[PATCH vhost 0/7] vdpa/mlx5: Parallelize device suspend/resume

[Dragos Tatulea <dtatulea@nvidia.com>]

This series parallelizes the mlx5_vdpa device suspend and resume
operations through the firmware async API. The purpose is to reduce live
migration downtime.

The series starts with changing the VQ suspend and resume commands
to the async API. After that, the switch is made to issue multiple
commands of the same type in parallel.

Finally, a bonus improvement is thrown in: keep the notifierd enabled
during suspend but make it a NOP. Upon resume make sure that the link
state is forwarded. This shaves around 30ms per device constant time.

For 1 vDPA device x 32 VQs (16 VQPs), on a large VM (256 GB RAM, 32 CPUs
x 2 threads per core), the improvements are:

+-------------------+--------+--------+-----------+
| operation         | Before | After  | Reduction |
|-------------------+--------+--------+-----------|
| mlx5_vdpa_suspend | 37 ms  | 2.5 ms |     14x   |
| mlx5_vdpa_resume  | 16 ms  | 5 ms   |      3x   |
+-------------------+--------+--------+-----------+

Note for the maintainers:
The first patch contains changes for mlx5_core. This must be applied
into the mlx5-vhost tree [0] first. Once this patch is applied on
mlx5-vhost, the change has to be pulled from mlx5-vdpa into the vhost
tree and only then the remaining patches can be applied.

[0] https://git.kernel.org/pub/scm/linux/kernel/git/mellanox/linux.git/log/?h=mlx5-vhost

Dragos Tatulea (7):
  net/mlx5: Support throttled commands from async API
  vdpa/mlx5: Introduce error logging function
  vdpa/mlx5: Use async API for vq query command
  vdpa/mlx5: Use async API for vq modify commands
  vdpa/mlx5: Parallelize device suspend
  vdpa/mlx5: Parallelize device resume
  vdpa/mlx5: Keep notifiers during suspend but ignore

 drivers/net/ethernet/mellanox/mlx5/core/cmd.c |  21 +-
 drivers/vdpa/mlx5/core/mlx5_vdpa.h            |   7 +
 drivers/vdpa/mlx5/net/mlx5_vnet.c             | 435 +++++++++++++-----
 3 files changed, 333 insertions(+), 130 deletions(-)

-- 
2.45.2