On Mon, 10 Dec 2018 17:31:44 +0000 "Dr. David Alan Gilbert (git)" <dgilb...@redhat.com> wrote:
> From: "Dr. David Alan Gilbert" <dgilb...@redhat.com> > > Hi, > This is the first RFC for the QEMU side of 'virtio-fs'; > a new mechanism for mounting host directories into the guest > in a fast, consistent and secure manner. Our primary use > case is kata containers, but it should be usable in other scenarios > as well. > > There are corresponding patches being posted to Linux kernel, > libfuse and kata lists. > > For a fuller design description, and benchmark numbers, please see > Vivek's posting of the kernel set here: > > https://marc.info/?l=linux-kernel&m=154446243024251&w=2 > > We've got a small website with instructions on how to use it, here: > > https://virtio-fs.gitlab.io/ > > and all the code is available on gitlab at: > > https://gitlab.com/virtio-fs > Hi ! This looks like a very promising replacement for virtio-9p, at least with better chances of reaching a production quality level. Not sure I'll have enough time to step in, but please Cc me on future posts. As virtio-9p maintainer, I'll be happy to help if I can. Also I'll be happy to get rid of the fsdev proxy backend at some point (which I already wanted to replace with a vhost user based solution :-) ). Cheers, -- Greg > QEMU's changes > -------------- > > The QEMU changes are pretty small; > > There's a new vhost-user device, which is used to carry a stream of > FUSE messages to an external daemon that actually performs > all the file IO. The FUSE daemon is an external process in order to > achieve better isolation for security and resource control (e.g. number > of file descriptors) and also because it's cleaner than trying to > integrate libfuse into QEMU. > > This device has an extra BAR that contains (up to) 3 regions: > > a) a DAX mapping range ('the cache') - into which QEMU mmap's > files on behalf of the external daemon; those files are > then directly mapped by the guest in a way similar to a DAX > backed file system; one advantage of this is that multiple > guests all accessing the same files should all be sharing > those pages of host cache. > > b) An experimental set of mappings for use by a metadata versioning > daemon; this mapping is shared between multiple guests and > the daemon, but only contains a set of version counters that > allow a guest to quickly tell if its metadata is stale. > > TODO > ---- > > This is the first RFC, we know we have a bunch of things to clear up: > > a) The virtio device specificiation is still in flux and is expected > to change > > b) We'd like to find ways of reducing the map/unmap latency for DAX > > c) The metadata versioning scheme needs to settle out. > > d) mmap'ing host files has some interesting side effects; for example > if the file gets truncated by the host and then the guest accesses > the mapping, KVM can fail the guest hard. > > Dr. David Alan Gilbert (6): > virtio: Add shared memory capability > virtio-fs: Add cache BAR > virtio-fs: Add vhost-user slave commands for mapping > virtio-fs: Fill in slave commands for mapping > virtio-fs: Allow mapping of meta data version table > virtio-fs: Allow mapping of journal > > Stefan Hajnoczi (1): > virtio: add vhost-user-fs-pci device > > configure | 10 + > contrib/libvhost-user/libvhost-user.h | 3 + > docs/interop/vhost-user.txt | 35 ++ > hw/virtio/Makefile.objs | 1 + > hw/virtio/vhost-user-fs.c | 517 ++++++++++++++++++++ > hw/virtio/vhost-user.c | 16 + > hw/virtio/virtio-pci.c | 115 +++++ > hw/virtio/virtio-pci.h | 19 + > include/hw/pci/pci.h | 1 + > include/hw/virtio/vhost-user-fs.h | 79 +++ > include/standard-headers/linux/virtio_fs.h | 48 ++ > include/standard-headers/linux/virtio_ids.h | 1 + > include/standard-headers/linux/virtio_pci.h | 9 + > 13 files changed, 854 insertions(+) > create mode 100644 hw/virtio/vhost-user-fs.c > create mode 100644 include/hw/virtio/vhost-user-fs.h > create mode 100644 include/standard-headers/linux/virtio_fs.h >
