Merge remote-tracking branch 'remotes/mdroth/tags/qga-pull-2018-10-30-v3-tag' into staging

qemu-ga patch queue for soft-freeze

* support for --retry-path option for recovering from communication
  path failures
* support for serial/device name in guest-get-fsinfo for linux/w32
* support for freezing individual mount points in guest-fsfreeze-*
* fixes for unicode paths on w32, not-present vcpus in guest-get-vcpus,
  buffer overflow in guest-get-fsinfo for w32, and other minor fixes

v3:
* remove redundant check for --static in configure
* correct authorship on "qga-win: add debugging information"

v2:
* set libudev=off in configure for static builds

# gpg: Signature made Wed 31 Oct 2018 14:13:58 GMT
# gpg:                using RSA key 3353C9CEF108B584
# gpg: Good signature from "Michael Roth <flukshun@gmail.com>"
# gpg:                 aka "Michael Roth <mdroth@utexas.edu>"
# gpg:                 aka "Michael Roth <mdroth@linux.vnet.ibm.com>"
# Primary key fingerprint: CEAC C9E1 5534 EBAB B82D  3FA0 3353 C9CE F108 B584

* remotes/mdroth/tags/qga-pull-2018-10-30-v3-tag: (24 commits)
  qga-win: changing --retry-path option behavior
  qga-win: report specific error when failing to open channel
  qga-win: install service with --retry-path set by default
  qga: add --retry-path option for re-initializing channel on failure
  qga: move w32 service handling out of run_agent()
  qga: hang GAConfig/socket_activation off of GAState global
  qga: group agent init/cleanup init separate routines
  qga: fix an off-by-one issue
  qga-win: demystify namespace stripping
  qga-win: return disk device in guest-get-fsinfo
  qga-win: handle multi-disk volumes
  qga-win: refactor disk info
  qga-win: report disk serial number
  qga-win: refactor disk properties (bus)
  qga-win: add debugging information
  build: rename CONFIG_QGA_NTDDDISK to CONFIG_QGA_NTDDSCSI
  qga-win: fsinfo: pci-info: allow partial info
  qga-win: prevent crash when executing fsinfo command
  qga: linux: return disk device in guest-get-fsinfo
  qga: linux: report disk serial number
  ...

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

13 files changed, 686 insertions, 210 deletions

diff --git a/configure b/configure
index 743e12f22c..46ae1e8c76 100755
--- a/configure
+++ b/configure
@@ -474,6 +474,7 @@ libxml2=""
 docker="no"
 debug_mutex="no"
 libpmem=""
+libudev="no"
 
 # cross compilers defaults, can be overridden with --cross-cc-ARCH
 cross_cc_aarch64="aarch64-linux-gnu-gcc"
@@ -870,6 +871,7 @@ Linux)
   vhost_vsock="yes"
   QEMU_INCLUDES="-I\$(SRC_PATH)/linux-headers -I$(pwd)/linux-headers $QEMU_INCLUDES"
   supported_os="yes"
+  libudev="yes"
 ;;
 esac
 
@@ -5609,6 +5611,17 @@ if test "$libnfs" != "no" ; then
   fi
 fi
 
+##########################################
+# Do we have libudev
+if test "$libudev" != "no" ; then
+  if $pkg_config libudev && test "$static" != "yes"; then
+    libudev="yes"
+    libudev_libs=$($pkg_config --libs libudev)
+  else
+    libudev="no"
+  fi
+fi
+
 # Now we've finished running tests it's OK to add -Werror to the compiler flags
 if test "$werror" = "yes"; then
     QEMU_CFLAGS="-Werror $QEMU_CFLAGS"
@@ -6033,6 +6046,7 @@ echo "VxHS block device $vxhs"
 echo "capstone          $capstone"
 echo "docker            $docker"
 echo "libpmem support   $libpmem"
+echo "libudev           $libudev"
 
 if test "$sdl_too_old" = "yes"; then
 echo "-> Your SDL version is too old - please upgrade to have SDL support"
@@ -6128,7 +6142,7 @@ if test "$mingw32" = "yes" ; then
     echo "WIN_SDK=\"$win_sdk\"" >> $config_host_mak
   fi
   if test "$guest_agent_ntddscsi" = "yes" ; then
-    echo "CONFIG_QGA_NTDDDISK=y" >> $config_host_mak
+    echo "CONFIG_QGA_NTDDSCSI=y" >> $config_host_mak
   fi
   if test "$guest_agent_msi" = "yes"; then
     echo "QEMU_GA_MSI_ENABLED=yes" >> $config_host_mak
@@ -6868,6 +6882,11 @@ if test "$docker" != "no"; then
     echo "HAVE_USER_DOCKER=y" >> $config_host_mak
 fi
 
+if test "$libudev" != "no"; then
+    echo "CONFIG_LIBUDEV=y" >> $config_host_mak
+    echo "LIBUDEV_LIBS=$libudev_libs" >> $config_host_mak
+fi
+
 # use included Linux headers
 if test "$linux" = "yes" ; then
   mkdir -p linux-headers
diff --git a/qga/Makefile.objs b/qga/Makefile.objs
index ed08c5917c..80e6bb3c2e 100644
--- a/qga/Makefile.objs
+++ b/qga/Makefile.objs
@@ -1,3 +1,4 @@
+commands-posix.o-libs := $(LIBUDEV_LIBS)
 qga-obj-y = commands.o guest-agent-command-state.o main.o
 qga-obj-$(CONFIG_POSIX) += commands-posix.o channel-posix.o
 qga-obj-$(CONFIG_WIN32) += commands-win32.o channel-win32.o service-win32.o
diff --git a/qga/channel-win32.c b/qga/channel-win32.c
index b3597a8a0f..c86f4388db 100644
--- a/qga/channel-win32.c
+++ b/qga/channel-win32.c
@@ -302,7 +302,8 @@ static gboolean ga_channel_open(GAChannel *c, GAChannelMethod method,
                            OPEN_EXISTING,
                            FILE_FLAG_NO_BUFFERING | FILE_FLAG_OVERLAPPED, NULL);
     if (c->handle == INVALID_HANDLE_VALUE) {
-        g_critical("error opening path %s", newpath);
+        g_critical("error opening path %s: %s", newpath,
+                   g_win32_error_message(GetLastError()));
         return false;
     }
 
diff --git a/qga/commands-posix.c b/qga/commands-posix.c
index 37e8a2d791..1877976522 100644
--- a/qga/commands-posix.c
+++ b/qga/commands-posix.c
@@ -48,6 +48,10 @@ extern char **environ;
 #include <net/if.h>
 #include <sys/statvfs.h>
 
+#ifdef CONFIG_LIBUDEV
+#include <libudev.h>
+#endif
+
 #ifdef FIFREEZE
 #define CONFIG_FSFREEZE
 #endif
@@ -872,6 +876,10 @@ static void build_guest_fsinfo_for_real_device(char const *syspath,
     GuestDiskAddressList *list = NULL;
     bool has_ata = false, has_host = false, has_tgt = false;
     char *p, *q, *driver = NULL;
+#ifdef CONFIG_LIBUDEV
+    struct udev *udev = NULL;
+    struct udev_device *udevice = NULL;
+#endif
 
     p = strstr(syspath, "/devices/pci");
     if (!p || sscanf(p + 12, "%*x:%*x/%x:%x:%x.%x%n",
@@ -936,6 +944,26 @@ static void build_guest_fsinfo_for_real_device(char const *syspath,
     list = g_malloc0(sizeof(*list));
     list->value = disk;
 
