qemu-ga: Add Windows VSS provider and requester as DLL

Adds VSS provider and requester as a qga-vss.dll, which is loaded by
Windows VSS service as well as by qemu-ga.

"provider.cpp" implements a basic stub of a software VSS provider.
Currently, this module only relays a frozen event from VSS service to the
agent, and thaw event from the agent to VSS service, to block VSS process
to keep the system frozen while snapshots are taken at the host.

To register the provider to the guest system as COM+ application, the type
library (.tlb) for qga-vss.dll is required. To build it from COM IDL (.idl),
VisualC++, MIDL and stdole2.tlb in Windows SDK are required. This patch also
adds pre-compiled .tlb file in the repository in order to enable
cross-compile qemu-ga.exe for Windows with VSS support.

"requester.cpp" provides the VSS requester to kick the VSS snapshot process.
Qemu-ga.exe works without the DLL, although fsfreeze features are disabled.

These functions are only supported in Windows 2003 or later. In older
systems, fsfreeze features are disabled.

In several versions of Windows which don't support attribute
VSS_VOLSNAP_ATTR_NO_AUTORECOVERY, DoSnapshotSet fails with error
VSS_E_OBJECT_NOT_FOUND. In this patch, we just ignore this error.
To solve this fundamentally, we need a framework to handle mount writable
snapshot on guests, which is required by VSS auto-recovery feature
(cleanup phase after a snapshot is taken).

Signed-off-by: Tomoki Sekiyama <tomoki.sekiyama@hds.com>
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

9 files changed, 1715 insertions, 0 deletions

diff --git a/qga/vss-win32/Makefile.objs b/qga/vss-win32/Makefile.objs
new file mode 100644
index 0000000000..6a69d5008d
--- /dev/null
+++ b/qga/vss-win32/Makefile.objs
@@ -0,0 +1,23 @@
+# rules to build qga-vss.dll
+
+qga-vss-dll-obj-y += requester.o provider.o install.o
+
+obj-qga-vss-dll-obj-y = $(addprefix $(obj)/, $(qga-vss-dll-obj-y))
+$(obj-qga-vss-dll-obj-y): QEMU_CXXFLAGS = $(filter-out -Wstrict-prototypes -Wmissing-prototypes -Wnested-externs -Wold-style-declaration -Wold-style-definition -Wredundant-decls -fstack-protector-all, $(QEMU_CFLAGS)) -Wno-unknown-pragmas -Wno-delete-non-virtual-dtor
+
+$(obj)/qga-vss.dll: LDFLAGS = -shared -Wl,--add-stdcall-alias,--enable-stdcall-fixup -lole32 -loleaut32 -lshlwapi -luuid -static
+$(obj)/qga-vss.dll: $(obj-qga-vss-dll-obj-y) $(SRC_PATH)/$(obj)/qga-vss.def
+	$(call quiet-command,$(CXX) -o $@ $(qga-vss-dll-obj-y) $(SRC_PATH)/qga/vss-win32/qga-vss.def $(CXXFLAGS) $(LDFLAGS),"  LINK  $(TARGET_DIR)$@")
+
+
+# rules to build qga-provider.tlb
+# Currently, only native build is supported because building .tlb
+# (TypeLibrary) from .idl requires WindowsSDK and MIDL (and cl.exe in VC++).
+MIDL=$(WIN_SDK)/Bin/midl
+
+$(obj)/qga-vss.tlb: $(SRC_PATH)/$(obj)/qga-vss.idl
+ifeq ($(WIN_SDK),"")
+	$(call quiet-command,cp $(dir $<)qga-vss.tlb $@, "  COPY  $(TARGET_DIR)$@")
+else
+	$(call quiet-command,$(MIDL) -tlb $@ -I $(WIN_SDK)/Include $<,"  MIDL  $(TARGET_DIR)$@")
+endif
diff --git a/qga/vss-win32/install.cpp b/qga/vss-win32/install.cpp
new file mode 100644
index 0000000000..37731a7271
--- /dev/null
+++ b/qga/vss-win32/install.cpp
@@ -0,0 +1,458 @@
+/*
+ * QEMU Guest Agent win32 VSS Provider installer
+ *
+ * Copyright Hitachi Data Systems Corp. 2013
+ *
+ * Authors:
+ *  Tomoki Sekiyama   <tomoki.sekiyama@hds.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#include <stdio.h>
+#include <string.h>
+
+#include "vss-common.h"
+#include "inc/win2003/vscoordint.h"
+
+#include <comadmin.h>
+#include <wbemidl.h>
+#include <comdef.h>
+#include <comutil.h>
+
+extern HINSTANCE g_hinstDll;
+
+const GUID CLSID_COMAdminCatalog = { 0xF618C514, 0xDFB8, 0x11d1,
+    {0xA2, 0xCF, 0x00, 0x80, 0x5F, 0xC7, 0x92, 0x35} };
+const GUID IID_ICOMAdminCatalog = { 0xDD662187, 0xDFC2, 0x11d1,
+    {0xA2, 0xCF, 0x00, 0x80, 0x5F, 0xC7, 0x92, 0x35} };
+const GUID CLSID_WbemLocator = { 0x4590f811, 0x1d3a, 0x11d0,
+    {0x89, 0x1f, 0x00, 0xaa, 0x00, 0x4b, 0x2e, 0x24} };
+const GUID IID_IWbemLocator = { 0xdc12a687, 0x737f, 0x11cf,
+    {0x88, 0x4d, 0x00, 0xaa, 0x00, 0x4b, 0x2e, 0x24} };
+
+void errmsg(DWORD err, const char *text)
+{
+    /*
+     * `text' contains function call statement when errmsg is called via chk().
+     * To make error message more readable, we cut off the text after '('.
+     * If text doesn't contains '(', negative precision is given, which is
+     * treated as though it were missing.
+     */
+    char *msg = NULL, *nul = strchr(text, '(');
+    int len = nul ? nul - text : -1;
+
+    FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER |
+                  FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS,
+                  NULL, err, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
+                  (char *)&msg, 0, NULL);
+    fprintf(stderr, "%.*s. (Error: %lx) %s\n", len, text, err, msg);
+    LocalFree(msg);
+}
+
+static void errmsg_dialog(DWORD err, const char *text, const char *opt = "")
+{
+    char *msg, buf[512];
+
+    FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER |
+                  FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS,
+                  NULL, err, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
+                  (char *)&msg, 0, NULL);
+    snprintf(buf, sizeof(buf), "%s%s. (Error: %lx) %s", text, opt, err, msg);
+    MessageBox(NULL, buf, "Error from " QGA_PROVIDER_NAME, MB_OK|MB_ICONERROR);
+    LocalFree(msg);
+}
+
+#define _chk(hr, status, msg, err_label)        \
+    do {                                        \
+        hr = (status);                          \
+        if (FAILED(hr)) {                       \
+            errmsg(hr, msg);                    \
+            goto err_label;                     \
+        }                                       \
+    } while (0)
+
+#define chk(status) _chk(hr, status, "Failed to " #status, out)
+
+void __stdcall _com_issue_error(HRESULT hr)
+{
+    errmsg(hr, "Unexpected error in COM");
+}
+
+template<class T>
+HRESULT put_Value(ICatalogObject *pObj, LPCWSTR name, T val)
+{
+    return pObj->put_Value(_bstr_t(name), _variant_t(val));
+}
+
+/* Lookup Administrators group name from winmgmt */
+static HRESULT GetAdminName(_bstr_t *name)
+{
+    HRESULT hr;
+    COMPointer<IWbemLocator> pLoc;
+    COMPointer<IWbemServices> pSvc;
+    COMPointer<IEnumWbemClassObject> pEnum;
+    COMPointer<IWbemClassObject> pWobj;
+    ULONG returned;
+    _variant_t var;
+
+    chk(CoCreateInstance(CLSID_WbemLocator, NULL, CLSCTX_INPROC_SERVER,
+                         IID_IWbemLocator, (LPVOID *)pLoc.replace()));
+    chk(pLoc->ConnectServer(_bstr_t(L"ROOT\\CIMV2"), NULL, NULL, NULL,
+                            0, 0, 0, pSvc.replace()));
+    chk(CoSetProxyBlanket(pSvc, RPC_C_AUTHN_WINNT, RPC_C_AUTHZ_NONE,
+                          NULL, RPC_C_AUTHN_LEVEL_CALL,
