Re: [libvirt PATCHv3 04/12] docs: add virtiofs kbase

Add a document describing the usage of virtiofs. --- docs/kbase.html.in | 3 + docs/kbase/virtiofs.rst | 152 ++++++++++++++++++++++++++++++++++++++++ 2 files changed, 155 insertions(+) create mode 100644 docs/kbase/virtiofs.rst diff --git a/docs/kbase.html.in b/docs/kbase.html.in index c156414c41..7d6caf3cb1 100644 --- a/docs/kbase.html.in +++ b/docs/kbase.html.in @@ -29,6 +29,9 @@ <dt><a href="kbase/backing_chains.html">Backing chain management</a></dt> <dd>Explanation of how disk backing chain specification impacts libvirt's behaviour and basic troubleshooting steps of disk problems.</dd> + + <dt><a href="kbase/virtiofs.html">Virtio-FS</a></dt> + <dd>Share a filesystem between the guest and the host</dd> </dl> </div> diff --git a/docs/kbase/virtiofs.rst b/docs/kbase/virtiofs.rst new file mode 100644 index 0000000000..e76ff8ca4b --- /dev/null +++ b/docs/kbase/virtiofs.rst @@ -0,0 +1,152 @@ +============================ +Sharing files with Virtio-FS +============================ + +=== 8< delete before merging 8< === +NOTE: if you're looking at this note, this is just a proposal. +See the up-to-date version on: https://libvirt.org/kbase/virtiofs.html +=== 8< --------------------- 8< ===

+ +.. contents:: + +========= +Virtio-FS +========= + +Virtio-FS is a shared file system that lets virtual machines access +a directory tree on the host. Unlike existing approaches, it +is designed to offer local file system semantics and performance. + +See https://virtio-fs.gitlab.io/ + +========== +Host setup +========== + +The host-side virtiofsd daemon, like other vhost-user backed devices, +requres shared memory between the host and the guest. As of QEMU 4.2, this

+requires specifying a NUMA topology for the guest and explicitly specifying +a memory backend. Multiple options are available: + +Either of the following: + +\a) Use file-backed memory

+ +Configure the directory where the files backing the memory will be stored +with the ``memory_backing_dir`` option in ``/etc/libvirt/qemu.conf`` + +:: + + # This directory is used for memoryBacking source if configured as file. + # NOTE: big files will be stored here + memory_backing_dir = "/dev/shm/" + +\b) Use hugepage-backed memory + +Make sure there are enough huge pages allocated for the requested guest memory. +For example, for one guest with 2 GiB of RAM backed by 2 MiB hugepages: + +:: + + # virsh allocpages 2M 1024