Not sure if it's the correct way to add cputune xml for xend driver,
and besides, seems "xm driver" and "xen hypervisor" also support
vcpu affinity, do we need to add support for them too?

LXC driver doesn't support vcpu affinity yet, so just need
to modify it to support cpu shares.

When domain startup, setting cpu affinity and cpu shares according
to the cputune xml specified in domain xml.

Modify "qemudDomainPinVcpu" to update domain config for vcpupin,
and modify "qemuSetSchedulerParameters" to update domain config
for cpu shares.

v1 - v2:
   * Use "VIR_ALLOC_N" instead of "VIR_ALLOC_VAR"
   * But keep raising error when it fails on adding vcpupin xml
     entry, as I still don't have a better idea yet.

Implementations of following functions:
  virDomainVcpupinIsDuplicate
  virDomainVcpupinFindByVcpu
  virDomainVcpupinAdd

Update "virDomainDefParseXML" to parse, and "virDomainDefFormatXML"
to build cputune xml, also implementations of new internal helper
functions.

v1 - v2:
  * Resolve potential crash bug of "virDomainVcpupinAdd"

Also related new functions' declaration, and expose the new introduced
functions in libvirt_private.syms.

v1 - v2:
  Don't expose "virAllocVar" in libvirt_private.syms

v1 - v3:
  * More clear document for "cpu shares", adopted suggestions from
    Matthias Bottle and Daniel Veillard.

v1 - v2:
  * Remove upper limit of cpu shares. (Suggested by Matthias Bottle)

My earlier testing for commit 34fa0de0 was done while starting
just-built libvirt from an unconfined_t shell, where the fds happened
to work when transferring to qemu.  But when installed and run under
virtd_t, failure to label the raw file (with no compression) or the
pipe (with compression) triggers SELinux failures when passing fds
over SCM_RIGHTS to svirt_t qemu.

* src/qemu/qemu_migration.c (qemuMigrationToFile): When passing
FDs, make sure they are labeled.

First fallout of fd: migration - it looks like SELinux enforcing
_does_ require fd labeling (running uninstalled libvirtd from an
unconstrained shell had no problems, but once faked out by doing
 chcon `stat -c %C /usr/sbin/libvirtd` daemon/libvirtd
 run_init $PWD/daemon/libvirtd
to run it with the same context as an init script service, and with
SELinux enforcing, I got a rather confusing failure:
error: Failed to save domain fedora_12 to fed12.img
error: internal error unable to send TAP file handle: No file descriptor supplied via SCM_RIGHTS

This fixes the error message, then I need to figure out a subsequent
patch that does the fsetfilecon() necessary to keep things happy.
It also appears that libvirtd hangs on a failed fd transfer; I don't
know if that needs an independent fix.

* src/qemu/qemu_monitor_text.c (qemuMonitorTextSendFileHandle):
Improve message, since TAP is no longer only client.

* .gitignore: Exclude libvirt_iohelper.

* src/libxl/libxl_driver.c: implements libxlDomainSuspend and
  libxlDomainResume

* src/libxl/libxl_driver.c: implements libxlDomainGetOSType

* src/libxl/libxl_driver.c: implements libxlDomainGetSchedulerType

* src/Makefile.am src/libvirt_private.syms configure.ac: share and
  reuse the sexpr routines from sexpr.h of the old xen driver
* src/libxl/libxl_driver.c: implements libxlDomainXMLFromNative and
  libxlDomainXMLToNative

Hook the virtual cpu functions to their libxenlight counterparts

* src/libxl/libxl_driver.c: implements libxlDomainSetVcpus,
  libxlDomainGetVcpus, libxlDomainSetVcpusFlags,
  libxlDomainGetVcpusFlags and libxlDomainPinVcpu

* src/libxl/libxl_conf.[ch] src/libxl/libxl_driver.[ch]: add authors
  after the licence template

* src/libxl/libxl_conf.h: add the necessary fields to the driver
  private structure
* src/libxl/libxl_driver.c: add lifecycle event support and entry
  points for event(de)register(any)

* src/libxl/libxl_driver.c: use ignore_value() in libxlDomainObjUnref
  and libxlCreateDomEvents

The daemon loops over the linked list of streams when a client
quits, closing any that the client hadn't already closed. Except
it didn't ever move to the next element in the list!

