[libvirt] [PATCH 0/5] Support embedding the QEMU driver in client apps directly

[Daniel P. Berrangé]

This patch series proposes a new way to build a "libvirt QEMU shim"
which supports more use cases than the previous approach from last year,
as well as being vastly simpler to implement.

Specifically

 - We can use this to embed the QEMU driver in unit tests allowing
   the full range of odriver functionality to be exercised during
   *unit* testing without interfering with the host OS libvirtd.

 - Apps like libguestfs can embed the QEMU driver to allow them to
   spawn VMs that are immediate children of their app, thus inheriting
   process context, as well as hiding these "service VM" from the
   main libvirtd.

   This would avoid a common irritation where libguestfs VMs suddenly
   appear & disappear in virt-manager's VM list.

 - Apps like kubevirt could use this to eliminate the need to use the
   RPC layer for libvirt. It can directly embed the QEMU driver giving
   it more direct control over how it is run & again inheriting process
   state. This is useful for kubevirt's  one VM per container model
   where Kubernetes itself provides the aggregated view, thus making
   libvirtd's aggregated view redundant

 - The previous shim was very much one shim == one QEMU process. This
   new embed approach supports that of course, but there's also the
   option to run multiple VMs if desired.

 - Using a virtual root directory for QEMU driver state meams we do
   not need to solve the hard refactoring problem of getting the main
   libvirtd to detect the VMs launched via the shim. They can safely
   live independantly.

 - Thanks to the driver refactoring work it is still possible for the
   embedded drivers to talk to main libvirtd to use the secondary
   drivers for storage/network/etc if needed. Ideally we would allow
   those secondary drivers to be embedded too but that's not implemented
   here. Most important would be the secrets driver. Other drivers are
   much less important.

Daniel P. Berrangé (5):
  access: report an error if no access manager is present
  libvirt: pass a root directory path into drivers
  qemu: honour the root parameter during driver initialization
  libvirt: support an "embed" URI path selector for QEMU driver
  qemu: introduce a new style libvirt_qemu_shim program

 src/access/viraccessmanager.c           |  5 ++
 src/driver-state.h                      |  1 +
 src/interface/interface_backend_netcf.c |  1 +
 src/interface/interface_backend_udev.c  |  1 +
 src/libvirt.c                           | 41 ++++++++++++++-
 src/libvirt_internal.h                  |  1 +
 src/libxl/libxl_driver.c                |  1 +
 src/lxc/lxc_driver.c                    |  2 +
 src/network/bridge_driver.c             |  1 +
 src/node_device/node_device_hal.c       |  1 +
 src/node_device/node_device_udev.c      |  1 +
 src/nwfilter/nwfilter_driver.c          |  1 +
 src/qemu/Makefile.inc.am                |  7 +++
 src/qemu/qemu_conf.c                    | 41 +++++++++------
 src/qemu/qemu_conf.h                    |  3 +-
 src/qemu/qemu_driver.c                  |  9 ++--
 src/qemu/qemu_shim.c                    | 70 +++++++++++++++++++++++++
 src/remote/remote_daemon.c              |  1 +
 src/remote/remote_driver.c              |  8 +++
 src/secret/secret_driver.c              |  1 +
 src/storage/storage_driver.c            |  1 +
 src/vz/vz_driver.c                      |  1 +
 22 files changed, 179 insertions(+), 20 deletions(-)
 create mode 100644 src/qemu/qemu_shim.c

-- 
2.21.0