+#ifdef CONFIG_LIBUDEV
+    udev = udev_new();
+    udevice = udev_device_new_from_syspath(udev, syspath);
+    if (udev == NULL || udevice == NULL) {
+        g_debug("failed to query udev");
+    } else {
+        const char *devnode, *serial;
+        devnode = udev_device_get_devnode(udevice);
+        if (devnode != NULL) {
+            disk->dev = g_strdup(devnode);
+            disk->has_dev = true;
+        }
+        serial = udev_device_get_property_value(udevice, "ID_SERIAL");
+        if (serial != NULL && *serial != 0) {
+            disk->serial = g_strdup(serial);
+            disk->has_serial = true;
+        }
+    }
+#endif
+
     if (strcmp(driver, "ata_piix") == 0) {
         /* a host per ide bus, target*:0:<unit>:0 */
         if (!has_host || !has_tgt) {
@@ -995,14 +1023,19 @@ static void build_guest_fsinfo_for_real_device(char const *syspath,
 
     list->next = fs->disk;
     fs->disk = list;
-    g_free(driver);
-    return;
+    goto out;
 
 cleanup:
     if (list) {
         qapi_free_GuestDiskAddressList(list);
     }
+out:
     g_free(driver);
+#ifdef CONFIG_LIBUDEV
+    udev_unref(udev);
+    udev_device_unref(udevice);
+#endif
+    return;
 }
 
 static void build_guest_fsinfo_for_device(char const *devpath,
@@ -2035,61 +2068,56 @@ static long sysconf_exact(int name, const char *name_str, Error **errp)
  * Written members remain unmodified on error.
  */
 static void transfer_vcpu(GuestLogicalProcessor *vcpu, bool sys2vcpu,
-                          Error **errp)
+                          char *dirpath, Error **errp)
 {
-    char *dirpath;
+    int fd;
+    int res;
     int dirfd;
+    static const char fn[] = "online";
 
-    dirpath = g_strdup_printf("/sys/devices/system/cpu/cpu%" PRId64 "/",
-                              vcpu->logical_id);
     dirfd = open(dirpath, O_RDONLY | O_DIRECTORY);
     if (dirfd == -1) {
         error_setg_errno(errp, errno, "open(\"%s\")", dirpath);
-    } else {
-        static const char fn[] = "online";
-        int fd;
-        int res;
-
-        fd = openat(dirfd, fn, sys2vcpu ? O_RDONLY : O_RDWR);
-        if (fd == -1) {
-            if (errno != ENOENT) {
-                error_setg_errno(errp, errno, "open(\"%s/%s\")", dirpath, fn);
-            } else if (sys2vcpu) {
-                vcpu->online = true;
-                vcpu->can_offline = false;
-            } else if (!vcpu->online) {
-                error_setg(errp, "logical processor #%" PRId64 " can't be "
-                           "offlined", vcpu->logical_id);
-            } /* otherwise pretend successful re-onlining */
-        } else {
-            unsigned char status;
-
-            res = pread(fd, &status, 1, 0);
-            if (res == -1) {
-                error_setg_errno(errp, errno, "pread(\"%s/%s\")", dirpath, fn);
-            } else if (res == 0) {
-                error_setg(errp, "pread(\"%s/%s\"): unexpected EOF", dirpath,
-                           fn);
-            } else if (sys2vcpu) {
-                vcpu->online = (status != '0');
-                vcpu->can_offline = true;
-            } else if (vcpu->online != (status != '0')) {
-                status = '0' + vcpu->online;
-                if (pwrite(fd, &status, 1, 0) == -1) {
-                    error_setg_errno(errp, errno, "pwrite(\"%s/%s\")", dirpath,
-                                     fn);
-                }
-            } /* otherwise pretend successful re-(on|off)-lining */
+        return;
+    }
 
-            res = close(fd);
-            g_assert(res == 0);
-        }
+    fd = openat(dirfd, fn, sys2vcpu ? O_RDONLY : O_RDWR);
+    if (fd == -1) {
+        if (errno != ENOENT) {
+            error_setg_errno(errp, errno, "open(\"%s/%s\")", dirpath, fn);
+        } else if (sys2vcpu) {
+            vcpu->online = true;
+            vcpu->can_offline = false;
+        } else if (!vcpu->online) {
+            error_setg(errp, "logical processor #%" PRId64 " can't be "
+                       "offlined", vcpu->logical_id);
+        } /* otherwise pretend successful re-onlining */
+    } else {
+        unsigned char status;
+
+        res = pread(fd, &status, 1, 0);
+        if (res == -1) {
+            error_setg_errno(errp, errno, "pread(\"%s/%s\")", dirpath, fn);
+        } else if (res == 0) {
+            error_setg(errp, "pread(\"%s/%s\"): unexpected EOF", dirpath,
+                       fn);
+        } else if (sys2vcpu) {
+            vcpu->online = (status != '0');
+            vcpu->can_offline = true;
+        } else if (vcpu->online != (status != '0')) {
+            status = '0' + vcpu->online;
+            if (pwrite(fd, &status, 1, 0) == -1) {
+                error_setg_errno(errp, errno, "pwrite(\"%s/%s\")", dirpath,
+                                 fn);
+            }
+        } /* otherwise pretend successful re-(on|off)-lining */
 
-        res = close(dirfd);
+        res = close(fd);
         g_assert(res == 0);
     }
 
-    g_free(dirpath);
+    res = close(dirfd);
+    g_assert(res == 0);
 }
 
 GuestLogicalProcessorList *qmp_guest_get_vcpus(Error **errp)
@@ -2107,17 +2135,21 @@ GuestLogicalProcessorList *qmp_guest_get_vcpus(Error **errp)
     while (local_err == NULL && current < sc_max) {
         GuestLogicalProcessor *vcpu;
         GuestLogicalProcessorList *entry;
-
-        vcpu = g_malloc0(sizeof *vcpu);
-        vcpu->logical_id = current++;
-        vcpu->has_can_offline = true; /* lolspeak ftw */
-        transfer_vcpu(vcpu, true, &local_err);
-
-        entry = g_malloc0(sizeof *entry);
-        entry->value = vcpu;
-
-        *link = entry;
-        link = &entry->next;
+        int64_t id = current++;
+        char *path = g_strdup_printf("/sys/devices/system/cpu/cpu%" PRId64 "/",
+                                     id);
+
+        if (g_file_test(path, G_FILE_TEST_EXISTS)) {
+            vcpu = g_malloc0(sizeof *vcpu);
+            vcpu->logical_id = id;
+            vcpu->has_can_offline = true; /* lolspeak ftw */
+            transfer_vcpu(vcpu, true, path, &local_err);
+            entry = g_malloc0(sizeof *entry);
+            entry->value = vcpu;
+            *link = entry;
+            link = &entry->next;
+        }
+        g_free(path);
     }
 
     if (local_err == NULL) {
@@ -2138,7 +2170,11 @@ int64_t qmp_guest_set_vcpus(GuestLogicalProcessorList *vcpus, Error **errp)
 
     processed = 0;
     while (vcpus != NULL) {
-        transfer_vcpu(vcpus->value, false, &local_err);
+        char *path = g_strdup_printf("/sys/devices/system/cpu/cpu%" PRId64 "/",
+                                     vcpus->value->logical_id);
+
+        transfer_vcpu(vcpus->value, false, path, &local_err);
+        g_free(path);
         if (local_err != NULL) {
             break;
         }
diff --git a/qga/commands-win32.c b/qga/commands-win32.c
index 98d9735389..ef1d7d48d2 100644
--- a/qga/commands-win32.c
+++ b/qga/commands-win32.c
@@ -89,6 +89,12 @@ static OpenFlags guest_file_open_modes[] = {
     {"a+b", FILE_GENERIC_APPEND|GENERIC_READ, OPEN_ALWAYS  }
 };
 
