[Qemu-devel] [RFC PATCH v3 00/11] qemu-ga: fsfreeze on Windows using VSS

[Tomoki Sekiyama]

Hi,

This patch series adds fsfreeze support for Windows qemu-guest-agent.

changes from v2:
 - [06/11] Fix errors in Windows 7, reported by Li Baiqing
           (see below for details).

changes from v1: 
 - Fix out-tree build by stop using recursive Makefile
 - Added script to extract VSS SDK headers on POSIX systems using msitools
   (thanks Paolo)
 - Remove some unnecessary header files

v2: http://lists.gnu.org/archive/html/qemu-devel/2013-04/msg02518.html


* Description
  In Windows, VSS (Volume Shadow Copy Service) provides a facility to
  quiesce filesystems and applications before disk snapshots are taken.
  This patch series implements "fsfreeze" command of qemu-ga using VSS.


* How to build & run qemu-ga with VSS support

 - Download Microsoft VSS SDK from:
   http://www.microsoft.com/en-us/download/details.aspx?id=23490

 - Setup the SDK
   scripts/extract-vsssdk-headers setup.exe (on POSIX-systems)

 - Specify installed SDK directory to configure option as:
   ./configure -with-vss-sdk="path/to/VSS SDK" --cross-prefix=i686-w64-mingw32-

 - make qemu-ga.exe

 - Install qemu-ga.exe, qga/vss-win32-provider/qga-provider.{dll,tlb}, and
   the other required mingw libraries into the same directory in guests

 - Run `qemu-ga.exe -s install' and `net start qemu-ga' in the guests


* About errors in Windows 7 with patch v2
  VSS requires to write to snapshot volumes just before making them read-only
  at final commit phase. This feature is called `auto-recovery'
  (See 
http://msdn.microsoft.com/en-us/library/windows/desktop/aa384651(v=vs.85).aspx#base.vssgloss_auto_recoved_shadow_copy
 for details).

  Since qemu and libvirt don't have feature to handle writable snapshots,
  this patchset just disables auto-recovery by specifying
  VSS_VOLSNAP_ATTR_NO_AUTORECOVERY flag to SetContext.
  Unfortunately, this flag seems unsupported in Windows 7 or earlier.
  It tries to look up the snapshot volumes to write and fails in
  VSS_E_OBJECT_NOT_FOUND.

  For fundamental resolution we need a framework for guests to query snapshots
  and to mount them as writable snapshots, but we just ignore the error in
  this patchset.

Any feedback are appliciated.

---
Tomoki Sekiyama (11):
      configure: Support configuring c++ compiler
      Fix errors and warnings while compiling with c++ compilier
      Add a script to extract VSS SDK headers on POSIX system
      qemu-ga: Add an configure option to specify path to Windows VSS SDK
      qemu-ga: Add Windows VSS provider to quiesce applications on fsfreeze
      qemu-ga: Add Windows VSS requester to quisce applications and filesystems
      qemu-ga: call Windows VSS requester in fsfreeze command handler
      qemu-ga: install Windows VSS provider on `qemu-ga -s install'
      qemu-ga: Add VSS provider .tlb file in the repository
      QMP/qemu-ga-client: make timeout longer for guest-fsfreeze-freeze command
      QMP/qmp.py: set locale for exceptions to display non-ascii messages 
correctly


 .gitignore                              |    1 
 Makefile                                |    3 
 Makefile.objs                           |    2 
 QMP/qemu-ga-client                      |    4 
 QMP/qmp.py                              |    4 
 configure                               |   59 ++++
 hmp.c                                   |    2 
 hw/pci/pci.c                            |    2 
 qga/Makefile.objs                       |    7 
 qga/commands-win32.c                    |   74 ++++-
 qga/main.c                              |   41 +++
 qga/vss-win32-provider.h                |   26 ++
 qga/vss-win32-provider/Makefile.objs    |   25 ++
 qga/vss-win32-provider/install.cpp      |  494 +++++++++++++++++++++++++++++++
 qga/vss-win32-provider/provider.cpp     |  474 ++++++++++++++++++++++++++++++
 qga/vss-win32-provider/qga-provider.def |   10 +
 qga/vss-win32-provider/qga-provider.idl |   20 +
 qga/vss-win32-provider/qga-provider.tlb |  Bin
 qga/vss-win32-requester.cpp             |  404 +++++++++++++++++++++++++
 qga/vss-win32-requester.h               |   31 ++
 qga/vss-win32.h                         |   85 +++++
 rules.mak                               |    9 +
 scripts/extract-vsssdk-headers          |   25 ++
 scripts/qapi.py                         |    9 +
 24 files changed, 1796 insertions(+), 15 deletions(-)
 create mode 100644 qga/vss-win32-provider.h
 create mode 100644 qga/vss-win32-provider/Makefile.objs
 create mode 100644 qga/vss-win32-provider/install.cpp
 create mode 100644 qga/vss-win32-provider/provider.cpp
 create mode 100644 qga/vss-win32-provider/qga-provider.def
 create mode 100644 qga/vss-win32-provider/qga-provider.idl
 create mode 100644 qga/vss-win32-provider/qga-provider.tlb
 create mode 100644 qga/vss-win32-requester.cpp
 create mode 100644 qga/vss-win32-requester.h
 create mode 100644 qga/vss-win32.h
 create mode 100755 scripts/extract-vsssdk-headers