[Qemu-devel] [PATCH v3 00/28] 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.

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

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 (28):
  misc: indentation
  vhost-user: minor simplification
  vhost: don't assume opaque is a fd, use backend cleanup
  vhost: make vhost_log_put() idempotent
  vhost: call vhost_log_put() on cleanup
  vhost: add vhost device only after all success
  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: change some assert() for error_report() or silent fail
  vhost: use error_report() instead of fprintf(stderr,...)
  vhost-user: check qemu_chr_fe_set_msgfds() return value
  vhost-user: check vhost_user_{read,write}() return value
  qemu-char: check socket is actually connected
  vhost-user: keep vhost_net after a disconnection
  Revert "vhost-net: do not crash if backend is not present"
  get_vhost_net() should be != null after vhost_user_init
  vhost-net: success if backend has no ops->vhost_migration_done
  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        |  28 ++++-----
 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          |  44 ++++++++------
 qemu-char.c               |  82 ++++++++++++++++++--------
 tests/Makefile.include    |   2 +-
 tests/vhost-user-test.c   | 147 +++++++++++++++++++++++++++++++++++++++++++++-
 tests/virtio-net-test.c   |  12 +++-
 11 files changed, 385 insertions(+), 133 deletions(-)

-- 
2.9.0