+#define debug_error(msg) do { \
+    char *suffix = g_win32_error_message(GetLastError()); \
+    g_debug("%s: %s", (msg), suffix); \
+    g_free(suffix); \
+} while (0)
+
 static OpenFlags *find_open_flag(const char *mode_str)
 {
     int mode;
@@ -160,13 +166,15 @@ static void handle_set_nonblocking(HANDLE fh)
 int64_t qmp_guest_file_open(const char *path, bool has_mode,
                             const char *mode, Error **errp)
 {
-    int64_t fd;
+    int64_t fd = -1;
     HANDLE fh;
     HANDLE templ_file = NULL;
     DWORD share_mode = FILE_SHARE_READ;
     DWORD flags_and_attr = FILE_ATTRIBUTE_NORMAL;
     LPSECURITY_ATTRIBUTES sa_attr = NULL;
     OpenFlags *guest_flags;
+    GError *gerr = NULL;
+    wchar_t *w_path = NULL;
 
     if (!has_mode) {
         mode = "r";
@@ -175,16 +183,21 @@ int64_t qmp_guest_file_open(const char *path, bool has_mode,
     guest_flags = find_open_flag(mode);
     if (guest_flags == NULL) {
         error_setg(errp, "invalid file open mode");
-        return -1;
+        goto done;
     }
 
-    fh = CreateFile(path, guest_flags->desired_access, share_mode, sa_attr,
+    w_path = g_utf8_to_utf16(path, -1, NULL, NULL, &gerr);
+    if (!w_path) {
+        goto done;
+    }
+
+    fh = CreateFileW(w_path, guest_flags->desired_access, share_mode, sa_attr,
                     guest_flags->creation_disposition, flags_and_attr,
                     templ_file);
     if (fh == INVALID_HANDLE_VALUE) {
         error_setg_win32(errp, GetLastError(), "failed to open file '%s'",
                          path);
-        return -1;
+        goto done;
     }
 
     /* set fd non-blocking to avoid common use cases (like reading from a
@@ -196,10 +209,17 @@ int64_t qmp_guest_file_open(const char *path, bool has_mode,
     if (fd < 0) {
         CloseHandle(fh);
         error_setg(errp, "failed to add handle to qmp handle table");
-        return -1;
+        goto done;
     }
 
     slog("guest-file-open, handle: % " PRId64, fd);
+
+done:
+    if (gerr) {
+        error_setg(errp, QERR_QGA_COMMAND_FAILED, gerr->message);
+        g_error_free(gerr);
+    }
+    g_free(w_path);
     return fd;
 }
 
@@ -465,15 +485,32 @@ static STORAGE_BUS_TYPE win2qemu[] = {
 
 static GuestDiskBusType find_bus_type(STORAGE_BUS_TYPE bus)
 {
-    if (bus > ARRAY_SIZE(win2qemu) || (int)bus < 0) {
+    if (bus >= ARRAY_SIZE(win2qemu) || (int)bus < 0) {
         return GUEST_DISK_BUS_TYPE_UNKNOWN;
     }
     return win2qemu[(int)bus];
 }
 
+/* XXX: The following function is BROKEN!
+ *
+ * It does not work and probably has never worked. When we query for list of
+ * disks we get cryptic names like "\Device\0000001d" instead of
+ * "\PhysicalDriveX" or "\HarddiskX". Whether the names can be translated one
+ * way or the other for comparison is an open question.
+ *
+ * When we query volume names (the original version) we are able to match those
+ * but then the property queries report error "Invalid function". (duh!)
+ */
+
+/*
 DEFINE_GUID(GUID_DEVINTERFACE_VOLUME,
         0x53f5630dL, 0xb6bf, 0x11d0, 0x94, 0xf2,
         0x00, 0xa0, 0xc9, 0x1e, 0xfb, 0x8b);
+*/
+DEFINE_GUID(GUID_DEVINTERFACE_DISK,
+        0x53f56307L, 0xb6bf, 0x11d0, 0x94, 0xf2,
+        0x00, 0xa0, 0xc9, 0x1e, 0xfb, 0x8b);
+
 
 static GuestPCIAddress *get_pci_info(char *guid, Error **errp)
 {
@@ -484,23 +521,38 @@ static GuestPCIAddress *get_pci_info(char *guid, Error **errp)
     char dev_name[MAX_PATH];
     char *buffer = NULL;
     GuestPCIAddress *pci = NULL;
-    char *name = g_strdup(&guid[4]);
+    char *name = NULL;
+    bool partial_pci = false;
+    pci = g_malloc0(sizeof(*pci));
+    pci->domain = -1;
+    pci->slot = -1;
+    pci->function = -1;
+    pci->bus = -1;
+
+    if (g_str_has_prefix(guid, "\\\\.\\") ||
+        g_str_has_prefix(guid, "\\\\?\\")) {
+        name = g_strdup(guid + 4);
+    } else {
+        name = g_strdup(guid);
+    }
 
     if (!QueryDosDevice(name, dev_name, ARRAY_SIZE(dev_name))) {
         error_setg_win32(errp, GetLastError(), "failed to get dos device name");
         goto out;
     }
 
-    dev_info = SetupDiGetClassDevs(&GUID_DEVINTERFACE_VOLUME, 0, 0,
+    dev_info = SetupDiGetClassDevs(&GUID_DEVINTERFACE_DISK, 0, 0,
                                    DIGCF_PRESENT | DIGCF_DEVICEINTERFACE);
     if (dev_info == INVALID_HANDLE_VALUE) {
         error_setg_win32(errp, GetLastError(), "failed to get devices tree");
         goto out;
     }
 
+    g_debug("enumerating devices");
     dev_info_data.cbSize = sizeof(SP_DEVINFO_DATA);
     for (i = 0; SetupDiEnumDeviceInfo(dev_info, i, &dev_info_data); i++) {
-        DWORD addr, bus, slot, func, dev, data, size2;
+        DWORD addr, bus, slot, data, size2;
+        int func, dev;
         while (!SetupDiGetDeviceRegistryProperty(dev_info, &dev_info_data,
                                             SPDRP_PHYSICAL_DEVICE_OBJECT_NAME,
                                             &data, (PBYTE)buffer, size,
@@ -522,6 +574,7 @@ static GuestPCIAddress *get_pci_info(char *guid, Error **errp)
         if (g_strcmp0(buffer, dev_name)) {
             continue;
         }
+        g_debug("found device %s", dev_name);
 
         /* There is no need to allocate buffer in the next functions. The size
          * is known and ULONG according to
@@ -530,21 +583,27 @@ static GuestPCIAddress *get_pci_info(char *guid, Error **errp)
          */
         if (!SetupDiGetDeviceRegistryProperty(dev_info, &dev_info_data,
                    SPDRP_BUSNUMBER, &data, (PBYTE)&bus, size, NULL)) {
-            break;
+            debug_error("failed to get bus");
+            bus = -1;
+            partial_pci = true;
         }
 
         /* The function retrieves the device's address. This value will be
          * transformed into device function and number */
         if (!SetupDiGetDeviceRegistryProperty(dev_info, &dev_info_data,
                    SPDRP_ADDRESS, &data, (PBYTE)&addr, size, NULL)) {
-            break;
+            debug_error("failed to get address");
+            addr = -1;
+            partial_pci = true;
         }
 
         /* This call returns UINumber of DEVICE_CAPABILITIES structure.
          * This number is typically a user-perceived slot number. */
         if (!SetupDiGetDeviceRegistryProperty(dev_info, &dev_info_data,
                    SPDRP_UI_NUMBER, &data, (PBYTE)&slot, size, NULL)) {
-            break;
+            debug_error("failed to get slot");
+            slot = -1;
+            partial_pci = true;
         }
 
         /* SetupApi gives us the same information as driver with
@@ -554,13 +613,19 @@ static GuestPCIAddress *get_pci_info(char *guid, Error **errp)
          * DeviceNumber = (USHORT)(((propertyAddress) >> 16) & 0x0000FFFF);
          * SPDRP_ADDRESS is propertyAddress, so we do the same.*/
 
