[Qemu-devel] [PATCH v7 16/18] xen: automatically create XenBlockDevice-s

[Paul Durrant]

This patch adds create and destroy function for XenBlockDevice-s so that
they can be created automatically when the Xen toolstack instantiates a new
PV backend via xenstore. When the XenBlockDevice is created this way it is
also necessary to create a 'drive' which matches the configuration that the
Xen toolstack has written into xenstore. This is done by formulating the
parameters necessary for each 'blockdev' layer of the drive and then using
qmp_blockdev_add() to create the layers. Also, for compatibility with the
legacy 'xen_disk' implementation, an iothread is automatically created for
the new XenBlockDevice. This, like the driver layers, will be destroyed
after the XenBlockDevice is unrealized.

The legacy backend scan for 'qdisk' is removed by this patch, which makes
the 'xen_disk' code is redundant. The code will be removed by a subsequent
patch.

Signed-off-by: Paul Durrant <address@hidden>
---
Cc: Anthony Perard <address@hidden>
Cc: Kevin Wolf <address@hidden>
Cc: Max Reitz <address@hidden>
Cc: Stefano Stabellini <address@hidden>

v7:
 - Don't use qobject_input_visitor_new_flat_confused()

v5:
 - Extensively re-worked to avoid using drive_new() and use
   qmp_blockdev_add() instead
 - Also use qmp_object_add() for IOThread
 - Dropped Anthony's R-b because of the code changes

v2:
 - Get rid of error_abort
 - Don't use qdev_init_nofail()
 - Explain why file locking needs to be off
---
 hw/block/trace-events       |   4 +
 hw/block/xen-block.c        | 404 ++++++++++++++++++++++++++++++++++++
 hw/xen/xen-legacy-backend.c |   1 -
 include/hw/xen/xen-block.h  |  13 ++
 4 files changed, 421 insertions(+), 1 deletion(-)

diff --git a/hw/block/trace-events b/hw/block/trace-events
index 89e258319c..55e5a5500c 100644
--- a/hw/block/trace-events
+++ b/hw/block/trace-events
@@ -137,3 +137,7 @@ xen_disk_realize(void) ""
 xen_disk_unrealize(void) ""
 xen_cdrom_realize(void) ""
 xen_cdrom_unrealize(void) ""
+xen_block_blockdev_add(char *str) "%s"
+xen_block_blockdev_del(const char *node_name) "%s"
+xen_block_device_create(unsigned int number) "%u"
+xen_block_device_destroy(unsigned int number) "%u"
diff --git a/hw/block/xen-block.c b/hw/block/xen-block.c
index a7c37c185a..1e34fe1527 100644
--- a/hw/block/xen-block.c
+++ b/hw/block/xen-block.c
@@ -7,12 +7,20 @@
 
 #include "qemu/osdep.h"
 #include "qemu/cutils.h"
+#include "qemu/option.h"
 #include "qapi/error.h"
+#include "qapi/qapi-commands-block-core.h"
+#include "qapi/qapi-commands-misc.h"
+#include "qapi/qapi-visit-block-core.h"
+#include "qapi/qobject-input-visitor.h"
 #include "qapi/visitor.h"
+#include "qapi/qmp/qdict.h"
+#include "qapi/qmp/qstring.h"
 #include "hw/hw.h"
 #include "hw/xen/xen_common.h"
 #include "hw/block/xen_blkif.h"
 #include "hw/xen/xen-block.h"
+#include "hw/xen/xen-backend.h"
 #include "sysemu/blockdev.h"
 #include "sysemu/block-backend.h"
 #include "sysemu/iothread.h"
@@ -474,6 +482,7 @@ static void xen_block_class_init(ObjectClass *class, void 
*data)
     DeviceClass *dev_class = DEVICE_CLASS(class);
     XenDeviceClass *xendev_class = XEN_DEVICE_CLASS(class);
 
+    xendev_class->backend = "qdisk";
     xendev_class->device = "vbd";
     xendev_class->get_name = xen_block_get_name;
     xendev_class->realize = xen_block_realize;
@@ -586,3 +595,398 @@ static void xen_block_register_types(void)
 }
 