* daemon/stream.c: Fix loop over linked list of streams

* daemon/remote.c, src/remote/remote_driver.c: Implementation
  of storage vol upload/download APIs
* src/remote/remote_protocol.x: Wire protocol definition for
  upload/download
* daemon/remote_dispatch_args.h, daemon/remote_dispatch_prototypes.h,
  daemon/remote_dispatch_table.h, src/remote/remote_protocol.h,
  src/remote/remote_protocol.c: Re-generate

Use generic FD streams to allow data upload/download to/from
any storage volume

* src/storage/storage_driver.c: Wire up upload/download APIs

The new commands vol-upload and vol-download, allow a local file
to be transferred to/from a storage volume.

* tools/virsh.c: Add vol-upload and vol-download commands
* tools/virsh.pod: Document new commands

New APIs are added allowing streaming of content to/from
storage volumes.

* include/libvirt/libvirt.h.in: Add virStorageVolUpload and
  virStorageVolDownload APIs
* src/driver.h, src/libvirt.c, src/libvirt_public.syms: Stub
  code for new APIs
* src/storage/storage_driver.c, src/esx/esx_storage_driver.c:
  Add dummy entries in driver table for new APIs

The O_NONBLOCK flag doesn't work as desired on plain files
or block devices. Introduce an I/O helper program that does
the blocking I/O operations, communicating over a pipe that
can support O_NONBLOCK

* src/fdstream.c, src/fdstream.h: Add non-blocking I/O
  on plain files/block devices
* src/Makefile.am, src/util/iohelper.c: I/O helper program
* src/qemu/qemu_driver.c, src/lxc/lxc_driver.c,
  src/uml/uml_driver.c, src/xen/xen_driver.c: Update for
  streams API change

The example C event loop code is a nasty hack and not compliant
with the require API semantics. Delete this, so that developers
don't mistakenly copy it. Instead call the new public event loop
APIs.

Update the python event loop example, so that it can optionally
use the public event APIs, as an alternative to the pure python
code. The pure python event code is a good working example, so
don't delete it.

Also make the python example use a read only connection to avoid
authentication prompts

* examples/domain-events/events-c/event-test.c: Replace event
  loop code with use of public APIs
* examples/domain-events/events-python/event-test.py: Allow
  optional use of new public event APIs

Regression introduced in commit 6034ddd5.

* src/qemu/qemu_driver.c (qemudDomainSaveFlag): Jump to correct
label.

* src/util/command.c (virCommandAbort) [WIN32]: Provide stub.
Reported by Daniel P. Berrange's autobuilder.

Spawn the compressor ourselves, instead of requiring the shell.

* src/qemu/qemu_migration.c (qemuMigrationToFile): Spawn
compression helper process when needed.

SELinux labeling and cgroup ACLs aren't required if we hand a
pre-opened fd to qemu.  All the more reason to love fd: migration.

* src/qemu/qemu_migration.c (qemuMigrationToFile): Skip steps
that are irrelevant in fd migration.

This points out that core dumps (still) don't work for root-squash
NFS, since the fd is not opened correctly.  This patch should not
introduce any functionality change, it is just a refactoring to
avoid duplicated code.

* src/qemu/qemu_migration.h (qemuMigrationToFile): New prototype.
* src/qemu/qemu_migration.c (qemuMigrationToFile): New function.
* src/qemu/qemu_driver.c (qemudDomainSaveFlag, doCoreDump): Use
it.

Direct access to an open file is so much simpler than passing
everything through a pipe!