+                          RPC_C_IMP_LEVEL_IMPERSONATE, NULL, EOAC_NONE));
+    chk(pSvc->ExecQuery(_bstr_t(L"WQL"),
+                        _bstr_t(L"select * from Win32_Account where "
+                                "SID='S-1-5-32-544' and localAccount=TRUE"),
+                        WBEM_FLAG_RETURN_IMMEDIATELY | WBEM_FLAG_FORWARD_ONLY,
+                        NULL, pEnum.replace()));
+    if (!pEnum) {
+        hr = E_FAIL;
+        errmsg(hr, "Failed to query for Administrators");
+        goto out;
+    }
+    chk(pEnum->Next(WBEM_INFINITE, 1, pWobj.replace(), &returned));
+    if (returned == 0) {
+        hr = E_FAIL;
+        errmsg(hr, "No Administrators found");
+        goto out;
+    }
+
+    chk(pWobj->Get(_bstr_t(L"Name"), 0, &var, 0, 0));
+    try {
+        *name = var;
+    } catch(...) {
+        hr = E_FAIL;
+        errmsg(hr, "Failed to get name of Administrators");
+        goto out;
+    }
+
+out:
+    return hr;
+}
+
+/* Find and iterate QGA VSS provider in COM+ Application Catalog */
+static HRESULT QGAProviderFind(
+    HRESULT (*found)(ICatalogCollection *, int, void *), void *arg)
+{
+    HRESULT hr;
+    COMInitializer initializer;
+    COMPointer<IUnknown> pUnknown;
+    COMPointer<ICOMAdminCatalog> pCatalog;
+    COMPointer<ICatalogCollection> pColl;
+    COMPointer<ICatalogObject> pObj;
+    _variant_t var;
+    long i, n;
+
+    chk(CoCreateInstance(CLSID_COMAdminCatalog, NULL, CLSCTX_INPROC_SERVER,
+                         IID_IUnknown, (void **)pUnknown.replace()));
+    chk(pUnknown->QueryInterface(IID_ICOMAdminCatalog,
+                                 (void **)pCatalog.replace()));
+    chk(pCatalog->GetCollection(_bstr_t(L"Applications"),
+                                (IDispatch **)pColl.replace()));
+    chk(pColl->Populate());
+
+    chk(pColl->get_Count(&n));
+    for (i = n - 1; i >= 0; i--) {
+        chk(pColl->get_Item(i, (IDispatch **)pObj.replace()));
+        chk(pObj->get_Value(_bstr_t(L"Name"), &var));
+        if (var == _variant_t(QGA_PROVIDER_LNAME)) {
+            if (FAILED(found(pColl, i, arg))) {
+                goto out;
+            }
+        }
+    }
+    chk(pColl->SaveChanges(&n));
+
+out:
+    return hr;
+}
+
+/* Count QGA VSS provider in COM+ Application Catalog */
+static HRESULT QGAProviderCount(ICatalogCollection *coll, int i, void *arg)
+{
+    (*(int *)arg)++;
+    return S_OK;
+}
+
+/* Remove QGA VSS provider from COM+ Application Catalog Collection */
+static HRESULT QGAProviderRemove(ICatalogCollection *coll, int i, void *arg)
+{
+    HRESULT hr;
+
+    fprintf(stderr, "Removing COM+ Application: %s\n", QGA_PROVIDER_NAME);
+    chk(coll->Remove(i));
+out:
+    return hr;
+}
+
+/* Unregister this module from COM+ Applications Catalog */
+STDAPI COMUnregister(void)
+{
+    HRESULT hr;
+
+    DllUnregisterServer();
+    chk(QGAProviderFind(QGAProviderRemove, NULL));
+out:
+    return hr;
+}
+
+/* Register this module to COM+ Applications Catalog */
+STDAPI COMRegister(void)
+{
+    HRESULT hr;
+    COMInitializer initializer;
+    COMPointer<IUnknown> pUnknown;
+    COMPointer<ICOMAdminCatalog> pCatalog;
+    COMPointer<ICatalogCollection> pApps, pRoles, pUsersInRole;
+    COMPointer<ICatalogObject> pObj;
+    long n;
+    _bstr_t name;
+    _variant_t key;
+    CHAR dllPath[MAX_PATH], tlbPath[MAX_PATH];
+    bool unregisterOnFailure = false;
+    int count = 0;
+
+    if (!g_hinstDll) {
+        errmsg(E_FAIL, "Failed to initialize DLL");
+        return E_FAIL;
+    }
+
+    chk(QGAProviderFind(QGAProviderCount, (void *)&count));
+    if (count) {
+        errmsg(E_ABORT, "QGA VSS Provider is already installed");
+        return E_ABORT;
+    }
+
+    chk(CoCreateInstance(CLSID_COMAdminCatalog, NULL, CLSCTX_INPROC_SERVER,
+                         IID_IUnknown, (void **)pUnknown.replace()));
+    chk(pUnknown->QueryInterface(IID_ICOMAdminCatalog,
+                                 (void **)pCatalog.replace()));
+
+    /* Install COM+ Component */
+
+    chk(pCatalog->GetCollection(_bstr_t(L"Applications"),
+                                (IDispatch **)pApps.replace()));
+    chk(pApps->Populate());
+    chk(pApps->Add((IDispatch **)&pObj));
+    chk(put_Value(pObj, L"Name",        QGA_PROVIDER_LNAME));
+    chk(put_Value(pObj, L"Description", QGA_PROVIDER_LNAME));
+    chk(put_Value(pObj, L"ApplicationAccessChecksEnabled", true));
+    chk(put_Value(pObj, L"Authentication",                 short(6)));
+    chk(put_Value(pObj, L"AuthenticationCapability",       short(2)));
+    chk(put_Value(pObj, L"ImpersonationLevel",             short(2)));
+    chk(pApps->SaveChanges(&n));
+
+    /* The app should be deleted if something fails after SaveChanges */
+    unregisterOnFailure = true;
+
+    chk(pObj->get_Key(&key));
+
+    if (!GetModuleFileName(g_hinstDll, dllPath, sizeof(dllPath))) {
+        hr = HRESULT_FROM_WIN32(GetLastError());
+        errmsg(hr, "GetModuleFileName failed");
+        goto out;
+    }
+    n = strlen(dllPath);
+    if (n < 3) {
+        hr = E_FAIL;
+        errmsg(hr, "Failed to lookup dll");
+        goto out;
+    }
+    strcpy(tlbPath, dllPath);
+    strcpy(tlbPath+n-3, "tlb");
+    fprintf(stderr, "Registering " QGA_PROVIDER_NAME ":\n");
+    fprintf(stderr, "  %s\n", dllPath);
+    fprintf(stderr, "  %s\n", tlbPath);
+    if (!PathFileExists(tlbPath)) {
+        hr = HRESULT_FROM_WIN32(ERROR_FILE_NOT_FOUND);
+        errmsg(hr, "Failed to lookup tlb");
+        goto out;
+    }
+
+    chk(pCatalog->InstallComponent(_bstr_t(QGA_PROVIDER_LNAME),
+                                   _bstr_t(dllPath), _bstr_t(tlbPath),
+                                   _bstr_t("")));
+
+    /* Setup roles of the applicaion */
+
+    chk(pApps->GetCollection(_bstr_t(L"Roles"), key,
+                             (IDispatch **)pRoles.replace()));
+    chk(pRoles->Populate());
+    chk(pRoles->Add((IDispatch **)pObj.replace()));
+    chk(put_Value(pObj, L"Name",        L"Administrators"));
+    chk(put_Value(pObj, L"Description", L"Administrators group"));
+    chk(pRoles->SaveChanges(&n));
+    chk(pObj->get_Key(&key));
+
+    /* Setup users in the role */
+
+    chk(pRoles->GetCollection(_bstr_t(L"UsersInRole"), key,
+                              (IDispatch **)pUsersInRole.replace()));
+    chk(pUsersInRole->Populate());
+
+    chk(pUsersInRole->Add((IDispatch **)pObj.replace()));
+    chk(GetAdminName(&name));
+    chk(put_Value(pObj, L"User", _bstr_t(".\\") + name));
+
+    chk(pUsersInRole->Add((IDispatch **)pObj.replace()));
+    chk(put_Value(pObj, L"User", L"SYSTEM"));
+    chk(pUsersInRole->SaveChanges(&n));
+
+out:
+    if (unregisterOnFailure && FAILED(hr)) {
+        COMUnregister();
+    }
+
+    return hr;
+}
+
+
+static BOOL CreateRegistryKey(LPCTSTR key, LPCTSTR value, LPCTSTR data)
+{
+    HKEY  hKey;
+    LONG  ret;
+    DWORD size;
+
+    ret = RegCreateKeyEx(HKEY_CLASSES_ROOT, key, 0, NULL,
