vfio/mlx5: Align the page tracking max message size with the device capability

[ Upstream commit 9c7c5430 ]

Align the page tracking maximum message size with the device's
capability instead of relying on PAGE_SIZE.

This adjustment resolves a mismatch on systems where PAGE_SIZE is 64K,
but the firmware only supports a maximum message size of 4K.

Now that we rely on the device's capability for max_message_size, we
must account for potential future increases in its value.

Key considerations include:
- Supporting message sizes that exceed a single system page (e.g., an 8K
  message on a 4K system).
- Ensuring the RQ size is adjusted to accommodate at least 4
  WQEs/messages, in line with the device specification.

The above has been addressed as part of the patch.

Fixes: 79c3cf27 ("vfio/mlx5: Init QP based resources for dirty tracking")
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Tested-by: Yingshun Cui <yicui@redhat.com>
Signed-off-by: Yishai Hadas <yishaih@nvidia.com>
Link: https://lore.kernel.org/r/20241205122654.235619-1-yishaih@nvidia.com


Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>