-        func = addr & 0x0000FFFF;
-        dev = (addr >> 16) & 0x0000FFFF;
-        pci = g_malloc0(sizeof(*pci));
-        pci->domain = dev;
-        pci->slot = slot;
-        pci->function = func;
-        pci->bus = bus;
+        if (partial_pci) {
+            pci->domain = -1;
+            pci->slot = -1;
+            pci->function = -1;
+            pci->bus = -1;
+        } else {
+            func = ((int) addr == -1) ? -1 : addr & 0x0000FFFF;
+            dev = ((int) addr == -1) ? -1 : (addr >> 16) & 0x0000FFFF;
+            pci->domain = dev;
+            pci->slot = (int) slot;
+            pci->function = func;
+            pci->bus = (int) bus;
+        }
         break;
     }
 
@@ -572,85 +637,228 @@ out:
     return pci;
 }
 
-static int get_disk_bus_type(HANDLE vol_h, Error **errp)
+static void get_disk_properties(HANDLE vol_h, GuestDiskAddress *disk,
+    Error **errp)
 {
     STORAGE_PROPERTY_QUERY query;
     STORAGE_DEVICE_DESCRIPTOR *dev_desc, buf;
     DWORD received;
+    ULONG size = sizeof(buf);
 
     dev_desc = &buf;
-    dev_desc->Size = sizeof(buf);
     query.PropertyId = StorageDeviceProperty;
     query.QueryType = PropertyStandardQuery;
 
     if (!DeviceIoControl(vol_h, IOCTL_STORAGE_QUERY_PROPERTY, &query,
                          sizeof(STORAGE_PROPERTY_QUERY), dev_desc,
-                         dev_desc->Size, &received, NULL)) {
+                         size, &received, NULL)) {
         error_setg_win32(errp, GetLastError(), "failed to get bus type");
-        return -1;
+        return;
+    }
+    disk->bus_type = find_bus_type(dev_desc->BusType);
+    g_debug("bus type %d", disk->bus_type);
+
+    /* Query once more. Now with long enough buffer. */
+    size = dev_desc->Size;
+    dev_desc = g_malloc0(size);
+    if (!DeviceIoControl(vol_h, IOCTL_STORAGE_QUERY_PROPERTY, &query,
+                         sizeof(STORAGE_PROPERTY_QUERY), dev_desc,
+                         size, &received, NULL)) {
+        error_setg_win32(errp, GetLastError(), "failed to get serial number");
+        g_debug("failed to get serial number");
+        goto out_free;
     }
+    if (dev_desc->SerialNumberOffset > 0) {
+        const char *serial;
+        size_t len;
 
-    return dev_desc->BusType;
+        if (dev_desc->SerialNumberOffset >= received) {
+            error_setg(errp, "failed to get serial number: offset outside the buffer");
+            g_debug("serial number offset outside the buffer");
+            goto out_free;
+        }
+        serial = (char *)dev_desc + dev_desc->SerialNumberOffset;
+        len = received - dev_desc->SerialNumberOffset;
+        g_debug("serial number \"%s\"", serial);
+        if (*serial != 0) {
+            disk->serial = g_strndup(serial, len);
+            disk->has_serial = true;
+        }
+    }
+out_free:
+    g_free(dev_desc);
+
+    return;
 }
 
-/* VSS provider works with volumes, thus there is no difference if
- * the volume consist of spanned disks. Info about the first disk in the
- * volume is returned for the spanned disk group (LVM) */
-static GuestDiskAddressList *build_guest_disk_info(char *guid, Error **errp)
+static void get_single_disk_info(GuestDiskAddress *disk, Error **errp)
 {
-    GuestDiskAddressList *list = NULL;
-    GuestDiskAddress *disk;
     SCSI_ADDRESS addr, *scsi_ad;
     DWORD len;
-    int bus;
-    HANDLE vol_h;
+    HANDLE disk_h;
+    Error *local_err = NULL;
 
     scsi_ad = &addr;
-    char *name = g_strndup(guid, strlen(guid)-1);
 
-    vol_h = CreateFile(name, 0, FILE_SHARE_READ, NULL, OPEN_EXISTING,
+    g_debug("getting disk info for: %s", disk->dev);
+    disk_h = CreateFile(disk->dev, 0, FILE_SHARE_READ, NULL, OPEN_EXISTING,
                        0, NULL);
-    if (vol_h == INVALID_HANDLE_VALUE) {
-        error_setg_win32(errp, GetLastError(), "failed to open volume");
-        goto out_free;
+    if (disk_h == INVALID_HANDLE_VALUE) {
+        error_setg_win32(errp, GetLastError(), "failed to open disk");
+        return;
     }
 
-    bus = get_disk_bus_type(vol_h, errp);
-    if (bus < 0) {
-        goto out_close;
+    get_disk_properties(disk_h, disk, &local_err);
+    if (local_err) {
+        error_propagate(errp, local_err);
+        goto err_close;
     }
 
-    disk = g_malloc0(sizeof(*disk));
-    disk->bus_type = find_bus_type(bus);
-    if (bus == BusTypeScsi || bus == BusTypeAta || bus == BusTypeRAID
+    g_debug("bus type %d", disk->bus_type);
+    /* always set pci_controller as required by schema. get_pci_info() should
+     * report -1 values for non-PCI buses rather than fail. fail the command
+     * if that doesn't hold since that suggests some other unexpected
+     * breakage
+     */
+    disk->pci_controller = get_pci_info(disk->dev, &local_err);
+    if (local_err) {
+        error_propagate(errp, local_err);
+        goto err_close;
+    }
+    if (disk->bus_type == GUEST_DISK_BUS_TYPE_SCSI
+            || disk->bus_type == GUEST_DISK_BUS_TYPE_IDE
+            || disk->bus_type == GUEST_DISK_BUS_TYPE_RAID
 #if (_WIN32_WINNT >= 0x0600)
             /* This bus type is not supported before Windows Server 2003 SP1 */
-            || bus == BusTypeSas
+            || disk->bus_type == GUEST_DISK_BUS_TYPE_SAS
 #endif
         ) {
         /* We are able to use the same ioctls for different bus types
          * according to Microsoft docs
          * https://technet.microsoft.com/en-us/library/ee851589(v=ws.10).aspx */
-        if (DeviceIoControl(vol_h, IOCTL_SCSI_GET_ADDRESS, NULL, 0, scsi_ad,
+        g_debug("getting pci-controller info");
+        if (DeviceIoControl(disk_h, IOCTL_SCSI_GET_ADDRESS, NULL, 0, scsi_ad,
                             sizeof(SCSI_ADDRESS), &len, NULL)) {
             disk->unit = addr.Lun;
             disk->target = addr.TargetId;
             disk->bus = addr.PathId;
-            disk->pci_controller = get_pci_info(name, errp);
         }
         /* We do not set error in this case, because we still have enough
          * information about volume. */
-    } else {
-         disk->pci_controller = NULL;
     }
 