+        REG_OPTION_NON_VOLATILE, KEY_WRITE, NULL, &hKey, NULL);
+    if (ret != ERROR_SUCCESS) {
+        goto out;
+    }
+
+    if (data != NULL) {
+        size = strlen(data) + 1;
+    } else {
+        size = 0;
+    }
+
+    ret = RegSetValueEx(hKey, value, 0, REG_SZ, (LPBYTE)data, size);
+    RegCloseKey(hKey);
+
+out:
+    if (ret != ERROR_SUCCESS) {
+        /* As we cannot printf within DllRegisterServer(), show a dialog. */
+        errmsg_dialog(ret, "Cannot add registry", key);
+        return FALSE;
+    }
+    return TRUE;
+}
+
+/* Register this dll as a VSS provider */
+STDAPI DllRegisterServer(void)
+{
+    COMInitializer initializer;
+    COMPointer<IVssAdmin> pVssAdmin;
+    HRESULT hr = E_FAIL;
+    char dllPath[MAX_PATH];
+    char key[256];
+
+    if (!g_hinstDll) {
+        errmsg_dialog(hr, "Module instance is not available");
+        goto out;
+    }
+
+    /* Add this module to registery */
+
+    sprintf(key, "CLSID\\%s", g_szClsid);
+    if (!CreateRegistryKey(key, NULL, g_szClsid)) {
+        goto out;
+    }
+
+    if (!GetModuleFileName(g_hinstDll, dllPath, sizeof(dllPath))) {
+        errmsg_dialog(GetLastError(), "GetModuleFileName failed");
+        goto out;
+    }
+
+    sprintf(key, "CLSID\\%s\\InprocServer32", g_szClsid);
+    if (!CreateRegistryKey(key, NULL, dllPath)) {
+        goto out;
+    }
+
+    if (!CreateRegistryKey(key, "ThreadingModel", "Apartment")) {
+        goto out;
+    }
+
+    sprintf(key, "CLSID\\%s\\ProgID", g_szClsid);
+    if (!CreateRegistryKey(key, NULL, g_szProgid)) {
+        goto out;
+    }
+
+    if (!CreateRegistryKey(g_szProgid, NULL, QGA_PROVIDER_NAME)) {
+        goto out;
+    }
+
+    sprintf(key, "%s\\CLSID", g_szProgid);
+    if (!CreateRegistryKey(key, NULL, g_szClsid)) {
+        goto out;
+    }
+
+    hr = CoCreateInstance(CLSID_VSSCoordinator, NULL, CLSCTX_ALL,
+                          IID_IVssAdmin, (void **)pVssAdmin.replace());
+    if (FAILED(hr)) {
+        errmsg_dialog(hr, "CoCreateInstance(VSSCoordinator) failed");
+        goto out;
+    }
+
+    hr = pVssAdmin->RegisterProvider(g_gProviderId, CLSID_QGAVSSProvider,
+                                     const_cast<WCHAR*>(QGA_PROVIDER_LNAME),
+                                     VSS_PROV_SOFTWARE,
+                                     const_cast<WCHAR*>(QGA_PROVIDER_VERSION),
+                                     g_gProviderVersion);
+    if (FAILED(hr)) {
+        errmsg_dialog(hr, "RegisterProvider failed");
+    }
+
+out:
+    if (FAILED(hr)) {
+        DllUnregisterServer();
+    }
+
+    return hr;
+}
+
+/* Unregister this VSS hardware provider from the system */
+STDAPI DllUnregisterServer(void)
+{
+    TCHAR key[256];
+    COMInitializer initializer;
+    COMPointer<IVssAdmin> pVssAdmin;
+
+    HRESULT hr = CoCreateInstance(CLSID_VSSCoordinator,
+                                  NULL, CLSCTX_ALL, IID_IVssAdmin,
+                                  (void **)pVssAdmin.replace());
+    if (SUCCEEDED(hr)) {
+        hr = pVssAdmin->UnregisterProvider(g_gProviderId);
+    } else {
+        errmsg(hr, "CoCreateInstance(VSSCoordinator) failed");
+    }
+
+    sprintf(key, "CLSID\\%s", g_szClsid);
+    SHDeleteKey(HKEY_CLASSES_ROOT, key);
+    SHDeleteKey(HKEY_CLASSES_ROOT, g_szProgid);
+
+    return S_OK; /* Uninstall should never fail */
+}
+
+
+/* Support function to convert ASCII string into BSTR (used in _bstr_t) */
+namespace _com_util
+{
+    BSTR WINAPI ConvertStringToBSTR(const char *ascii) {
+        int len = strlen(ascii);
+        BSTR bstr = SysAllocStringLen(NULL, len);
+
+        if (!bstr) {
+            return NULL;
+        }
+
+        if (mbstowcs(bstr, ascii, len) == (size_t)-1) {
+            fprintf(stderr, "Failed to convert string '%s' into BSTR", ascii);
+            bstr[0] = 0;
+        }
+        return bstr;
+    }
+}
diff --git a/qga/vss-win32/provider.cpp b/qga/vss-win32/provider.cpp
new file mode 100644
index 0000000000..bf42b5e95f
--- /dev/null
+++ b/qga/vss-win32/provider.cpp
@@ -0,0 +1,523 @@
+/*
+ * QEMU Guest Agent win32 VSS Provider implementations
+ *
+ * Copyright Hitachi Data Systems Corp. 2013
+ *
+ * Authors:
+ *  Tomoki Sekiyama   <tomoki.sekiyama@hds.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#include <stdio.h>
+#include "vss-common.h"
+#include "inc/win2003/vscoordint.h"
+#include "inc/win2003/vsprov.h"
+
+#define VSS_TIMEOUT_MSEC (60*1000)
+
+static long g_nComObjsInUse;
+HINSTANCE g_hinstDll;
+
+/* VSS common GUID's */
+
+const CLSID CLSID_VSSCoordinator = { 0xE579AB5F, 0x1CC4, 0x44b4,
+    {0xBE, 0xD9, 0xDE, 0x09, 0x91, 0xFF, 0x06, 0x23} };
+const IID IID_IVssAdmin = { 0x77ED5996, 0x2F63, 0x11d3,
+    {0x8A, 0x39, 0x00, 0xC0, 0x4F, 0x72, 0xD8, 0xE3} };
+
+const IID IID_IVssHardwareSnapshotProvider = { 0x9593A157, 0x44E9, 0x4344,
+    {0xBB, 0xEB, 0x44, 0xFB, 0xF9, 0xB0, 0x6B, 0x10} };
+const IID IID_IVssSoftwareSnapshotProvider = { 0x609e123e, 0x2c5a, 0x44d3,
+    {0x8f, 0x01, 0x0b, 0x1d, 0x9a, 0x47, 0xd1, 0xff} };
+const IID IID_IVssProviderCreateSnapshotSet = { 0x5F894E5B, 0x1E39, 0x4778,
+    {0x8E, 0x23, 0x9A, 0xBA, 0xD9, 0xF0, 0xE0, 0x8C} };
+const IID IID_IVssProviderNotifications = { 0xE561901F, 0x03A5, 0x4afe,
+    {0x86, 0xD0, 0x72, 0xBA, 0xEE, 0xCE, 0x70, 0x04} };
+
+const IID IID_IVssEnumObject = { 0xAE1C7110, 0x2F60, 0x11d3,
+    {0x8A, 0x39, 0x00, 0xC0, 0x4F, 0x72, 0xD8, 0xE3} };
+
+
+void LockModule(BOOL lock)
+{
+    if (lock) {
+        InterlockedIncrement(&g_nComObjsInUse);
+    } else {
+        InterlockedDecrement(&g_nComObjsInUse);
+    }
+}
+
+/* Empty enumerator for VssObject */
+
+class CQGAVSSEnumObject : public IVssEnumObject
+{
+public:
+    STDMETHODIMP QueryInterface(REFIID riid, void **ppObj);
+    STDMETHODIMP_(ULONG) AddRef();
+    STDMETHODIMP_(ULONG) Release();
+
+    /* IVssEnumObject Methods */
+    STDMETHODIMP Next(
+        ULONG celt, VSS_OBJECT_PROP *rgelt, ULONG *pceltFetched);
+    STDMETHODIMP Skip(ULONG celt);
+    STDMETHODIMP Reset(void);
+    STDMETHODIMP Clone(IVssEnumObject **ppenum);
+
+    /* CQGAVSSEnumObject Methods */
+    CQGAVSSEnumObject();
+    ~CQGAVSSEnumObject();
+
+private:
+    long m_nRefCount;
+};
+
+CQGAVSSEnumObject::CQGAVSSEnumObject()
+{
+    m_nRefCount = 0;
+    LockModule(TRUE);
+}
+
+CQGAVSSEnumObject::~CQGAVSSEnumObject()
+{
+    LockModule(FALSE);
+}
+
+STDMETHODIMP CQGAVSSEnumObject::QueryInterface(REFIID riid, void **ppObj)
+{
+    if (riid == IID_IUnknown || riid == IID_IVssEnumObject) {
+        *ppObj = static_cast<void*>(static_cast<IVssEnumObject*>(this));
+        AddRef();
+        return S_OK;
+    }
+    *ppObj = NULL;
+    return E_NOINTERFACE;
+}
+
+STDMETHODIMP_(ULONG) CQGAVSSEnumObject::AddRef()
+{
+    return InterlockedIncrement(&m_nRefCount);
+}
+
+STDMETHODIMP_(ULONG) CQGAVSSEnumObject::Release()
+{
+    long nRefCount = InterlockedDecrement(&m_nRefCount);
+    if (m_nRefCount == 0) {
