Merge remote-tracking branch 'remotes/dgilbert/tags/pull-migration-20200925a' into staging

Migration and virtiofsd pull

Chuan Zheng's Dirtyrate and TLS changes, with small fixes from Dov and
Luarent.
Small virtiofs changes from Harry, Stefan, Vivek and Jiachen.
One HMP/monitor rework from me.

# gpg: Signature made Fri 25 Sep 2020 13:03:50 BST
# gpg:                using RSA key 45F5C71B4A0CB7FB977A9FA90516331EBC5BFDE7
# gpg: Good signature from "Dr. David Alan Gilbert (RH2) <dgilbert@redhat.com>" [full]
# Primary key fingerprint: 45F5 C71B 4A0C B7FB 977A  9FA9 0516 331E BC5B FDE7

* remotes/dgilbert/tags/pull-migration-20200925a: (26 commits)
  virtiofsd: Add -o allow_direct_io|no_allow_direct_io options
  virtiofsd: Used glib "shared" thread pool
  virtiofsd: document cache=auto default
  monitor: Use LOCK_GUARD macros
  migration/tls: add trace points for multifd-tls
  migration/tls: add support for multifd tls-handshake
  migration/tls: extract cleanup function for common-use
  migration/tls: add tls_hostname into MultiFDSendParams
  migration/tls: extract migration_tls_client_create for common-use
  migration/tls: save hostname into MigrationState
  migration: increase max-bandwidth to 128 MiB/s (1 Gib/s)
  migration: Truncate state file in xen-save-devices-state
  migration/dirtyrate: Add trace_calls to make it easier to debug
  migration/dirtyrate: Implement qmp_cal_dirty_rate()/qmp_get_dirty_rate() function
  migration/dirtyrate: Implement calculate_dirtyrate() function
  migration/dirtyrate: Implement set_sample_page_period() and is_sample_period_valid()
  migration/dirtyrate: skip sampling ramblock with size below MIN_RAMBLOCK_SIZE
  migration/dirtyrate: Compare page hash results for recorded sampled page
  migration/dirtyrate: Record hash results for each sampled page
  migration/dirtyrate: move RAMBLOCK_FOREACH_MIGRATABLE into ram.h
  ...

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