[Qemu-devel] [PATCH v4 00/29] vhost-user reconnect fixes

[marcandre . lureau]

From: Marc-André Lureau <address@hidden>

Hi,

Since 'vhost-user: simple reconnection support' was merged, it is
possible to disconnect and reconnect a vhost-user backend. However,
many code paths in qemu may trigger assert() when the backend is
disconnected.

Some assert() could simply be replaced by error_report() or silently
fail since they are recoverable cases. Some missing error checks can
also help prevent later issues. In many cases, the code assumes
get_vhost_net() will be non-NULL after a succesful connection, so I
changed it to stay after a disconnect until the new connection comes
(as suggested by Michael). There are also code paths that are wrong,
see "don't assume opaque is a fd" patch for an example.

Since there is feature checks on reconnection, qemu should wait for
the initial connection feature negotiation to complete. The test added
demonstrates this. Additionally, a regression was found during v2,
which could have been spotted with a multiqueue test, so add a basic
one that would have exhibited the issue.

For convenience, the series is also available on:
https://github.com/elmarco/qemu, branch vhost-user-reconnect

v4:
- change notify_migration_done() patch to be VHOST_BACKEND_TYPE_USER
  specific, to avoid having to handle the case where the backend
  doesn't implement the callback
- change vhost_dev_cleanup() to assert on empty log, instead of
  adding a call to vhost_log_put()
- made "keep vhost_net after a disconnection" more robust, got rid of
  the acked_features field
- improve commit log, and some patch reorganization for clarity

v3:
- add vhost-user multiqueue test, which would have helped to find the
  following fix
- fix waiting on vhost-user connection with multiqueue (found by
  Yuanhan Liu)
- merge vhost_user_{read,write}() error checking patches
- add error reporting to vhost_user_read() (similar to
  vhost_user_write())
- add a vhost_net_set_backend() wrapper to help with potential crash
- some leak fixes

v2:
- some patch ordering: minor fix, close(fd) fix,
  assert/fprintf->error_report, check and return error,
  vhost_dev_cleanup() fixes, keep vhost_net after a disconnect, wait
  until connection is ready
- merge read/write error checks
- do not rely on link state to check vhost-user init completed

Marc-André Lureau (29):
  misc: indentation
  vhost-user: minor simplification
  vhost: don't assume opaque is a fd, use backend cleanup
  vhost: make vhost_log_put() idempotent
  vhost: assert the log was cleaned up
  vhost: fix cleanup on not fully initialized device
  vhost: make vhost_dev_cleanup() idempotent
  vhost-net: always call vhost_dev_cleanup() on failure
  vhost: fix calling vhost_dev_cleanup() after vhost_dev_init()
  vhost: do not assert() on vhost_ops failure
  vhost: use error_report() instead of fprintf(stderr,...)
  qemu-char: fix qemu_chr_fe_set_msgfds() crash when disconnected
  vhost-user: call set_msgfds unconditionally
  vhost-user: check qemu_chr_fe_set_msgfds() return value
  vhost-user: check vhost_user_{read,write}() return value
  vhost-user: keep vhost_net after a disconnection
  vhost-user: add get_vhost_net() assertions
  Revert "vhost-net: do not crash if backend is not present"
  vhost-net: vhost_migration_done is vhost-user specific
  vhost: add assert() to check runtime behaviour
  char: add chr_wait_connected callback
  char: add and use tcp_chr_wait_connected
  vhost-user: wait until backend init is completed
  tests: plug some leaks in virtio-net-test
  tests: fix vhost-user-test leak
  tests: add /vhost-user/connect-fail test
  tests: add a simple /vhost-user/multiqueue test
  vhost-user: add error report in vhost_user_write()
  vhost: add vhost_net_set_backend()

 hw/net/vhost_net.c        |  34 ++++-------
 hw/virtio/vhost-user.c    |  67 ++++++++++++++-------
 hw/virtio/vhost.c         | 123 +++++++++++++++++++++++---------------
 include/hw/virtio/vhost.h |   4 ++
 include/sysemu/char.h     |   8 +++
 net/tap.c                 |   1 +
 net/vhost-user.c          |  60 +++++++++++--------
 qemu-char.c               |  82 ++++++++++++++++++--------
 tests/Makefile.include    |   2 +-
 tests/vhost-user-test.c   | 147 +++++++++++++++++++++++++++++++++++++++++++++-
 tests/virtio-net-test.c   |  12 +++-
 11 files changed, 396 insertions(+), 144 deletions(-)

-- 
2.9.0