+        delete this;
+    }
+    return nRefCount;
+}
+
+STDMETHODIMP CQGAVSSEnumObject::Next(
+    ULONG celt, VSS_OBJECT_PROP *rgelt, ULONG *pceltFetched)
+{
+    *pceltFetched = 0;
+    return S_FALSE;
+}
+
+STDMETHODIMP CQGAVSSEnumObject::Skip(ULONG celt)
+{
+    return S_FALSE;
+}
+
+STDMETHODIMP CQGAVSSEnumObject::Reset(void)
+{
+    return S_OK;
+}
+
+STDMETHODIMP CQGAVSSEnumObject::Clone(IVssEnumObject **ppenum)
+{
+    return E_NOTIMPL;
+}
+
+
+/* QGAVssProvider */
+
+class CQGAVssProvider :
+    public IVssSoftwareSnapshotProvider,
+    public IVssProviderCreateSnapshotSet,
+    public IVssProviderNotifications
+{
+public:
+    STDMETHODIMP QueryInterface(REFIID riid, void **ppObj);
+    STDMETHODIMP_(ULONG) AddRef();
+    STDMETHODIMP_(ULONG) Release();
+
+    /* IVssSoftwareSnapshotProvider Methods */
+    STDMETHODIMP SetContext(LONG lContext);
+    STDMETHODIMP GetSnapshotProperties(
+        VSS_ID SnapshotId, VSS_SNAPSHOT_PROP *pProp);
+    STDMETHODIMP Query(
+        VSS_ID QueriedObjectId, VSS_OBJECT_TYPE eQueriedObjectType,
+        VSS_OBJECT_TYPE eReturnedObjectsType, IVssEnumObject **ppEnum);
+    STDMETHODIMP DeleteSnapshots(
+        VSS_ID SourceObjectId, VSS_OBJECT_TYPE eSourceObjectType,
+        BOOL bForceDelete, LONG *plDeletedSnapshots,
+        VSS_ID *pNondeletedSnapshotID);
+    STDMETHODIMP BeginPrepareSnapshot(
+        VSS_ID SnapshotSetId, VSS_ID SnapshotId,
+        VSS_PWSZ pwszVolumeName, LONG lNewContext);
+    STDMETHODIMP IsVolumeSupported(
+        VSS_PWSZ pwszVolumeName, BOOL *pbSupportedByThisProvider);
+    STDMETHODIMP IsVolumeSnapshotted(
+        VSS_PWSZ pwszVolumeName, BOOL *pbSnapshotsPresent,
+        LONG *plSnapshotCompatibility);
+    STDMETHODIMP SetSnapshotProperty(
+        VSS_ID SnapshotId, VSS_SNAPSHOT_PROPERTY_ID eSnapshotPropertyId,
+        VARIANT vProperty);
+    STDMETHODIMP RevertToSnapshot(VSS_ID SnapshotId);
+    STDMETHODIMP QueryRevertStatus(VSS_PWSZ pwszVolume, IVssAsync **ppAsync);
+
+    /* IVssProviderCreateSnapshotSet Methods */
+    STDMETHODIMP EndPrepareSnapshots(VSS_ID SnapshotSetId);
+    STDMETHODIMP PreCommitSnapshots(VSS_ID SnapshotSetId);
+    STDMETHODIMP CommitSnapshots(VSS_ID SnapshotSetId);
+    STDMETHODIMP PostCommitSnapshots(
+        VSS_ID SnapshotSetId, LONG lSnapshotsCount);
+    STDMETHODIMP PreFinalCommitSnapshots(VSS_ID SnapshotSetId);
+    STDMETHODIMP PostFinalCommitSnapshots(VSS_ID SnapshotSetId);
+    STDMETHODIMP AbortSnapshots(VSS_ID SnapshotSetId);
+
+    /* IVssProviderNotifications Methods */
+    STDMETHODIMP OnLoad(IUnknown *pCallback);
+    STDMETHODIMP OnUnload(BOOL bForceUnload);
+
+    /* CQGAVssProvider Methods */
+    CQGAVssProvider();
+    ~CQGAVssProvider();
+
+private:
+    long m_nRefCount;
+};
+
+CQGAVssProvider::CQGAVssProvider()
+{
+    m_nRefCount = 0;
+    LockModule(TRUE);
+}
+
+CQGAVssProvider::~CQGAVssProvider()
+{
+    LockModule(FALSE);
+}
+
+STDMETHODIMP CQGAVssProvider::QueryInterface(REFIID riid, void **ppObj)
+{
+    if (riid == IID_IUnknown) {
+        *ppObj = static_cast<void*>(this);
+        AddRef();
+        return S_OK;
+    }
+    if (riid == IID_IVssSoftwareSnapshotProvider) {
+        *ppObj = static_cast<void*>(
+            static_cast<IVssSoftwareSnapshotProvider*>(this));
+        AddRef();
+        return S_OK;
+    }
+    if (riid == IID_IVssProviderCreateSnapshotSet) {
+        *ppObj = static_cast<void*>(
+            static_cast<IVssProviderCreateSnapshotSet*>(this));
+        AddRef();
+        return S_OK;
+    }
+    if (riid == IID_IVssProviderNotifications) {
+        *ppObj = static_cast<void*>(
+            static_cast<IVssProviderNotifications*>(this));
+        AddRef();
+        return S_OK;
+    }
+    *ppObj = NULL;
+    return E_NOINTERFACE;
+}
+
+STDMETHODIMP_(ULONG) CQGAVssProvider::AddRef()
+{
+    return InterlockedIncrement(&m_nRefCount);
+}
+
+STDMETHODIMP_(ULONG) CQGAVssProvider::Release()
+{
+    long nRefCount = InterlockedDecrement(&m_nRefCount);
+    if (m_nRefCount == 0) {
+        delete this;
+    }
+    return nRefCount;
+}
+
+
+/*
+ * IVssSoftwareSnapshotProvider methods
+ */
+
+STDMETHODIMP CQGAVssProvider::SetContext(LONG lContext)
+{
+    return S_OK;
+}
+
+STDMETHODIMP CQGAVssProvider::GetSnapshotProperties(
+    VSS_ID SnapshotId, VSS_SNAPSHOT_PROP *pProp)
+{
+    return VSS_E_OBJECT_NOT_FOUND;
+}
+
+STDMETHODIMP CQGAVssProvider::Query(
+    VSS_ID QueriedObjectId, VSS_OBJECT_TYPE eQueriedObjectType,
+    VSS_OBJECT_TYPE eReturnedObjectsType, IVssEnumObject **ppEnum)
+{
+    try {
+        *ppEnum = new CQGAVSSEnumObject;
+    } catch (...) {
+        return E_OUTOFMEMORY;
+    }
+    (*ppEnum)->AddRef();
+    return S_OK;
+}
+
+STDMETHODIMP CQGAVssProvider::DeleteSnapshots(
+    VSS_ID SourceObjectId, VSS_OBJECT_TYPE eSourceObjectType,
+    BOOL bForceDelete, LONG *plDeletedSnapshots, VSS_ID *pNondeletedSnapshotID)
+{
+    return E_NOTIMPL;
+}
+
+STDMETHODIMP CQGAVssProvider::BeginPrepareSnapshot(
+    VSS_ID SnapshotSetId, VSS_ID SnapshotId,
+    VSS_PWSZ pwszVolumeName, LONG lNewContext)
+{
+    return S_OK;
+}
+
+STDMETHODIMP CQGAVssProvider::IsVolumeSupported(
+    VSS_PWSZ pwszVolumeName, BOOL *pbSupportedByThisProvider)
+{
+    *pbSupportedByThisProvider = TRUE;
+
+    return S_OK;
+}
+
+STDMETHODIMP CQGAVssProvider::IsVolumeSnapshotted(VSS_PWSZ pwszVolumeName,
+    BOOL *pbSnapshotsPresent, LONG *plSnapshotCompatibility)
+{
+    *pbSnapshotsPresent = FALSE;
+    *plSnapshotCompatibility = 0;
+    return S_OK;
+}
+
+STDMETHODIMP CQGAVssProvider::SetSnapshotProperty(VSS_ID SnapshotId,
+    VSS_SNAPSHOT_PROPERTY_ID eSnapshotPropertyId, VARIANT vProperty)
+{
+    return E_NOTIMPL;
+}
+
+STDMETHODIMP CQGAVssProvider::RevertToSnapshot(VSS_ID SnapshotId)
+{
+    return E_NOTIMPL;
+}
+
+STDMETHODIMP CQGAVssProvider::QueryRevertStatus(
+    VSS_PWSZ pwszVolume, IVssAsync **ppAsync)
+{
+    return E_NOTIMPL;
+}
+
+
+/*
+ * IVssProviderCreateSnapshotSet methods
+ */
+
+STDMETHODIMP CQGAVssProvider::EndPrepareSnapshots(VSS_ID SnapshotSetId)
+{
+    return S_OK;
+}
+
+STDMETHODIMP CQGAVssProvider::PreCommitSnapshots(VSS_ID SnapshotSetId)
+{
+    return S_OK;
+}
+
+STDMETHODIMP CQGAVssProvider::CommitSnapshots(VSS_ID SnapshotSetId)
+{
+    HRESULT hr = S_OK;
+    HANDLE hEventFrozen, hEventThaw, hEventTimeout;
+
+    hEventFrozen = OpenEvent(EVENT_ALL_ACCESS, FALSE, EVENT_NAME_FROZEN);
+    if (hEventFrozen == INVALID_HANDLE_VALUE) {
+        return E_FAIL;
+    }
+
+    hEventThaw = OpenEvent(EVENT_ALL_ACCESS, FALSE, EVENT_NAME_THAW);
+    if (hEventThaw == INVALID_HANDLE_VALUE) {
+        CloseHandle(hEventFrozen);
+        return E_FAIL;
+    }
+
+    hEventTimeout = OpenEvent(EVENT_ALL_ACCESS, FALSE, EVENT_NAME_TIMEOUT);
+    if (hEventTimeout == INVALID_HANDLE_VALUE) {
+        CloseHandle(hEventFrozen);
+        CloseHandle(hEventThaw);
+        return E_FAIL;
+    }
+