-    list = g_malloc0(sizeof(*list));
-    list->value = disk;
-    list->next = NULL;
-out_close:
-    CloseHandle(vol_h);
-out_free:
+err_close:
+    CloseHandle(disk_h);
+    return;
+}
+
+/* VSS provider works with volumes, thus there is no difference if
+ * the volume consist of spanned disks. Info about the first disk in the
+ * volume is returned for the spanned disk group (LVM) */
+static GuestDiskAddressList *build_guest_disk_info(char *guid, Error **errp)
+{
+    Error *local_err = NULL;
+    GuestDiskAddressList *list = NULL, *cur_item = NULL;
+    GuestDiskAddress *disk = NULL;
+    int i;
+    HANDLE vol_h;
+    DWORD size;
+    PVOLUME_DISK_EXTENTS extents = NULL;
+
+    /* strip final backslash */
+    char *name = g_strdup(guid);
+    if (g_str_has_suffix(name, "\\")) {
+        name[strlen(name) - 1] = 0;
+    }
+
+    g_debug("opening %s", name);
+    vol_h = CreateFile(name, 0, FILE_SHARE_READ, NULL, OPEN_EXISTING,
+                       0, NULL);
+    if (vol_h == INVALID_HANDLE_VALUE) {
+        error_setg_win32(errp, GetLastError(), "failed to open volume");
+        goto out;
+    }
+
+    /* Get list of extents */
+    g_debug("getting disk extents");
+    size = sizeof(VOLUME_DISK_EXTENTS);
+    extents = g_malloc0(size);
+    if (!DeviceIoControl(vol_h, IOCTL_VOLUME_GET_VOLUME_DISK_EXTENTS, NULL,
+                         0, extents, size, NULL, NULL)) {
+        DWORD last_err = GetLastError();
+        if (last_err == ERROR_MORE_DATA) {
+            /* Try once more with big enough buffer */
+            size = sizeof(VOLUME_DISK_EXTENTS)
+                + extents->NumberOfDiskExtents*sizeof(DISK_EXTENT);
+            g_free(extents);
+            extents = g_malloc0(size);
+            if (!DeviceIoControl(
+                    vol_h, IOCTL_VOLUME_GET_VOLUME_DISK_EXTENTS, NULL,
+                    0, extents, size, NULL, NULL)) {
+                error_setg_win32(errp, GetLastError(),
+                    "failed to get disk extents");
+                return NULL;
+            }
+        } else if (last_err == ERROR_INVALID_FUNCTION) {
+            /* Possibly CD-ROM or a shared drive. Try to pass the volume */
+            g_debug("volume not on disk");
+            disk = g_malloc0(sizeof(GuestDiskAddress));
+            disk->has_dev = true;
+            disk->dev = g_strdup(name);
+            get_single_disk_info(disk, &local_err);
+            if (local_err) {
+                g_debug("failed to get disk info, ignoring error: %s",
+                    error_get_pretty(local_err));
+                error_free(local_err);
+                goto out;
+            }
+            list = g_malloc0(sizeof(*list));
+            list->value = disk;
+            disk = NULL;
+            list->next = NULL;
+            goto out;
+        } else {
+            error_setg_win32(errp, GetLastError(),
+                "failed to get disk extents");
+            goto out;
+        }
+    }
+    g_debug("Number of extents: %lu", extents->NumberOfDiskExtents);
+
+    /* Go through each extent */
+    for (i = 0; i < extents->NumberOfDiskExtents; i++) {
+        disk = g_malloc0(sizeof(GuestDiskAddress));
+
+        /* Disk numbers directly correspond to numbers used in UNCs
+         *
+         * See documentation for DISK_EXTENT:
+         * https://docs.microsoft.com/en-us/windows/desktop/api/winioctl/ns-winioctl-_disk_extent
+         *
+         * See also Naming Files, Paths and Namespaces:
+         * https://docs.microsoft.com/en-us/windows/desktop/FileIO/naming-a-file#win32-device-namespaces
+         */
+        disk->has_dev = true;
+        disk->dev = g_strdup_printf("\\\\.\\PhysicalDrive%lu",
+            extents->Extents[i].DiskNumber);
+
+        get_single_disk_info(disk, &local_err);
+        if (local_err) {
+            error_propagate(errp, local_err);
+            goto out;
+        }
+        cur_item = g_malloc0(sizeof(*list));
+        cur_item->value = disk;
+        disk = NULL;
+        cur_item->next = list;
+        list = cur_item;
+    }
+
+
+out:
+    qapi_free_GuestDiskAddress(disk);
+    g_free(extents);
     g_free(name);
+
     return list;
 }
 
@@ -777,6 +985,13 @@ GuestFsfreezeStatus qmp_guest_fsfreeze_status(Error **errp)
  */
 int64_t qmp_guest_fsfreeze_freeze(Error **errp)
 {
+    return qmp_guest_fsfreeze_freeze_list(false, NULL, errp);
+}
+
+int64_t qmp_guest_fsfreeze_freeze_list(bool has_mountpoints,
+                                       strList *mountpoints,
+                                       Error **errp)
+{
     int i;
     Error *local_err = NULL;
 
@@ -790,7 +1005,7 @@ int64_t qmp_guest_fsfreeze_freeze(Error **errp)
     /* cannot risk guest agent blocking itself on a write in this state */
     ga_set_frozen(ga_state);
 
-    qga_vss_fsfreeze(&i, true, &local_err);
+    qga_vss_fsfreeze(&i, true, mountpoints, &local_err);
     if (local_err) {
         error_propagate(errp, local_err);
         goto error;
@@ -808,15 +1023,6 @@ error:
     return 0;
 }
 
-int64_t qmp_guest_fsfreeze_freeze_list(bool has_mountpoints,
-                                       strList *mountpoints,
-                                       Error **errp)
-{
-    error_setg(errp, QERR_UNSUPPORTED);
-
-    return 0;
-}
-
 /*
  * Thaw local file systems using Volume Shadow-copy Service.
  */
@@ -829,7 +1035,7 @@ int64_t qmp_guest_fsfreeze_thaw(Error **errp)
         return 0;
     }
 
-    qga_vss_fsfreeze(&i, false, errp);
+    qga_vss_fsfreeze(&i, false, NULL, errp);
 
     ga_unset_frozen(ga_state);
     return i;
@@ -1646,7 +1852,6 @@ GList *ga_command_blacklist_init(GList *blacklist)
         "guest-set-vcpus",
         "guest-get-memory-blocks", "guest-set-memory-blocks",
         "guest-get-memory-block-size",
-        "guest-fsfreeze-freeze-list",
         NULL};
     char **p = (char **)list_unsupported;
 
diff --git a/qga/installer/qemu-ga.wxs b/qga/installer/qemu-ga.wxs
index f751a7e9f7..64bf90bd85 100644
--- a/qga/installer/qemu-ga.wxs
+++ b/qga/installer/qemu-ga.wxs
@@ -78,7 +78,7 @@
               Account="LocalSystem"
               ErrorControl="ignore"
               Interactive="no"
-              Arguments="-d"
+              Arguments="-d --retry-path"
               >
             </ServiceInstall>
             <ServiceControl Id="StartService" Start="install" Stop="both" Remove="uninstall" Name="QEMU-GA" Wait="no" />
diff --git a/qga/main.c b/qga/main.c
index c399320d3c..87a0711c14 100644
--- a/qga/main.c
+++ b/qga/main.c
@@ -34,6 +34,7 @@
 #include "qemu/systemd.h"
 #include "qemu-version.h"
 #ifdef _WIN32
+#include <dbt.h>
 #include "qga/service-win32.h"
 #include "qga/vss-win32.h"
 #endif
@@ -58,6 +59,7 @@
 #endif
 #define QGA_SENTINEL_BYTE 0xFF
 #define QGA_CONF_DEFAULT CONFIG_QEMU_CONFDIR G_DIR_SEPARATOR_S "qemu-ga.conf"
+#define QGA_RETRY_INTERVAL 5
 
 static struct {
     const char *state_dir;
@@ -69,6 +71,8 @@ typedef struct GAPersistentState {
     int64_t fd_counter;
 } GAPersistentState;
 
