listinfo/pve-devel