+    /* Send event to qemu-ga to notify filesystem is frozen */
+    SetEvent(hEventFrozen);
+
+    /* Wait until the snapshot is taken by the host. */
+    if (WaitForSingleObject(hEventThaw, VSS_TIMEOUT_MSEC) != WAIT_OBJECT_0) {
+        /* Send event to qemu-ga to notify the provider is timed out */
+        SetEvent(hEventTimeout);
+        hr = E_ABORT;
+    }
+
+    CloseHandle(hEventThaw);
+    CloseHandle(hEventFrozen);
+    CloseHandle(hEventTimeout);
+    return hr;
+}
+
+STDMETHODIMP CQGAVssProvider::PostCommitSnapshots(
+    VSS_ID SnapshotSetId, LONG lSnapshotsCount)
+{
+    return S_OK;
+}
+
+STDMETHODIMP CQGAVssProvider::PreFinalCommitSnapshots(VSS_ID SnapshotSetId)
+{
+    return S_OK;
+}
+
+STDMETHODIMP CQGAVssProvider::PostFinalCommitSnapshots(VSS_ID SnapshotSetId)
+{
+    return S_OK;
+}
+
+STDMETHODIMP CQGAVssProvider::AbortSnapshots(VSS_ID SnapshotSetId)
+{
+    return S_OK;
+}
+
+/*
+ * IVssProviderNotifications methods
+ */
+
+STDMETHODIMP CQGAVssProvider::OnLoad(IUnknown *pCallback)
+{
+    return S_OK;
+}
+
+STDMETHODIMP CQGAVssProvider::OnUnload(BOOL bForceUnload)
+{
+    return S_OK;
+}
+
+
+/*
+ * CQGAVssProviderFactory class
+ */
+
+class CQGAVssProviderFactory : public IClassFactory
+{
+public:
+    STDMETHODIMP QueryInterface(REFIID riid, void **ppv);
+    STDMETHODIMP_(ULONG) AddRef();
+    STDMETHODIMP_(ULONG) Release();
+    STDMETHODIMP CreateInstance(
+        IUnknown *pUnknownOuter, REFIID iid, void **ppv);
+    STDMETHODIMP LockServer(BOOL lock) { return E_NOTIMPL; }
+
+    CQGAVssProviderFactory();
+    ~CQGAVssProviderFactory();
+
+private:
+    long m_nRefCount;
+};
+
+CQGAVssProviderFactory::CQGAVssProviderFactory()
+{
+    m_nRefCount = 0;
+    LockModule(TRUE);
+}
+
+CQGAVssProviderFactory::~CQGAVssProviderFactory()
+{
+    LockModule(FALSE);
+}
+
+STDMETHODIMP CQGAVssProviderFactory::QueryInterface(REFIID riid, void **ppv)
+{
+    if (riid == IID_IUnknown || riid == IID_IClassFactory) {
+        *ppv = static_cast<void*>(this);
+        AddRef();
+        return S_OK;
+    }
+    *ppv = NULL;
+    return E_NOINTERFACE;
+}
+
+STDMETHODIMP_(ULONG) CQGAVssProviderFactory::AddRef()
+{
+    return InterlockedIncrement(&m_nRefCount);
+}
+
+STDMETHODIMP_(ULONG) CQGAVssProviderFactory::Release()
+{
+    long nRefCount = InterlockedDecrement(&m_nRefCount);
+    if (m_nRefCount == 0) {
+        delete this;
+    }
+    return nRefCount;
+}
+
+STDMETHODIMP CQGAVssProviderFactory::CreateInstance(
+    IUnknown *pUnknownOuter, REFIID iid, void **ppv)
+{
+    CQGAVssProvider *pObj;
+
+    if (pUnknownOuter) {
+        return CLASS_E_NOAGGREGATION;
+    }
+    try {
+        pObj = new CQGAVssProvider;
+    } catch (...) {
+        return E_OUTOFMEMORY;
+    }
+    HRESULT hr = pObj->QueryInterface(iid, ppv);
+    if (FAILED(hr)) {
+        delete pObj;
+    }
+    return hr;
+}
+
+
+/*
+ * DLL functions
+ */
+
+STDAPI DllGetClassObject(REFCLSID rclsid, REFIID riid, LPVOID *ppv)
+{
+    CQGAVssProviderFactory *factory;
+    try {
+        factory = new CQGAVssProviderFactory;
+    } catch (...) {
+        return E_OUTOFMEMORY;
+    }
+    factory->AddRef();
+    HRESULT hr = factory->QueryInterface(riid, ppv);
+    factory->Release();
+    return hr;
+}
+
+STDAPI DllCanUnloadNow()
+{
+    return g_nComObjsInUse == 0 ? S_OK : S_FALSE;
+}
+
+EXTERN_C
+BOOL WINAPI DllMain(HINSTANCE hinstDll, DWORD dwReason, LPVOID lpReserved)
+{
+    if (dwReason == DLL_PROCESS_ATTACH) {
+        g_hinstDll = hinstDll;
+        DisableThreadLibraryCalls(hinstDll);
+    }
+    return TRUE;
+}
diff --git a/qga/vss-win32/qga-vss.def b/qga/vss-win32/qga-vss.def
new file mode 100644
index 0000000000..927782c31b
--- /dev/null
+++ b/qga/vss-win32/qga-vss.def
@@ -0,0 +1,13 @@
+LIBRARY      "QGA-PROVIDER.DLL"
+
+EXPORTS
+	COMRegister		PRIVATE
+	COMUnregister		PRIVATE
+	DllCanUnloadNow		PRIVATE
+	DllGetClassObject	PRIVATE
+	DllRegisterServer	PRIVATE
+	DllUnregisterServer	PRIVATE
+	requester_init		PRIVATE
+	requester_deinit	PRIVATE
+	requester_freeze	PRIVATE
+	requester_thaw		PRIVATE
diff --git a/qga/vss-win32/qga-vss.idl b/qga/vss-win32/qga-vss.idl
new file mode 100644
index 0000000000..17abca0da5
--- /dev/null
+++ b/qga/vss-win32/qga-vss.idl
@@ -0,0 +1,20 @@
+import "oaidl.idl";
+import "ocidl.idl";
+
+[
+    uuid(103B8142-6CE5-48A7-BDE1-794D3192FCF1),
+    version(1.0),
+    helpstring("QGAVSSProvider Type Library")
+]
+library QGAVSSHWProviderLib
+{
+    importlib("stdole2.tlb");
+    [
+        uuid(6E6A3492-8D4D-440C-9619-5E5D0CC31CA8),
+        helpstring("QGAVSSProvider Class")
+    ]
+    coclass QGAVSSHWProvider
+    {
+        [default] interface IUnknown;
+    };
+};
diff --git a/qga/vss-win32/qga-vss.tlb b/qga/vss-win32/qga-vss.tlb
new file mode 100644
index 0000000000..226452a186
--- /dev/null
+++ b/qga/vss-win32/qga-vss.tlb
diff --git a/qga/vss-win32/requester.cpp b/qga/vss-win32/requester.cpp
new file mode 100644
index 0000000000..1e8dd3dfa8
--- /dev/null
+++ b/qga/vss-win32/requester.cpp
@@ -0,0 +1,507 @@
+/*
+ * QEMU Guest Agent win32 VSS Requester implementations
+ *
+ * Copyright Hitachi Data Systems Corp. 2013
+ *
+ * Authors:
+ *  Tomoki Sekiyama   <tomoki.sekiyama@hds.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#include <stdio.h>
+#include "vss-common.h"
+#include "requester.h"
+#include "assert.h"
+#include "inc/win2003/vswriter.h"
+#include "inc/win2003/vsbackup.h"
+
+/* Max wait time for frozen event (VSS can only hold writes for 10 seconds) */
+#define VSS_TIMEOUT_FREEZE_MSEC 10000
+
+/* Call QueryStatus every 10 ms while waiting for frozen event */
+#define VSS_TIMEOUT_EVENT_MSEC 10
+
+#define err_set(e, err, fmt, ...) \
+    ((e)->error_set((e)->errp, err, (e)->err_class, fmt, ## __VA_ARGS__))
+#define err_is_set(e) ((e)->errp && *(e)->errp)
+
+
+/* Handle to VSSAPI.DLL */
+static HMODULE hLib;
+
+/* Functions in VSSAPI.DLL */
+typedef HRESULT(STDAPICALLTYPE * t_CreateVssBackupComponents)(
+    OUT IVssBackupComponents**);
+typedef void(APIENTRY * t_VssFreeSnapshotProperties)(IN VSS_SNAPSHOT_PROP*);
+static t_CreateVssBackupComponents pCreateVssBackupComponents;
+static t_VssFreeSnapshotProperties pVssFreeSnapshotProperties;
+
+/* Variables used while applications and filesystes are frozen by VSS */
+static struct QGAVSSContext {
+    IVssBackupComponents *pVssbc;  /* VSS requester interface */
+    IVssAsync *pAsyncSnapshot;     /* async info of VSS snapshot operation */
+    HANDLE hEventFrozen;           /* notify fs/writer freeze from provider */
+    HANDLE hEventThaw;             /* request provider to thaw */
+    HANDLE hEventTimeout;          /* notify timeout in provider */
+    int cFrozenVols;               /* number of frozen volumes */
+} vss_ctx;
+
+STDAPI requester_init(void)
+{
+    vss_ctx.hEventFrozen =  INVALID_HANDLE_VALUE;
+    vss_ctx.hEventThaw = INVALID_HANDLE_VALUE;
+    vss_ctx.hEventTimeout = INVALID_HANDLE_VALUE;
+
