Merge remote-tracking branch 'remotes/stefanha-gitlab/tags/block-pull-request' into...

Pull request

Stefano's performance regression fix for commit 2558cb8dd4 ("linux-aio:
increasing MAX_EVENTS to a larger hardcoded value").

# gpg: Signature made Wed 21 Jul 2021 14:12:47 BST
# gpg:                using RSA key 8695A8BFD3F97CDAAC35775A9CA4ABB381AB73C8
# gpg: Good signature from "Stefan Hajnoczi <stefanha@redhat.com>" [full]
# gpg:                 aka "Stefan Hajnoczi <stefanha@gmail.com>" [full]
# Primary key fingerprint: 8695 A8BF D3F9 7CDA AC35  775A 9CA4 ABB3 81AB 73C8

* remotes/stefanha-gitlab/tags/block-pull-request:
  linux-aio: limit the batch size using `aio-max-batch` parameter
  iothread: add aio-max-batch parameter
  iothread: generalize iothread_set_param/iothread_get_param

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>