[PATCHv6 00/11] Xen: FIFO-based event channel ABI

[David Vrabel <david.vrabel@citrix.com>]

This is a complete implementation of the hypervisor and xl toolstack
parts of the FIFO-based event channel ABI described in this design
document:

  http://xenbits.xen.org/people/dvrabel/event-channels-F.pdf

The v6 version of the Linux patch series will be posted shortly and
can be found in the orochi-v6 branch of:

  git://xenbits.xen.org/people/dvrabel/linux.git

Patch 1-4 do some preparatory work for supporting alternate ABIs.

Patch 5 expands the number of evtchn objects a domain may have by
changing how they are allocated.

Patch 6 adds the public ABI.

Patch 7 adds the EVTCHNOP_set_priority implementation.  This will
return -ENOSYS for ABIs that do not support priority.

Patch 8* adds the FIFO-based ABI implementation.

Patch 9-10 adds the DOMCTL_set_max_evtchn implementation and adds a
function to libxc. This will also work with the 2-level ABI.

Patch 11 add the max_event_channels configuration option to xl and
libxl bits needed for this.

* Reviewed-by pending.

Changes in v6:

- fixed unmap_guest_page().
- fixed flask build.

Changes in v5:

- xl config option renamed to 'max_event_channels'.
- Default set by libxl is 1023.
- Fix flask (I think).
- Use domain_page_map_to_mfn() when unmapping guest pages.
- Coding style (unsigned -> unsigned int throughout, x == NULL -> !x).

Changes in v4:

- Updates for Draft F of the design.
- DOMCTL_set_max_evtchn replaces EVTCHNOP_set_limit.
- Hypervisor defaults to unlimited event channels for for DomU.
- Optimized memory allocation for struct evtchn's when fewer than 128
  are required (see patch 5).
- Added event_channels option to the xl domain configuration file and
  plumbed this through libxl_build_info.  Defaults to 127.

Changes in v3:

- Updates for Draft E of the design.
- Store priority in struct evtchn.
- Implement set_priority with generic code + hook.
- Implement set_limit and add libxc function.
- Add ABI specific output to 'e' debug key.

Changes in v2:

- Updates for Draft D of the design.
- 130,000+ event channels are now supported.
- event_port.c -> event_2l.c and only contains 2l functions.
- Addresses various review comments
  - int -> unsigned in lots of places
  - use write_atomic() to set HEAD
  - removed MAX_EVTCHNS
  - evtchn_ops are const.
- Pack struct evtchns better to reduce memory needed.