[PATCH 0/2] Enable virtio-fs on s390x

[Marc Hartmayer <mhartmay@linux.ibm.com>]

This patch series is about enabling virtio-fs on s390x. For that we need
 + some shim code (first patch), and we need
 + libvhost-user to deal with virtio endiannes for non-legacy virtio
   devices as mandated by the spec.

How to use?

For general instructions how to use virtio-fs (on x86) please have a
look at https://virtio-fs.gitlab.io/howto-qemu.html. Most of the
instructions can also be applied on s390x.

In short:

1. Install self-compiled QEMU with this patch series applied
2. Prepare host and guest kernel so they support virtio-fs

Start virtiofsd on the host

 $ virtiofsd -f --socket-path=/tmp/vhostqemu -o source=/tmp/shared

Now you can start QEMU in a separate shell on the host:

 $ qemu-system-s390x -machine type=s390-ccw-virtio,accel=kvm,memory-backend=mem \
   -object memory-backend-file,id=mem,size=2G,mem-path=/dev/shm/virtiofs,share=on,prealloc=on,prealloc-threads=1 \
   -chardev socket,id=char0,path=/tmp/vhostqemu -device vhost-user-fs-ccw,queue-size=1024,chardev=char0,tag=myfs \
   -drive if=virtio,file=disk.qcow2 \
   -m 2G -smp 2 -nographic

Log into the guest and mount it

 $ mount -t virtiofs myfs /mnt

Changelog:
 RFC v2 -> v1:
 - patch 1:
  + Added `force_revision_1 = true` (Conny)
  + I didn't add the r-b from Stefan Hajnoczi as I've added the
    changes suggested by Conny
 - squashed patches 2 and 3:
  + removed assertion in performance critical code path (Stefan)
  + dropped all dead code (Stefan)
  + removed libvhost-access.h
  
 RFC v1 -> RFC v2:
  + rebased
  + drop patch "libvhost-user: print invalid address on vu_panic" as it's not related to this series
  + drop patch "[RFC 4/4] HACK: Hard-code the libvhost-user.o-cflags for s390x"
  + patch "virtio: add vhost-user-fs-ccw device": replace qdev_set_parent_bus and object_property_set_bool by qdev_realize
  + patch "libvhost-user: handle endianness as mandated by the spec":
    Drop support for legacy virtio devices
  + add patch to fence legacy virtio devices
*** BLURB HERE ***

Halil Pasic (1):
  virtio: add vhost-user-fs-ccw device

Marc Hartmayer (1):
  libvhost-user: handle endianness as mandated by the spec

 contrib/libvhost-user/libvhost-user.c | 77 +++++++++++++++------------
 hw/s390x/Makefile.objs                |  1 +
 hw/s390x/vhost-user-fs-ccw.c          | 75 ++++++++++++++++++++++++++
 3 files changed, 119 insertions(+), 34 deletions(-)
 create mode 100644 hw/s390x/vhost-user-fs-ccw.c

-- 
2.25.4