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The previous "QEMU shim" proof of concept was taking an approach of only caring about initial spawning of the QEMU process. It was then registered with the libvirtd daemon who took over management of it. The intent was that later libvirtd would be refactored so that the shim retained control over the QEMU monitor and libvirt just forwarded APIs to each shim as needed. This forwarding of APIs would require quite alot of significant refactoring of libvirtd to achieve. This impl thus takes a quite different approach, explicitly deciding to keep the VMs completely separate from those seen & managed by libvirtd. Instead it uses the new "qemu:///embed" URI scheme to embed the entire QEMU driver in the shim, running with a custom root directory. Once the driver is initialization, the shim starts a VM and then waits to shutdown automatically when QEMU shuts down, or should kill QEMU if it is terminated itself. This ought to use the AUTO_DESTROY feature but that is not yet available in embedded mode, so we rely on installing a few signal handlers to gracefully kill QEMU. This isn't reliable if we crash of course, but you can restart with the same root dir. Note this program does not expose any way to manage the QEMU process, since there's no RPC interface enabled. It merely starts the VM and cleans up when the guest shuts down at the end. This program is installed to /usr/bin/virt-qemu-run enabling direct use by end users. Most use cases will probably want to integrate the concept directly into their respective application codebases. This standalone binary serves as a nice demo though, and also provides a way to measure performance of the startup process quite simply. Reviewed-by: Michal Privoznik <mprivozn@redhat.com> Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
libvirt library code README
===========================
The directory provides the bulk of the libvirt codebase. Everything
except for the libvirtd daemon and client tools. The build uses a
large number of libtool convenience libraries - one for each child
directory, and then links them together for the final libvirt.so,
although some bits get linked directly to libvirtd daemon instead.
The files directly in this directory are supporting the public API
entry points & data structures.
There are two core shared modules to be aware of:
* util/ - a collection of shared APIs that can be used by any
code. This directory is always in the include path
for all things built
* conf/ - APIs for parsing / manipulating all the official XML
files used by the public API. This directory is only
in the include path for driver implementation modules
* vmx/ - VMware VMX config handling (used by esx/ and vmware/)
Then there are the hypervisor implementations:
* bhyve - bhyve - The BSD Hypervisor
* esx/ - VMware ESX and GSX support using vSphere API over SOAP
* hyperv/ - Microsoft Hyper-V support using WinRM
* lxc/ - Linux Native Containers
* openvz/ - OpenVZ containers using cli tools
* qemu/ - QEMU / KVM using qemu CLI/monitor
* remote/ - Generic libvirt native RPC client
* test/ - A "mock" driver for testing
* vbox/ - Virtual Box using native API
* vmware/ - VMware Workstation and Player using the vmrun tool
* xen/ - Xen using hypercalls, XenD SEXPR & XenStore
Finally some secondary drivers that are shared for several HVs.
Currently these are used by LXC, OpenVZ, QEMU and Xen drivers.
The ESX, Hyper-V, Remote, Test & VirtualBox drivers all
implement the secondary drivers directly
* cpu/ - CPU feature management
* interface/ - Host network interface management
* network/ - Virtual NAT networking
* nwfilter/ - Network traffic filtering rules
* node_device/ - Host device enumeration
* secret/ - Secret management
* security/ - Mandatory access control drivers
* storage/ - Storage management drivers
Since both the hypervisor and secondary drivers can be built as
dlopen()able modules, it is *FORBIDDEN* to have build dependencies
between these directories. Drivers are only allowed to depend on
the public API, and the internal APIs in the util/ and conf/
directories