[PATCH v6 00/18] introduce the Xen PV Calls backend

[Stefano Stabellini]

Hi all,

this series introduces the backend for the newly introduced PV Calls
procotol.

PV Calls is a paravirtualized protocol that allows the implementation of
a set of POSIX functions in a different domain. The PV Calls frontend
sends POSIX function calls to the backend, which implements them and
returns a value to the frontend and acts on the function call.

For more information about PV Calls, please read:

https://xenbits.xen.org/docs/unstable/misc/pvcalls.html

I tried to split the source code into small pieces to make it easier to
read and understand. Please review!


Changes in v6:
- send ENOTSUPP to frontends for unsupported commands
- reset notify_all
- use a threaded irq handler instead of a workqueue to handle guest
  commands

Changes in v5:
- added review-byes
- remove unnecessary gotos
- ret 0 in pvcalls_back_connect
- do not lose ret values
- remove queue->rskq_lock
- make sure all accesses to socket_mappings and socketpass_mappings are
  protected by socket_lock
- rename ring_size to array_size

Changes in v4:
- add reviewed-bys
- fix return values of many functions
- remove pointless initializers
- print a warning if ring_order > MAX_RING_ORDER
- remove map->ioworker.cpu
- use queue_work instead of queue_work_on
- add sock_release() on error paths where appropriate
- add a comment in __pvcalls_back_accept about racing with
  pvcalls_back_accept and atomicity of reqcopy
- remove unneded (void*) casts
- remove unneded {}
- fix backend_disconnect if !mappass
- remove pointless continue in backend_disconnect
- remove pointless memset of &pvcalls_back_global
- pass *opaque to pvcalls_conn_back_read
- improve WARN_ON in pvcalls_conn_back_read
- fix error checks in pvcalls_conn_back_write
- XEN_PVCALLS_BACKEND depends on XEN_BACKEND
- rename priv to fedata across all patches

Changes in v3:
- added reviewed-bys
- return err from pvcalls_back_probe
- remove old comments
- use a xenstore transaction in pvcalls_back_probe
- ignore errors from xenbus_switch_state
- rename pvcalls_back_priv to pvcalls_fedata
- remove addr from backend_connect
- remove priv->work, add comment about theoretical race
- use IPPROTO_IP
- refactor active socket allocation in a single new function

Changes in v2:
- allocate one ioworker per socket (rather than 1 per vcpu)
- rename privs to frontends
- add newlines
- define "1" in the public header
- better error returns in pvcalls_back_probe
- do not set XenbusStateClosed twice in set_backend_state
- add more comments
- replace rw_semaphore with semaphore
- rename pvcallss to socket_lock
- move xenbus_map_ring_valloc closer to first use in backend_connect
- use more traditional return codes from pvcalls_back_handle_cmd and
  callees
- remove useless dev == NULL checks
- replace lock_sock with more appropriate and fine grained socket locks


Stefano Stabellini (18):
      xen: introduce the pvcalls interface header
      xen/pvcalls: introduce the pvcalls xenbus backend
      xen/pvcalls: initialize the module and register the xenbus backend
      xen/pvcalls: xenbus state handling
      xen/pvcalls: connect to a frontend
      xen/pvcalls: handle commands from the frontend
      xen/pvcalls: implement socket command
      xen/pvcalls: implement connect command
      xen/pvcalls: implement bind command
      xen/pvcalls: implement listen command
      xen/pvcalls: implement accept command
      xen/pvcalls: implement poll command
      xen/pvcalls: implement release command
      xen/pvcalls: disconnect and module_exit
      xen/pvcalls: implement the ioworker functions
      xen/pvcalls: implement read
      xen/pvcalls: implement write
      xen: introduce a Kconfig option to enable the pvcalls backend

 drivers/xen/Kconfig                |   12 +
 drivers/xen/Makefile               |    1 +
 drivers/xen/pvcalls-back.c         | 1238 ++++++++++++++++++++++++++++++++++++
 include/xen/interface/io/pvcalls.h |  121 ++++
 include/xen/interface/io/ring.h    |    2 +
 5 files changed, 1374 insertions(+)
 create mode 100644 drivers/xen/pvcalls-back.c
 create mode 100644 include/xen/interface/io/pvcalls.h