+    COMInitializer initializer; /* to call CoInitializeSecurity */
+    HRESULT hr = CoInitializeSecurity(
+        NULL, -1, NULL, NULL, RPC_C_AUTHN_LEVEL_PKT_PRIVACY,
+        RPC_C_IMP_LEVEL_IDENTIFY, NULL, EOAC_NONE, NULL);
+    if (FAILED(hr)) {
+        fprintf(stderr, "failed to CoInitializeSecurity (error %lx)\n", hr);
+        return hr;
+    }
+
+    hLib = LoadLibraryA("VSSAPI.DLL");
+    if (!hLib) {
+        fprintf(stderr, "failed to load VSSAPI.DLL\n");
+        return HRESULT_FROM_WIN32(GetLastError());
+    }
+
+    pCreateVssBackupComponents = (t_CreateVssBackupComponents)
+        GetProcAddress(hLib,
+#ifdef _WIN64 /* 64bit environment */
+        "?CreateVssBackupComponents@@YAJPEAPEAVIVssBackupComponents@@@Z"
+#else /* 32bit environment */
+        "?CreateVssBackupComponents@@YGJPAPAVIVssBackupComponents@@@Z"
+#endif
+        );
+    if (!pCreateVssBackupComponents) {
+        fprintf(stderr, "failed to get proc address from VSSAPI.DLL\n");
+        return HRESULT_FROM_WIN32(GetLastError());
+    }
+
+    pVssFreeSnapshotProperties = (t_VssFreeSnapshotProperties)
+        GetProcAddress(hLib, "VssFreeSnapshotProperties");
+    if (!pVssFreeSnapshotProperties) {
+        fprintf(stderr, "failed to get proc address from VSSAPI.DLL\n");
+        return HRESULT_FROM_WIN32(GetLastError());
+    }
+
+    return S_OK;
+}
+
+static void requester_cleanup(void)
+{
+    if (vss_ctx.hEventFrozen != INVALID_HANDLE_VALUE) {
+        CloseHandle(vss_ctx.hEventFrozen);
+        vss_ctx.hEventFrozen = INVALID_HANDLE_VALUE;
+    }
+    if (vss_ctx.hEventThaw != INVALID_HANDLE_VALUE) {
+        CloseHandle(vss_ctx.hEventThaw);
+        vss_ctx.hEventThaw = INVALID_HANDLE_VALUE;
+    }
+    if (vss_ctx.hEventTimeout != INVALID_HANDLE_VALUE) {
+        CloseHandle(vss_ctx.hEventTimeout);
+        vss_ctx.hEventTimeout = INVALID_HANDLE_VALUE;
+    }
+    if (vss_ctx.pAsyncSnapshot) {
+        vss_ctx.pAsyncSnapshot->Release();
+        vss_ctx.pAsyncSnapshot = NULL;
+    }
+    if (vss_ctx.pVssbc) {
+        vss_ctx.pVssbc->Release();
+        vss_ctx.pVssbc = NULL;
+    }
+    vss_ctx.cFrozenVols = 0;
+}
+
+STDAPI requester_deinit(void)
+{
+    requester_cleanup();
+
+    pCreateVssBackupComponents = NULL;
+    pVssFreeSnapshotProperties = NULL;
+    if (hLib) {
+        FreeLibrary(hLib);
+        hLib = NULL;
+    }
+
+    return S_OK;
+}
+
+static HRESULT WaitForAsync(IVssAsync *pAsync)
+{
+    HRESULT ret, hr;
+
+    do {
+        hr = pAsync->Wait();
+        if (FAILED(hr)) {
+            ret = hr;
+            break;
+        }
+        hr = pAsync->QueryStatus(&ret, NULL);
+        if (FAILED(hr)) {
+            ret = hr;
+            break;
+        }
+    } while (ret == VSS_S_ASYNC_PENDING);
+
+    return ret;
+}
+
+static void AddComponents(ErrorSet *errset)
+{
+    unsigned int cWriters, i;
+    VSS_ID id, idInstance, idWriter;
+    BSTR bstrWriterName = NULL;
+    VSS_USAGE_TYPE usage;
+    VSS_SOURCE_TYPE source;
+    unsigned int cComponents, c1, c2, j;
+    COMPointer<IVssExamineWriterMetadata> pMetadata;
+    COMPointer<IVssWMComponent> pComponent;
+    PVSSCOMPONENTINFO info;
+    HRESULT hr;
+
+    hr = vss_ctx.pVssbc->GetWriterMetadataCount(&cWriters);
+    if (FAILED(hr)) {
+        err_set(errset, hr, "failed to get writer metadata count");
+        goto out;
+    }
+
+    for (i = 0; i < cWriters; i++) {
+        hr = vss_ctx.pVssbc->GetWriterMetadata(i, &id, pMetadata.replace());
+        if (FAILED(hr)) {
+            err_set(errset, hr, "failed to get writer metadata of %d/%d",
+                             i, cWriters);
+            goto out;
+        }
+
+        hr = pMetadata->GetIdentity(&idInstance, &idWriter,
+                                    &bstrWriterName, &usage, &source);
+        if (FAILED(hr)) {
+            err_set(errset, hr, "failed to get identity of writer %d/%d",
+                             i, cWriters);
+            goto out;
+        }
+
+        hr = pMetadata->GetFileCounts(&c1, &c2, &cComponents);
+        if (FAILED(hr)) {
+            err_set(errset, hr, "failed to get file counts of %S",
+                             bstrWriterName);
+            goto out;
+        }
+
+        for (j = 0; j < cComponents; j++) {
+            hr = pMetadata->GetComponent(j, pComponent.replace());
+            if (FAILED(hr)) {
+                err_set(errset, hr,
+                                 "failed to get component %d/%d of %S",
+                                 j, cComponents, bstrWriterName);
+                goto out;
+            }
+
+            hr = pComponent->GetComponentInfo(&info);
+            if (FAILED(hr)) {
+                err_set(errset, hr,
+                                 "failed to get component info %d/%d of %S",
+                                 j, cComponents, bstrWriterName);
+                goto out;
+            }
+
+            if (info->bSelectable) {
+                hr = vss_ctx.pVssbc->AddComponent(idInstance, idWriter,
+                                                  info->type,
+                                                  info->bstrLogicalPath,
+                                                  info->bstrComponentName);
+                if (FAILED(hr)) {
+                    err_set(errset, hr, "failed to add component %S(%S)",
+                                     info->bstrComponentName, bstrWriterName);
+                    goto out;
+                }
+            }
+            SysFreeString(bstrWriterName);
+            bstrWriterName = NULL;
+            pComponent->FreeComponentInfo(info);
+            info = NULL;
+        }
+    }
+out:
+    if (bstrWriterName) {
+        SysFreeString(bstrWriterName);
+    }
+    if (pComponent && info) {
+        pComponent->FreeComponentInfo(info);
+    }
+}
+
+void requester_freeze(int *num_vols, ErrorSet *errset)
+{
+    COMPointer<IVssAsync> pAsync;
+    HANDLE volume;
+    HRESULT hr;
+    LONG ctx;
+    GUID guidSnapshotSet = GUID_NULL;
+    SECURITY_DESCRIPTOR sd;
+    SECURITY_ATTRIBUTES sa;
+    WCHAR short_volume_name[64], *display_name = short_volume_name;
+    DWORD wait_status;
+    int num_fixed_drives = 0, i;
+
+    if (vss_ctx.pVssbc) { /* already frozen */
+        *num_vols = 0;
+        return;
+    }
+
+    CoInitialize(NULL);
+
+    assert(pCreateVssBackupComponents != NULL);
+    hr = pCreateVssBackupComponents(&vss_ctx.pVssbc);
+    if (FAILED(hr)) {
+        err_set(errset, hr, "failed to create VSS backup components");
+        goto out;
+    }
+
+    hr = vss_ctx.pVssbc->InitializeForBackup();
+    if (FAILED(hr)) {
+        err_set(errset, hr, "failed to initialize for backup");
+        goto out;
+    }
+
+    hr = vss_ctx.pVssbc->SetBackupState(true, true, VSS_BT_FULL, false);
+    if (FAILED(hr)) {
+        err_set(errset, hr, "failed to set backup state");
+        goto out;
+    }
+
+    /*
+     * Currently writable snapshots are not supported.