+typedef struct GAConfig GAConfig;
+
 struct GAState {
     JSONMessageParser parser;
     GMainLoop *main_loop;
@@ -80,6 +84,7 @@ struct GAState {
     bool logging_enabled;
 #ifdef _WIN32
     GAService service;
+    HANDLE wakeup_event;
 #endif
     bool delimit_response;
     bool frozen;
@@ -94,6 +99,9 @@ struct GAState {
 #endif
     gchar *pstate_filepath;
     GAPersistentState pstate;
+    GAConfig *config;
+    int socket_activation;
+    bool force_exit;
 };
 
 struct GAState *ga_state;
@@ -113,8 +121,11 @@ static const char *ga_freeze_whitelist[] = {
 #ifdef _WIN32
 DWORD WINAPI service_ctrl_handler(DWORD ctrl, DWORD type, LPVOID data,
                                   LPVOID ctx);
+DWORD WINAPI handle_serial_device_events(DWORD type, LPVOID data);
 VOID WINAPI service_main(DWORD argc, TCHAR *argv[]);
 #endif
+static int run_agent(GAState *s);
+static void stop_agent(GAState *s, bool requested);
 
 static void
 init_dfl_pathnames(void)
@@ -151,7 +162,7 @@ static void quit_handler(int sig)
             WaitForSingleObject(hEventTimeout, 0);
             CloseHandle(hEventTimeout);
         }
-        qga_vss_fsfreeze(&i, false, &err);
+        qga_vss_fsfreeze(&i, false, NULL, &err);
         if (err) {
             g_debug("Error unfreezing filesystems prior to exiting: %s",
                 error_get_pretty(err));
@@ -163,9 +174,7 @@ static void quit_handler(int sig)
     }
     g_debug("received signal num %d, quitting", sig);
 
-    if (g_main_loop_is_running(ga_state->main_loop)) {
-        g_main_loop_quit(ga_state->main_loop);
-    }
+    stop_agent(ga_state, true);
 }
 
 #ifndef _WIN32
@@ -250,6 +259,10 @@ QEMU_COPYRIGHT "\n"
 "                    to list available RPCs)\n"
 "  -D, --dump-conf   dump a qemu-ga config file based on current config\n"
 "                    options / command-line parameters to stdout\n"
+"  -r, --retry-path  attempt re-opening path if it's unavailable or closed\n"
+"                    due to an error which may be recoverable in the future\n"
+"                    (virtio-serial driver re-install, serial device hot\n"
+"                    plug/unplug, etc.)\n"
 "  -h, --help        display this help and exit\n"
 "\n"
 QEMU_HELP_BOTTOM "\n"
@@ -609,6 +622,7 @@ static gboolean channel_event_cb(GIOCondition condition, gpointer data)
     switch (status) {
     case G_IO_STATUS_ERROR:
         g_warning("error reading channel");
+        stop_agent(s, false);
         return false;
     case G_IO_STATUS_NORMAL:
         buf[count] = 0;
@@ -666,6 +680,36 @@ static gboolean channel_init(GAState *s, const gchar *method, const gchar *path,
 }
 
 #ifdef _WIN32
+DWORD WINAPI handle_serial_device_events(DWORD type, LPVOID data)
+{
+    DWORD ret = NO_ERROR;
+    PDEV_BROADCAST_HDR broadcast_header = (PDEV_BROADCAST_HDR)data;
+
+    if (broadcast_header->dbch_devicetype == DBT_DEVTYP_DEVICEINTERFACE) {
+        switch (type) {
+            /* Device inserted */
+        case DBT_DEVICEARRIVAL:
+            /* Start QEMU-ga's service */
+            if (!SetEvent(ga_state->wakeup_event)) {
+                ret = GetLastError();
+            }
+            break;
+            /* Device removed */
+        case DBT_DEVICEQUERYREMOVE:
+        case DBT_DEVICEREMOVEPENDING:
+        case DBT_DEVICEREMOVECOMPLETE:
+            /* Stop QEMU-ga's service */
+            if (!ResetEvent(ga_state->wakeup_event)) {
+                ret = GetLastError();
+            }
+            break;
+        default:
+            ret = ERROR_CALL_NOT_IMPLEMENTED;
+        }
+    }
+    return ret;
+}
+
 DWORD WINAPI service_ctrl_handler(DWORD ctrl, DWORD type, LPVOID data,
                                   LPVOID ctx)
 {
@@ -677,9 +721,13 @@ DWORD WINAPI service_ctrl_handler(DWORD ctrl, DWORD type, LPVOID data,
         case SERVICE_CONTROL_STOP:
         case SERVICE_CONTROL_SHUTDOWN:
             quit_handler(SIGTERM);
+            SetEvent(ga_state->wakeup_event);
             service->status.dwCurrentState = SERVICE_STOP_PENDING;
             SetServiceStatus(service->status_handle, &service->status);
             break;
+        case SERVICE_CONTROL_DEVICEEVENT:
+            handle_serial_device_events(type, data);
+            break;
 
         default:
             ret = ERROR_CALL_NOT_IMPLEMENTED;
@@ -706,10 +754,24 @@ VOID WINAPI service_main(DWORD argc, TCHAR *argv[])
     service->status.dwServiceSpecificExitCode = NO_ERROR;
     service->status.dwCheckPoint = 0;
     service->status.dwWaitHint = 0;
+    DEV_BROADCAST_DEVICEINTERFACE notification_filter;
+    ZeroMemory(&notification_filter, sizeof(notification_filter));
+    notification_filter.dbcc_devicetype = DBT_DEVTYP_DEVICEINTERFACE;
+    notification_filter.dbcc_size = sizeof(DEV_BROADCAST_DEVICEINTERFACE);
+    notification_filter.dbcc_classguid = GUID_VIOSERIAL_PORT;
+
+    service->device_notification_handle =
+        RegisterDeviceNotification(service->status_handle,
+            &notification_filter, DEVICE_NOTIFY_SERVICE_HANDLE);
+    if (!service->device_notification_handle) {
+        g_critical("Failed to register device notification handle!\n");
+        return;
+    }
     SetServiceStatus(service->status_handle, &service->status);
 
-    g_main_loop_run(ga_state->main_loop);
+    run_agent(ga_state);
 
+    UnregisterDeviceNotification(service->device_notification_handle);
     service->status.dwCurrentState = SERVICE_STOPPED;
     SetServiceStatus(service->status_handle, &service->status);
 }
@@ -905,7 +967,7 @@ static GList *split_list(const gchar *str, const gchar *delim)
     return list;
 }
 
-typedef struct GAConfig {
+struct GAConfig {
     char *channel_path;
     char *method;
     char *log_filepath;
@@ -922,7 +984,8 @@ typedef struct GAConfig {
     int daemonize;
     GLogLevelFlags log_level;
     int dumpconf;
-} GAConfig;
+    bool retry_path;
+};
 
 static void config_load(GAConfig *config)
 {
@@ -971,6 +1034,10 @@ static void config_load(GAConfig *config)
         /* enable all log levels */
         config->log_level = G_LOG_LEVEL_MASK;
     }
+    if (g_key_file_has_key(keyfile, "general", "retry-path", NULL)) {
+        config->retry_path =
+            g_key_file_get_boolean(keyfile, "general", "retry-path", &gerr);
+    }
     if (g_key_file_has_key(keyfile, "general", "blacklist", NULL)) {
         config->bliststr =
             g_key_file_get_string(keyfile, "general", "blacklist", &gerr);
@@ -1032,6 +1099,8 @@ static void config_dump(GAConfig *config)
     g_key_file_set_string(keyfile, "general", "statedir", config->state_dir);
     g_key_file_set_boolean(keyfile, "general", "verbose",
                            config->log_level == G_LOG_LEVEL_MASK);
+    g_key_file_set_boolean(keyfile, "general", "retry-path",
+                           config->retry_path);
     tmp = list_join(config->blacklist, ',');
     g_key_file_set_string(keyfile, "general", "blacklist", tmp);
     g_free(tmp);
@@ -1050,7 +1119,7 @@ static void config_dump(GAConfig *config)
 
 static void config_parse(GAConfig *config, int argc, char **argv)
 {
-    const char *sopt = "hVvdm:p:l:f:F::b:s:t:D";
+    const char *sopt = "hVvdm:p:l:f:F::b:s:t:Dr";
     int opt_ind = 0, ch;
     const struct option lopt[] = {
         { "help", 0, NULL, 'h' },
@@ -1070,6 +1139,7 @@ static void config_parse(GAConfig *config, int argc, char **argv)
         { "service", 1, NULL, 's' },
 #endif
         { "statedir", 1, NULL, 't' },
+        { "retry-path", 0, NULL, 'r' },
         { NULL, 0, NULL, 0 }
     };
 