* src/qemu/qemu_driver.c (qemudOpenAsUID)
(qemudDomainSaveImageClose): Delete.
(qemudDomainSaveImageOpen): Rename...
(qemuDomainSaveImageOpen): ...and drop read_pid argument.  Use
virFileOpenAs instead of qemudOpenAsUID.
(qemudDomainSaveImageStartVM, qemudDomainRestore)
(qemudDomainObjRestore): Rename...
(qemuDomainSaveImageStartVM, qemuDomainRestore)
(qemDomainObjRestore): ...and simplify accordingly.
(qemudDomainObjStart, qemuDriver): Update callers.

* src/storage/storage_backend.c (createRawFileOpHook): Change
signature.
(struct createRawFileOpHookData): Delete unused struct.
(virStorageBackendCreateRaw): Adjust caller.
* src/qemu/qemu_driver.c (struct fileOpHookData): Delete unused
struct.
(qemudDomainSaveFileOpHook): Rename...
(qemuDomainSaveFileOpHook): ...and change signature.
(qemudDomainSaveFlag): Adjust caller.

Separating the indentation from the real patch made review easier.

* src/util/util.c (virFileOpenAs): Whitespace changes.

This patch intentionally doesn't change indentation, in order to
make it easier to review the real changes.

* src/util/util.h (VIR_FILE_OP_RETURN_FD, virFileOperationHook):
Delete.
(virFileOperation): Rename...
(virFileOpenAs): ...and reduce parameters.
* src/util/util.c (virFileOperationNoFork, virFileOperation):
Rename and simplify.
* src/qemu/qemu_driver.c (qemudDomainSaveFlag): Adjust caller.
* src/storage/storage_backend.c (virStorageBackendCreateRaw):
Likewise.
* src/libvirt_private.syms: Reflect rename.

* src/storage/storage_backend.c (virStorageBackendCreateRaw): Use
new virFileOperation flag.

This makes root-squash NFS saves more efficient.

* src/qemu/qemu_driver.c (qemudDomainSaveFlag): Use new
virFileOperation flag to open fd only once.

Currently, the hook function in virFileOperation is extremely limited:
it must be async-signal-safe, and cannot modify any memory in the
parent process.  It is much handier to return a valid fd and operate
on it in the parent than to deal with hook restrictions.

* src/util/util.h (VIR_FILE_OP_RETURN_FD): New flag.
* src/util/util.c (virFileOperationNoFork, virFileOperation):
Honor new flag.

This allows direct saves (no compression, no root-squash NFS) to use
the more efficient fd: migration, which in turn avoids a race where
qemu exec: migration can sometimes fail because qemu does a generic
waitpid() that conflicts with the pclose() used by exec:.  Further
patches will solve compression and root-squash NFS.

* src/qemu/qemu_driver.c (qemudDomainSaveFlag): Use new function
when there is no compression.

Latent bug introduced in commit 2d6a5819 (Aug 2009), but not exposed
until commit 1859939a (Jan 2011).  Basically, when virExec creates a
pipe, it always marks libvirt's side as cloexec.  If libvirt then
wants to hand that pipe to another child process, things work great if
the fd is dup2()'d onto stdin or stdout (as with stdin: or exec:
migration), but if the pipe is instead used as-is (such as with fd:
migration) then qemu sees EBADF because the fd was closed at exec().

This is a minimal fix for the problem at hand; it is slightly racy,
but no more racy than the rest of libvirt fd handling, including the
case of uncompressed save images.  A more invasive fix, but ultimately
safer at avoiding leaking unintended fds, would be to _always and
atomically_ open all fds as cloexec in libvirt (thanks to primitives
like open(O_CLOEXEC), pipe2(), accept4(), ...), then teach virExec to
clear that bit for all fds explicitly marked to be handed to the child
only after forking.

* src/qemu/qemu_command.c (qemuBuildCommandLine): Clear cloexec
flag.
* tests/qemuxml2argvtest.c (testCompareXMLToArgvFiles): Tweak test.

* src/util/util.h (virSetInherit): New prototype.
* src/util/util.c (virSetCloseExec): Move guts...
(virSetInherit): ...to new function, and allow clearing.
* src/libvirt_private.syms (util.h): Export it.