+     * To prevent the final commit (which requires to write to snapshots),
+     * ATTR_NO_AUTORECOVERY and ATTR_TRANSPORTABLE are specified here.
+     */
+    ctx = VSS_CTX_APP_ROLLBACK | VSS_VOLSNAP_ATTR_TRANSPORTABLE |
+        VSS_VOLSNAP_ATTR_NO_AUTORECOVERY | VSS_VOLSNAP_ATTR_TXF_RECOVERY;
+    hr = vss_ctx.pVssbc->SetContext(ctx);
+    if (hr == (HRESULT)VSS_E_UNSUPPORTED_CONTEXT) {
+        /* Non-server version of Windows doesn't support ATTR_TRANSPORTABLE */
+        ctx &= ~VSS_VOLSNAP_ATTR_TRANSPORTABLE;
+        hr = vss_ctx.pVssbc->SetContext(ctx);
+    }
+    if (FAILED(hr)) {
+        err_set(errset, hr, "failed to set backup context");
+        goto out;
+    }
+
+    hr = vss_ctx.pVssbc->GatherWriterMetadata(pAsync.replace());
+    if (SUCCEEDED(hr)) {
+        hr = WaitForAsync(pAsync);
+    }
+    if (FAILED(hr)) {
+        err_set(errset, hr, "failed to gather writer metadata");
+        goto out;
+    }
+
+    AddComponents(errset);
+    if (err_is_set(errset)) {
+        goto out;
+    }
+
+    hr = vss_ctx.pVssbc->StartSnapshotSet(&guidSnapshotSet);
+    if (FAILED(hr)) {
+        err_set(errset, hr, "failed to start snapshot set");
+        goto out;
+    }
+
+    volume = FindFirstVolumeW(short_volume_name, sizeof(short_volume_name));
+    if (volume == INVALID_HANDLE_VALUE) {
+        err_set(errset, hr, "failed to find first volume");
+        goto out;
+    }
+    for (;;) {
+        if (GetDriveTypeW(short_volume_name) == DRIVE_FIXED) {
+            VSS_ID pid;
+            hr = vss_ctx.pVssbc->AddToSnapshotSet(short_volume_name,
+                                                  g_gProviderId, &pid);
+            if (FAILED(hr)) {
+                WCHAR volume_path_name[PATH_MAX];
+                if (GetVolumePathNamesForVolumeNameW(
+                        short_volume_name, volume_path_name,
+                        sizeof(volume_path_name), NULL) && *volume_path_name) {
+                    display_name = volume_path_name;
+                }
+                err_set(errset, hr, "failed to add %S to snapshot set",
+                                 display_name);
+                FindVolumeClose(volume);
+                goto out;
+            }
+            num_fixed_drives++;
+        }
+        if (!FindNextVolumeW(volume, short_volume_name,
+                             sizeof(short_volume_name))) {
+            FindVolumeClose(volume);
+            break;
+        }
+    }
+
+    if (num_fixed_drives == 0) {
+        goto out; /* If there is no fixed drive, just exit. */
+    }
+
+    hr = vss_ctx.pVssbc->PrepareForBackup(pAsync.replace());
+    if (SUCCEEDED(hr)) {
+        hr = WaitForAsync(pAsync);
+    }
+    if (FAILED(hr)) {
+        err_set(errset, hr, "failed to prepare for backup");
+        goto out;
+    }
+
+    hr = vss_ctx.pVssbc->GatherWriterStatus(pAsync.replace());
+    if (SUCCEEDED(hr)) {
+        hr = WaitForAsync(pAsync);
+    }
+    if (FAILED(hr)) {
+        err_set(errset, hr, "failed to gather writer status");
+        goto out;
+    }
+
+    /* Allow unrestricted access to events */
+    InitializeSecurityDescriptor(&sd, SECURITY_DESCRIPTOR_REVISION);
+    SetSecurityDescriptorDacl(&sd, TRUE, NULL, FALSE);
+    sa.nLength = sizeof(sa);
+    sa.lpSecurityDescriptor = &sd;
+    sa.bInheritHandle = FALSE;
+
+    vss_ctx.hEventFrozen = CreateEvent(&sa, TRUE, FALSE, EVENT_NAME_FROZEN);
+    if (vss_ctx.hEventFrozen == INVALID_HANDLE_VALUE) {
+        err_set(errset, GetLastError(), "failed to create event %s",
+                EVENT_NAME_FROZEN);
+        goto out;
+    }
+    vss_ctx.hEventThaw = CreateEvent(&sa, TRUE, FALSE, EVENT_NAME_THAW);
+    if (vss_ctx.hEventThaw == INVALID_HANDLE_VALUE) {
+        err_set(errset, GetLastError(), "failed to create event %s",
+                EVENT_NAME_THAW);
+        goto out;
+    }
+    vss_ctx.hEventTimeout = CreateEvent(&sa, TRUE, FALSE, EVENT_NAME_TIMEOUT);
+    if (vss_ctx.hEventTimeout == INVALID_HANDLE_VALUE) {
+        err_set(errset, GetLastError(), "failed to create event %s",
+                EVENT_NAME_TIMEOUT);
+        goto out;
+    }
+
+    /*
+     * Start VSS quiescing operations.
+     * CQGAVssProvider::CommitSnapshots will kick vss_ctx.hEventFrozen
+     * after the applications and filesystems are frozen.
+     */
+    hr = vss_ctx.pVssbc->DoSnapshotSet(&vss_ctx.pAsyncSnapshot);
+    if (FAILED(hr)) {
+        err_set(errset, hr, "failed to do snapshot set");
+        goto out;
+    }
+
+    /* Need to call QueryStatus several times to make VSS provider progress */
+    for (i = 0; i < VSS_TIMEOUT_FREEZE_MSEC/VSS_TIMEOUT_EVENT_MSEC; i++) {
+        HRESULT hr2 = vss_ctx.pAsyncSnapshot->QueryStatus(&hr, NULL);
+        if (FAILED(hr2)) {
+            err_set(errset, hr, "failed to do snapshot set");
+            goto out;
+        }
+        if (hr != VSS_S_ASYNC_PENDING) {
+            err_set(errset, E_FAIL,
+                    "DoSnapshotSet exited without Frozen event");
+            goto out;
+        }
+        wait_status = WaitForSingleObject(vss_ctx.hEventFrozen,
+                                          VSS_TIMEOUT_EVENT_MSEC);
+        if (wait_status != WAIT_TIMEOUT) {
+            break;
+        }
+    }
+    if (wait_status != WAIT_OBJECT_0) {
+        err_set(errset, E_FAIL,
+                "couldn't receive Frozen event from VSS provider");
+        goto out;
+    }
+
+    *num_vols = vss_ctx.cFrozenVols = num_fixed_drives;
+    return;
+
+out:
+    if (vss_ctx.pVssbc) {
+        vss_ctx.pVssbc->AbortBackup();
+    }
+    requester_cleanup();
+    CoUninitialize();
+}
+
+
+void requester_thaw(int *num_vols, ErrorSet *errset)
+{
+    COMPointer<IVssAsync> pAsync;
+
+    if (vss_ctx.hEventThaw == INVALID_HANDLE_VALUE) {
+        /*
+         * In this case, DoSnapshotSet is aborted or not started,
+         * and no volumes must be frozen. We return without an error.