@@ -1114,6 +1184,9 @@ static void config_parse(GAConfig *config, int argc, char **argv)
         case 'D':
             config->dumpconf = 1;
             break;
+        case 'r':
+            config->retry_path = true;
+            break;
         case 'b': {
             if (is_help_option(optarg)) {
                 qmp_for_each_command(&ga_commands, ga_print_cmd, NULL);
@@ -1211,9 +1284,21 @@ static bool check_is_frozen(GAState *s)
     return false;
 }
 
-static int run_agent(GAState *s, GAConfig *config, int socket_activation)
+static GAState *initialize_agent(GAConfig *config, int socket_activation)
 {
-    ga_state = s;
+    GAState *s = g_new0(GAState, 1);
+
+    g_assert(ga_state == NULL);
+
+    s->log_level = config->log_level;
+    s->log_file = stderr;
+#ifdef CONFIG_FSFREEZE
+    s->fsfreeze_hook = config->fsfreeze_hook;
+#endif
+    s->pstate_filepath = g_strdup_printf("%s/qga.state", config->state_dir);
+    s->state_filepath_isfrozen = g_strdup_printf("%s/qga.state.isfrozen",
+                                                 config->state_dir);
+    s->frozen = check_is_frozen(s);
 
     g_log_set_default_handler(ga_log, s);
     g_log_set_fatal_mask(NULL, G_LOG_LEVEL_ERROR);
@@ -1229,7 +1314,7 @@ static int run_agent(GAState *s, GAConfig *config, int socket_activation)
     if (g_mkdir_with_parents(config->state_dir, S_IRWXU) == -1) {
         g_critical("unable to create (an ancestor of) the state directory"
                    " '%s': %s", config->state_dir, strerror(errno));
-        return EXIT_FAILURE;
+        return NULL;
     }
 #endif
 
@@ -1254,7 +1339,7 @@ static int run_agent(GAState *s, GAConfig *config, int socket_activation)
             if (!log_file) {
                 g_critical("unable to open specified log file: %s",
                            strerror(errno));
-                return EXIT_FAILURE;
+                return NULL;
             }
             s->log_file = log_file;
         }
@@ -1265,7 +1350,7 @@ static int run_agent(GAState *s, GAConfig *config, int socket_activation)
                                s->pstate_filepath,
                                ga_is_frozen(s))) {
         g_critical("failed to load persistent state");
-        return EXIT_FAILURE;
+        return NULL;
     }
 
     config->blacklist = ga_command_blacklist_init(config->blacklist);
@@ -1286,36 +1371,116 @@ static int run_agent(GAState *s, GAConfig *config, int socket_activation)
 #ifndef _WIN32
     if (!register_signal_handlers()) {
         g_critical("failed to register signal handlers");
-        return EXIT_FAILURE;
+        return NULL;
     }
 #endif
 
     s->main_loop = g_main_loop_new(NULL, false);
 
-    if (!channel_init(ga_state, config->method, config->channel_path,
-                      socket_activation ? FIRST_SOCKET_ACTIVATION_FD : -1)) {
+    s->config = config;
+    s->socket_activation = socket_activation;
+
+#ifdef _WIN32
+    s->wakeup_event = CreateEvent(NULL, TRUE, FALSE, TEXT("WakeUp"));
+    if (s->wakeup_event == NULL) {
+        g_critical("CreateEvent failed");
+        return NULL;
+    }
+#endif
+
+    ga_state = s;
+    return s;
+}
+
+static void cleanup_agent(GAState *s)
+{
+#ifdef _WIN32
+    CloseHandle(s->wakeup_event);
+#endif
+    if (s->command_state) {
+        ga_command_state_cleanup_all(s->command_state);
+        ga_command_state_free(s->command_state);
+        json_message_parser_destroy(&s->parser);
+    }
+    g_free(s->pstate_filepath);
+    g_free(s->state_filepath_isfrozen);
+    if (s->main_loop) {
+        g_main_loop_unref(s->main_loop);
+    }
+    g_free(s);
+    ga_state = NULL;
+}
+
+static int run_agent_once(GAState *s)
+{
+    if (!channel_init(s, s->config->method, s->config->channel_path,
+                      s->socket_activation ? FIRST_SOCKET_ACTIVATION_FD : -1)) {
         g_critical("failed to initialize guest agent channel");
         return EXIT_FAILURE;
     }
-#ifndef _WIN32
+
     g_main_loop_run(ga_state->main_loop);
+
+    if (s->channel) {
+        ga_channel_free(s->channel);
+    }
+
+    return EXIT_SUCCESS;
+}
+
+static void wait_for_channel_availability(GAState *s)
+{
+    g_warning("waiting for channel path...");
+#ifndef _WIN32
+    sleep(QGA_RETRY_INTERVAL);
 #else
-    if (config->daemonize) {
-        SERVICE_TABLE_ENTRY service_table[] = {
-            { (char *)QGA_SERVICE_NAME, service_main }, { NULL, NULL } };
-        StartServiceCtrlDispatcher(service_table);
-    } else {
-        g_main_loop_run(ga_state->main_loop);
+    DWORD dwWaitResult;
+
+    dwWaitResult = WaitForSingleObject(s->wakeup_event, INFINITE);
+
+    switch (dwWaitResult) {
+    case WAIT_OBJECT_0:
+        break;
+    case WAIT_TIMEOUT:
+        break;
+    default:
+        g_critical("WaitForSingleObject failed");
     }
 #endif
+}
 
-    return EXIT_SUCCESS;
+static int run_agent(GAState *s)
+{
+    int ret = EXIT_SUCCESS;
+
+    s->force_exit = false;
+
+    do {
+        ret = run_agent_once(s);
+        if (s->config->retry_path && !s->force_exit) {
+            g_warning("agent stopped unexpectedly, restarting...");
+            wait_for_channel_availability(s);
+        }
+    } while (s->config->retry_path && !s->force_exit);
+
+    return ret;
+}
+
+static void stop_agent(GAState *s, bool requested)
+{
+    if (!s->force_exit) {
+        s->force_exit = requested;
+    }
+
+    if (g_main_loop_is_running(s->main_loop)) {
+        g_main_loop_quit(s->main_loop);
+    }
 }
 
 int main(int argc, char **argv)
 {
     int ret = EXIT_SUCCESS;
-    GAState *s = g_new0(GAState, 1);
+    GAState *s;
     GAConfig *config = g_new0(GAConfig, 1);
     int socket_activation;
 
@@ -1383,44 +1548,37 @@ int main(int argc, char **argv)
         }
     }
 
-    s->log_level = config->log_level;
-    s->log_file = stderr;
-#ifdef CONFIG_FSFREEZE
-    s->fsfreeze_hook = config->fsfreeze_hook;
-#endif
-    s->pstate_filepath = g_strdup_printf("%s/qga.state", config->state_dir);
-    s->state_filepath_isfrozen = g_strdup_printf("%s/qga.state.isfrozen",
-                                                 config->state_dir);
-    s->frozen = check_is_frozen(s);
-
     if (config->dumpconf) {
         config_dump(config);
         goto end;
     }
 
-    ret = run_agent(s, config, socket_activation);
-
-end:
-    if (s->command_state) {
-        ga_command_state_cleanup_all(s->command_state);
-        ga_command_state_free(s->command_state);
-        json_message_parser_destroy(&s->parser);
+    s = initialize_agent(config, socket_activation);
+    if (!s) {
+        g_critical("error initializing guest agent");
+        goto end;
     }
-    if (s->channel) {
-        ga_channel_free(s->channel);
+
+#ifdef _WIN32
+    if (config->daemonize) {
+        SERVICE_TABLE_ENTRY service_table[] = {
+            { (char *)QGA_SERVICE_NAME, service_main }, { NULL, NULL } };
+        StartServiceCtrlDispatcher(service_table);
+    } else {
+        ret = run_agent(s);
     }
-    g_free(s->pstate_filepath);
-    g_free(s->state_filepath_isfrozen);
+#else
+    ret = run_agent(s);
+#endif
 
