[PATCH v6 00/11] libxl: Enable save/restore/migration of a restricted QEMU + libxl__ev_qmp_*

[Anthony PERARD <anthony.perard@citrix.com>]

Changes in v6:
    Implementation of libxl__ev_qmp_* functions have been squashed to a single
    patch. And with that, a lot of changes in order to make it simpler to read
    the implementation, have better error reporting and a few bug fix.

    Checkout more detail changelog in the notes of each patch, as there is
    many.

Changes in v5:
    Plenty of patch have been applied.
    Other changes mostly are coding style and other typos.
    Some bug fixes.
    Details can be found in patch notes.

    I have left aside the change to cdrom_insert until I can found what to do
    with the userdata lock.

Changes in v4:
    Better API which meant a lot of other changes.

In order for libxl to be able to manage QEMU while it is restricted, a few
changes are needed. We need a new way to get a startup notification from QEMU
as xenstore may not be accessible when QEMU is ready. We also need to a
different way to have QEMU save it's state and to insert cdrom as a restricted
QEMU doesn't have access to the file system.

For both, we can use QMP, we can use it to query QEMU's status, and we can use
it to send a file descriptor through which QEMU can save its state, or it can
be a cdrom.

We take this opportunity to rewrite the QMP client, and this time been
asynchronous, the result is libxl__ev_qmp_*.

The plat de résistance in this patch series start with patch
"libxl: Design of an async API to issue QMP commands to QEMU"
which implement libxl__ev_qmp_* functions to turn the QMP client into
asynchronous mode.

This comes with changes that uses the new interface.
* "libxl: QEMU startup sync based on QMP"
  which can use QMP to find out when QEMU as started.
  this requires: "libxl_dm: Pre-open QMP socket for QEMU"
  But that only works with dm_restrict=1 as explain in the patch.
* "libxl: Re-implement domain_suspend_device_model using libxl__ev_qmp"
  Which rewrite libxl__qmp_save(), and adds the ability to have QEMU save
  its state to a file descriptor which libxl will have openned.

Patches series available in a git tag:
git fetch https://xenbits.xen.org/git-http/people/aperard/xen-unstable.git tags/libxl-ev-qmp-v6
git checkout -b libxl-ev-qmp-v6 FETCH_HEAD

Cheers,

Anthony PERARD (11):
  libxl: Enhance libxl__sendmsg_fds to deal with EINTR and EWOULDBLOCK
  libxl_qmp: Separate QMP message generation from qmp_send_prepare
  libxl_qmp: Change qmp_qemu_check_version to compare version
  libxl: Design of an async API to issue QMP commands to QEMU
  libxl_qmp: Implementation of libxl__ev_qmp_*
  libxl_exec: Add libxl__spawn_initiate_failure
  libxl_dm: Pre-open QMP socket for QEMU
  libxl: QEMU startup sync based on QMP
  libxl_qmp: Store advertised QEMU version in libxl__ev_qmp
  libxl: Change libxl__domain_suspend_device_model() to be async
  libxl: Re-implement domain_suspend_device_model using libxl__ev_qmp

 tools/libxl/libxl_create.c      |  38 +-
 tools/libxl/libxl_dm.c          | 126 ++++-
 tools/libxl/libxl_dom_suspend.c |  37 +-
 tools/libxl/libxl_exec.c        |  11 +
 tools/libxl/libxl_internal.h    | 162 +++++-
 tools/libxl/libxl_qmp.c         | 925 ++++++++++++++++++++++++++++++--
 tools/libxl/libxl_types.idl     |   7 +
 tools/libxl/libxl_utils.c       |  19 +-
 8 files changed, 1222 insertions(+), 103 deletions(-)

-- 
Anthony PERARD


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