[PATCH v3 0/4] vhost-vsock: force virtio version 1

[Stefano Garzarella <sgarzare@redhat.com>]

v3:
   - Added patch 1 (v2: [1]) since it is a prerequisite for other patches
   - Patch 1:
     - added virtio_legacy_check_disabled() helper
     - moved warning where error was returned [Cornelia]
   - Patches 2 & 4:
     - forced virtio version 1 only with new machine types
     - removed Cornelia's R-b since I changed these patches

v2: https://lists.gnu.org/archive/html/qemu-devel/2020-08/msg04437.html
v1: https://lists.gnu.org/archive/html/qemu-devel/2020-08/msg04373.html

Recently changes in QEMU 5.1 requires to set 'disable-legacy=on'
on vhost-vsock-pci and vhost-user-vsock-pci devices:

    $ ./qemu-system-x86_64 ... -device vhost-vsock-pci,guest-cid=5
        qemu-system-x86_64: -device vhost-vsock-pci,guest-cid=5:
        device is modern-only, use disable-legacy=on

As discussed with Cornelia [2], this series forces virtio version 1
to vhost-vsock-pci, vhost-user-vsock-pci, and vhost-vsock-ccw devices.

virtio-vsock was introduced after the release of VIRTIO 1.0 specifications,
so it should be 'modern-only'.
In addition Cornelia verified that forcing a legacy mode on vhost-vsock-pci
device using x86-64 host and s390x guest, so with different endianness,
produces strange behaviours.

This series should be merged in stable branch since it fixes migration issues
with QEMU 5.1:
- we skip legacy support check in the old machine types (< 5.1)
- we force virtio version 1 for vhost-vsock-pci and vhost-vsock-ccw devices
  only in the new machine types (>= 5.1). vhost-user-vsock-pci was introduced
  in 5.1 and doesn't support migration, so we forced virtio version 1 in any
  case,

Thanks,
Stefano

[1] https://lists.gnu.org/archive/html/qemu-devel/2020-09/msg05312.html
[2] https://lists.gnu.org/archive/html/qemu-devel/2020-08/msg02515.html

Stefano Garzarella (4):
  virtio: skip legacy support check on machine types less than 5.1
  vhost-vsock-pci: force virtio version 1
  vhost-user-vsock-pci: force virtio version 1
  vhost-vsock-ccw: force virtio version 1

 include/hw/virtio/virtio.h       |  2 ++
 hw/core/machine.c                |  1 +
 hw/s390x/vhost-vsock-ccw.c       | 12 ++++++++++++
 hw/s390x/virtio-ccw.c            | 15 ++++++++++++---
 hw/virtio/vhost-user-vsock-pci.c |  2 +-
 hw/virtio/vhost-vsock-pci.c      | 10 +++++++++-
 hw/virtio/virtio-pci.c           | 14 ++++++++++++--
 hw/virtio/virtio.c               |  7 +++++++
 8 files changed, 56 insertions(+), 7 deletions(-)

-- 
2.26.2