Hi, As discussed on the previous version of the virtio-fs migration series (https://lists.nongnu.org/archive/html/qemu-devel/2023-04/msg01575.html), we currently don’t have a good way to have a vhost-user back-end fully cease all operations, including background operations. To work around this, we reset it, which is not an option for stateful devices like virtio-fs.
Instead, we want the same SUSPEND/RESUME model that vhost-vdpa already has, so that we can suspend back-ends when we want them to stop doing anything (i.e. on VM stop), and resume them later (i.e. on VM resume). This series adds these vhost-user operations to the protocol and implements them in qemu. Furthermore, it has vhost-user and vhost-vdpa do roughly the same thing in their reset paths, as far as possible. That path will still remain as a fall-back if SUSPEND/RESUME is not implemented, and, given that qemu’s vhost-vdpa code currently does not make use of RESUME, it is actually always used for vhost-vdpa (to take the device out of a suspended state). Hanna Czenczek (6): vhost-user.rst: Add suspend/resume vhost-vdpa: Move vhost_vdpa_reset_status() up vhost: Do not reset suspended devices on stop vhost-user: Implement suspend/resume vhost-vdpa: Match vhost-user's status reset vhost-user: Have reset_status fall back to reset docs/interop/vhost-user.rst | 35 +++++++++++- include/hw/virtio/vhost-vdpa.h | 2 - include/hw/virtio/vhost.h | 8 +++ hw/virtio/vhost-user.c | 101 ++++++++++++++++++++++++++++++++- hw/virtio/vhost-vdpa.c | 41 ++++++------- hw/virtio/vhost.c | 8 ++- 6 files changed, 169 insertions(+), 26 deletions(-) -- 2.41.0