+    cleanup_agent(s);
+
+end:
     if (config->daemonize) {
         unlink(config->pid_filepath);
     }
 
     config_free(config);
-    if (s->main_loop) {
-        g_main_loop_unref(s->main_loop);
-    }
-    g_free(s);
 
     return ret;
 }
diff --git a/qga/qapi-schema.json b/qga/qapi-schema.json
index dfbc4a5e32..c6725b3ec8 100644
--- a/qga/qapi-schema.json
+++ b/qga/qapi-schema.json
@@ -834,13 +834,16 @@
 # @bus: bus id
 # @target: target id
 # @unit: unit id
+# @serial: serial number (since: 3.1)
+# @dev: device node (POSIX) or device UNC (Windows) (since: 3.1)
 #
 # Since: 2.2
 ##
 { 'struct': 'GuestDiskAddress',
   'data': {'pci-controller': 'GuestPCIAddress',
            'bus-type': 'GuestDiskBusType',
-           'bus': 'int', 'target': 'int', 'unit': 'int'} }
+           'bus': 'int', 'target': 'int', 'unit': 'int',
+           '*serial': 'str', '*dev': 'str'} }
 
 ##
 # @GuestFilesystemInfo:
diff --git a/qga/service-win32.h b/qga/service-win32.h
index 89e99dfede..7b16d69b57 100644
--- a/qga/service-win32.h
+++ b/qga/service-win32.h
@@ -20,9 +20,13 @@
 #define QGA_SERVICE_NAME         "qemu-ga"
 #define QGA_SERVICE_DESCRIPTION  "Enables integration with QEMU machine emulator and virtualizer."
 
+static const GUID GUID_VIOSERIAL_PORT = { 0x6fde7521, 0x1b65, 0x48ae,
+{ 0xb6, 0x28, 0x80, 0xbe, 0x62, 0x1, 0x60, 0x26 } };
+
 typedef struct GAService {
     SERVICE_STATUS status;
     SERVICE_STATUS_HANDLE status_handle;
+    HDEVNOTIFY device_notification_handle;
 } GAService;
 
 int ga_install_service(const char *path, const char *logfile,
diff --git a/qga/vss-win32.c b/qga/vss-win32.c
index a541f3ae01..f444a25a70 100644
--- a/qga/vss-win32.c
+++ b/qga/vss-win32.c
@@ -147,7 +147,8 @@ void ga_uninstall_vss_provider(void)
 }
 
 /* Call VSS requester and freeze/thaw filesystems and applications */
-void qga_vss_fsfreeze(int *nr_volume, bool freeze, Error **errp)
+void qga_vss_fsfreeze(int *nr_volume, bool freeze,
+                      strList *mountpoints, Error **errp)
 {
     const char *func_name = freeze ? "requester_freeze" : "requester_thaw";
     QGAVSSRequesterFunc func;
@@ -164,5 +165,5 @@ void qga_vss_fsfreeze(int *nr_volume, bool freeze, Error **errp)
         return;
     }
 
-    func(nr_volume, &errset);
+    func(nr_volume, mountpoints, &errset);
 }
diff --git a/qga/vss-win32.h b/qga/vss-win32.h
index 4f8e39aa5c..ce2abe5a72 100644
--- a/qga/vss-win32.h
+++ b/qga/vss-win32.h
@@ -22,6 +22,7 @@ bool vss_initialized(void);
 int ga_install_vss_provider(void);
 void ga_uninstall_vss_provider(void);
 
-void qga_vss_fsfreeze(int *nr_volume, bool freeze, Error **errp);
+void qga_vss_fsfreeze(int *nr_volume, bool freeze,
+                      strList *mountpints, Error **errp);
 
 #endif
diff --git a/qga/vss-win32/requester.cpp b/qga/vss-win32/requester.cpp
index 3d9c9716c0..5378c55d23 100644
--- a/qga/vss-win32/requester.cpp
+++ b/qga/vss-win32/requester.cpp
@@ -234,7 +234,7 @@ out:
     }
 }
 
-void requester_freeze(int *num_vols, ErrorSet *errset)
+void requester_freeze(int *num_vols, void *mountpoints, ErrorSet *errset)
 {
     COMPointer<IVssAsync> pAsync;
     HANDLE volume;
@@ -246,6 +246,7 @@ void requester_freeze(int *num_vols, ErrorSet *errset)
     WCHAR short_volume_name[64], *display_name = short_volume_name;
     DWORD wait_status;
     int num_fixed_drives = 0, i;
+    int num_mount_points = 0;
 
     if (vss_ctx.pVssbc) { /* already frozen */
         *num_vols = 0;
@@ -337,39 +338,73 @@ void requester_freeze(int *num_vols, ErrorSet *errset)
         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) {
+    if (mountpoints) {
+        PWCHAR volume_name_wchar;
+        for (volList *list = (volList *)mountpoints; list; list = list->next) {
+            size_t len = strlen(list->value) + 1;
+            size_t converted = 0;
             VSS_ID pid;
-            hr = vss_ctx.pVssbc->AddToSnapshotSet(short_volume_name,
+
+            volume_name_wchar = new wchar_t[len];
+            mbstowcs_s(&converted, volume_name_wchar, len,
+                       list->value, _TRUNCATE);
+
+            hr = vss_ctx.pVssbc->AddToSnapshotSet(volume_name_wchar,
                                                   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);
+                        volume_name_wchar);
+                delete volume_name_wchar;
                 goto out;
             }
-            num_fixed_drives++;
+            num_mount_points++;
+
+            delete volume_name_wchar;
         }
-        if (!FindNextVolumeW(volume, short_volume_name,
-                             sizeof(short_volume_name))) {
-            FindVolumeClose(volume);
-            break;
+
+        if (num_mount_points == 0) {
+            /* If there is no valid mount points, just exit. */
+            goto out;
         }
     }
 
-    if (num_fixed_drives == 0) {
-        goto out; /* If there is no fixed drive, just exit. */
+    if (!mountpoints) {
+        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());
@@ -435,7 +470,12 @@ void requester_freeze(int *num_vols, ErrorSet *errset)
         goto out;
     }
 
-    *num_vols = vss_ctx.cFrozenVols = num_fixed_drives;
+    if (mountpoints) {
+        *num_vols = vss_ctx.cFrozenVols = num_mount_points;
+    } else {
+        *num_vols = vss_ctx.cFrozenVols = num_fixed_drives;
+    }
+
     return;
 
 out:
@@ -449,7 +489,7 @@ out1:
 }
 
 
-void requester_thaw(int *num_vols, ErrorSet *errset)
+void requester_thaw(int *num_vols, void *mountpints, ErrorSet *errset)
 {
     COMPointer<IVssAsync> pAsync;
 
diff --git a/qga/vss-win32/requester.h b/qga/vss-win32/requester.h
index 2a39d734a2..5a8e8faf0c 100644
--- a/qga/vss-win32/requester.h
+++ b/qga/vss-win32/requester.h
@@ -34,9 +34,16 @@ typedef struct 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);
+typedef struct volList volList;
+
+struct volList {
+    volList *next;
+    char *value;
+};
+
+typedef void (*QGAVSSRequesterFunc)(int *, void *, ErrorSet *);
+void requester_freeze(int *num_vols, void *volList, ErrorSet *errset);
+void requester_thaw(int *num_vols, void *volList, ErrorSet *errset);
 
 #ifdef __cplusplus
 }