+         */
+        *num_vols = 0;
+        return;
+    }
+
+    /* Tell the provider that the snapshot is finished. */
+    SetEvent(vss_ctx.hEventThaw);
+
+    assert(vss_ctx.pVssbc);
+    assert(vss_ctx.pAsyncSnapshot);
+
+    HRESULT hr = WaitForAsync(vss_ctx.pAsyncSnapshot);
+    switch (hr) {
+    case VSS_S_ASYNC_FINISHED:
+        hr = vss_ctx.pVssbc->BackupComplete(pAsync.replace());
+        if (SUCCEEDED(hr)) {
+            hr = WaitForAsync(pAsync);
+        }
+        if (FAILED(hr)) {
+            err_set(errset, hr, "failed to complete backup");
+        }
+        break;
+
+    case (HRESULT)VSS_E_OBJECT_NOT_FOUND:
+        /*
+         * On Windows earlier than 2008 SP2 which does not support
+         * VSS_VOLSNAP_ATTR_NO_AUTORECOVERY context, the final commit is not
+         * skipped and VSS is aborted by VSS_E_OBJECT_NOT_FOUND. However, as
+         * the system had been frozen until fsfreeze-thaw command was issued,
+         * we ignore this error.
+         */
+        vss_ctx.pVssbc->AbortBackup();
+        break;
+
+    case VSS_E_UNEXPECTED_PROVIDER_ERROR:
+        if (WaitForSingleObject(vss_ctx.hEventTimeout, 0) != WAIT_OBJECT_0) {
+            err_set(errset, hr, "unexpected error in VSS provider");
+            break;
+        }
+        /* fall through if hEventTimeout is signaled */
+
+    case (HRESULT)VSS_E_HOLD_WRITES_TIMEOUT:
+        err_set(errset, hr, "couldn't hold writes: "
+                "fsfreeze is limited up to 10 seconds");
+        break;
+
+    default:
+        err_set(errset, hr, "failed to do snapshot set");
+    }
+
+    if (err_is_set(errset)) {
+        vss_ctx.pVssbc->AbortBackup();
+    }
+    *num_vols = vss_ctx.cFrozenVols;
+    requester_cleanup();
+
+    CoUninitialize();
+}
diff --git a/qga/vss-win32/requester.h b/qga/vss-win32/requester.h
new file mode 100644
index 0000000000..cffec01791
--- /dev/null
+++ b/qga/vss-win32/requester.h
@@ -0,0 +1,42 @@
+/*
+ * QEMU Guest Agent VSS requester declarations
+ *
+ * Copyright Hitachi Data Systems Corp. 2013
+ *
+ * Authors:
+ *  Tomoki Sekiyama   <tomoki.sekiyama@hds.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#ifndef VSS_WIN32_REQUESTER_H
+#define VSS_WIN32_REQUESTER_H
+
+#include "qemu/compiler.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* Callback to set Error; used to avoid linking glib to the DLL */
+typedef void (*ErrorSetFunc)(void **errp, int win32_err, int err_class,
+                             const char *fmt, ...) GCC_FMT_ATTR(4, 5);
+typedef struct ErrorSet {
+    ErrorSetFunc error_set;
+    void **errp;
+    int err_class;
+} ErrorSet;
+
+STDAPI requester_init(void);
+STDAPI requester_deinit(void);
+
+typedef void (*QGAVSSRequesterFunc)(int *, ErrorSet *);
+void requester_freeze(int *num_vols, ErrorSet *errset);
+void requester_thaw(int *num_vols, ErrorSet *errset);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
diff --git a/qga/vss-win32/vss-common.h b/qga/vss-win32/vss-common.h
new file mode 100644
index 0000000000..ce14e14290
--- /dev/null
+++ b/qga/vss-win32/vss-common.h
@@ -0,0 +1,129 @@
+/*
+ * QEMU Guest Agent win32 VSS common declarations
+ *
+ * Copyright Hitachi Data Systems Corp. 2013
+ *
+ * Authors:
+ *  Tomoki Sekiyama   <tomoki.sekiyama@hds.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#ifndef VSS_WIN32_H
+#define VSS_WIN32_H
+
+#define __MIDL_user_allocate_free_DEFINED__
+#include "config-host.h"
+#include <windows.h>
+#include <shlwapi.h>
+
+/* Reduce warnings to include vss.h */
+
+/* Ignore annotations for MS IDE */
+#define __in  IN
+#define __out OUT
+#define __RPC_unique_pointer
+#define __RPC_string
+#define __RPC__deref_inout_opt
+#define __RPC__out
+#ifndef __RPC__out_ecount_part
+#define __RPC__out_ecount_part(x, y)
+#endif
+#define _declspec(x)
+#undef uuid
+#define uuid(x)
+
+/* Undef some duplicated error codes redefined in vss.h */
+#undef VSS_E_BAD_STATE
+#undef VSS_E_PROVIDER_NOT_REGISTERED
+#undef VSS_E_PROVIDER_VETO
+#undef VSS_E_OBJECT_NOT_FOUND
+#undef VSS_E_VOLUME_NOT_SUPPORTED
+#undef VSS_E_VOLUME_NOT_SUPPORTED_BY_PROVIDER
+#undef VSS_E_OBJECT_ALREADY_EXISTS
+#undef VSS_E_UNEXPECTED_PROVIDER_ERROR
+#undef VSS_E_INVALID_XML_DOCUMENT
+#undef VSS_E_MAXIMUM_NUMBER_OF_VOLUMES_REACHED
+#undef VSS_E_MAXIMUM_NUMBER_OF_SNAPSHOTS_REACHED
+
+/*
+ * VSS headers must be installed from Microsoft VSS SDK 7.2 available at:
+ * http://www.microsoft.com/en-us/download/details.aspx?id=23490
+ */
+#include "inc/win2003/vss.h"
+
+/* Macros to convert char definitions to wchar */
+#define _L(a) L##a
+#define L(a) _L(a)
+
+/* Constants for QGA VSS Provider */
+
+#define QGA_PROVIDER_NAME "QEMU Guest Agent VSS Provider"
+#define QGA_PROVIDER_LNAME L(QGA_PROVIDER_NAME)
+#define QGA_PROVIDER_VERSION L(QEMU_VERSION)
+
+#define EVENT_NAME_FROZEN  "Global\\QGAVSSEvent-frozen"
+#define EVENT_NAME_THAW    "Global\\QGAVSSEvent-thaw"
+#define EVENT_NAME_TIMEOUT "Global\\QGAVSSEvent-timeout"
+
+const GUID g_gProviderId = { 0x3629d4ed, 0xee09, 0x4e0e,
+    {0x9a, 0x5c, 0x6d, 0x8b, 0xa2, 0x87, 0x2a, 0xef} };
+const GUID g_gProviderVersion = { 0x11ef8b15, 0xcac6, 0x40d6,
+    {0x8d, 0x5c, 0x8f, 0xfc, 0x16, 0x3f, 0x24, 0xca} };
+
+const CLSID CLSID_QGAVSSProvider = { 0x6e6a3492, 0x8d4d, 0x440c,
+    {0x96, 0x19, 0x5e, 0x5d, 0x0c, 0xc3, 0x1c, 0xa8} };
+
+const TCHAR g_szClsid[] = TEXT("{6E6A3492-8D4D-440C-9619-5E5D0CC31CA8}");
+const TCHAR g_szProgid[] = TEXT("QGAVSSProvider");
+
+/* Enums undefined in VSS SDK 7.2 but defined in newer Windows SDK */
+enum __VSS_VOLUME_SNAPSHOT_ATTRIBUTES {
+    VSS_VOLSNAP_ATTR_NO_AUTORECOVERY       = 0x00000002,
+    VSS_VOLSNAP_ATTR_TXF_RECOVERY          = 0x02000000
+};
+
+
+/* COM pointer utility; call ->Release() when it goes out of scope */
+template <class T>
+class COMPointer {
+    COMPointer(const COMPointer<T> &p) { } /* no copy */
+    T *p;
+public:
+    COMPointer &operator=(T *new_p)
+    {
+        /* Assignment of a new T* (or NULL) causes release of previous p */
+        if (p && p != new_p) {
+            p->Release();
+        }
+        p = new_p;
+        return *this;
+    }
+    /* Replace by assignment to the pointer of p  */
+    T **replace(void)
+    {
+        *this = NULL;
+        return &p;
+    }
+    /* Make COMPointer be used like T* */
+    operator T*() { return p; }
+    T *operator->(void) { return p; }
+    T &operator*(void) { return *p; }
+    operator bool() { return !!p; }
+
+    COMPointer(T *p = NULL) : p(p) { }
+    ~COMPointer() { *this = NULL; }  /* Automatic release */
+};
+
+/*
+ * COM initializer; this should declared before COMPointer to uninitialize COM
+ * after releasing COM objects.
+ */
+class COMInitializer {
+public:
+    COMInitializer() { CoInitialize(NULL); }
+    ~COMInitializer() { CoUninitialize(); }
+};
+
+#endif