 type_init(xen_block_register_types)
+
+static void xen_block_blockdev_del(const char *node_name, Error **errp)
+{
+    trace_xen_block_blockdev_del(node_name);
+
+    qmp_blockdev_del(node_name, errp);
+}
+
+static char *xen_block_blockdev_add(const char *id, QDict *qdict,
+                                    Error **errp)
+{
+    const char *driver = qdict_get_try_str(qdict, "driver");
+    BlockdevOptions *options = NULL;
+    Error *local_err = NULL;
+    char *node_name;
+    Visitor *v;
+
+    if (!driver) {
+        error_setg(errp, "no 'driver' parameter");
+        return NULL;
+    }
+
+    node_name = g_strdup_printf("%s-%s", id, driver);
+    qdict_put_str(qdict, "node-name", node_name);
+
+    trace_xen_block_blockdev_add(node_name);
+
+    v = qobject_input_visitor_new(QOBJECT(qdict));
+    visit_type_BlockdevOptions(v, NULL, &options, &local_err);
+    visit_free(v);
+
+    if (local_err) {
+        error_propagate(errp, local_err);
+        goto fail;
+    }
+
+    qmp_blockdev_add(options, &local_err);
+
+    if (local_err) {
+        error_propagate(errp, local_err);
+        goto fail;
+    }
+
+    qapi_free_BlockdevOptions(options);
+
+    return node_name;
+
+fail:
+    if (options) {
+        qapi_free_BlockdevOptions(options);
+    }
+    g_free(node_name);
+
+    return NULL;
+}
+
+static void xen_block_drive_destroy(XenBlockDrive *drive, Error **errp)
+{
+    while (drive->layers-- != 0) {
+        char *node_name = drive->node_name[drive->layers];
+        Error *local_err = NULL;
+
+        xen_block_blockdev_del(node_name, &local_err);
+        if (local_err) {
+            error_propagate(errp, local_err);
+            drive->layers++;
+            return;
+        }
+    }
+    g_free(drive->id);
+    g_free(drive);
+}
+
+static void xen_block_drive_layer_add(XenBlockDrive *drive, QDict *qdict,
+                                      Error **errp)
+{
+    unsigned int i = drive->layers;
+    char *node_name;
+
+    g_assert(drive->layers < ARRAY_SIZE(drive->node_name));
+
+    if (i != 0) {
+        /* Link to the lower layer */
+        qdict_put_str(qdict, "file", drive->node_name[i - 1]);
+    }
+
+    node_name = xen_block_blockdev_add(drive->id, qdict, errp);
+    if (!node_name) {
+        return;
+    }
+
+    drive->node_name[i] = node_name;
+    drive->layers++;
+}
+
+static XenBlockDrive *xen_block_drive_create(const char *id,
+                                             const char *device_type,
+                                             QDict *opts, Error **errp)
+{
+    const char *params = qdict_get_try_str(opts, "params");
+    const char *mode = qdict_get_try_str(opts, "mode");
+    const char *direct_io_safe = qdict_get_try_str(opts, "direct-io-safe");
+    const char *discard_enable = qdict_get_try_str(opts, "discard-enable");
+    char *driver = NULL;
+    char *filename = NULL;
+    XenBlockDrive *drive = NULL;
+    Error *local_err = NULL;
+    QDict *qdict;
+
+    if (params) {
+        char **v = g_strsplit(params, ":", 2);
+
+        if (v[1] == NULL) {
+            filename = g_strdup(v[0]);
+            driver = g_strdup("file");
+        } else {
+            if (strcmp(v[0], "aio") == 0) {
+                driver = g_strdup("file");
+            } else if (strcmp(v[0], "vhd") == 0) {
+                driver = g_strdup("vpc");
+            } else {
+                driver = g_strdup(v[0]);
+            }
+            filename = g_strdup(v[1]);
+        }
+
+        g_strfreev(v);
+    }
+
+    if (!filename) {
+        error_setg(errp, "no filename");
+        goto done;
+    }
+    assert(driver);
+
+    drive = g_new0(XenBlockDrive, 1);
+    drive->id = g_strdup(id);
+
+    qdict = qdict_new();
+
+    qdict_put_str(qdict, "driver", "file");
+    qdict_put_str(qdict, "filename", filename);
+
+    if (mode && *mode != 'w') {
+        qdict_put_bool(qdict, "read-only", true);
+    }
+
+    if (direct_io_safe) {
+        unsigned long value;
+
+        if (!qemu_strtoul(direct_io_safe, NULL, 2, &value) && !!value) {
+            QDict *cache_qdict = qdict_new();
+
+            qdict_put_bool(cache_qdict, "direct", true);
+            qdict_put_obj(qdict, "cache", QOBJECT(cache_qdict));
+
+            qdict_put_str(qdict, "aio", "native");
+        }
+    }
+
+    if (discard_enable) {
+        unsigned long value;
+
+        if (!qemu_strtoul(discard_enable, NULL, 2, &value) && !!value) {
+            qdict_put_str(qdict, "discard", "unmap");
+        }
+    }
+
+    /*
+     * It is necessary to turn file locking off as an emulated device
+     * may have already opened the same image file.
+     */
+    qdict_put_str(qdict, "locking", "off");
+
+    xen_block_drive_layer_add(drive, qdict, &local_err);
+    qobject_unref(qdict);
+
+    if (local_err) {
+        error_propagate(errp, local_err);
+        goto done;
+    }
+
+    /* If the image is a raw file then we are done */
+    if (!strcmp(driver, "file")) {
+        goto done;
+    }
+
+    qdict = qdict_new();
+
+    qdict_put_str(qdict, "driver", driver);
+
+    xen_block_drive_layer_add(drive, qdict, &local_err);
+    qobject_unref(qdict);
+
+done:
+    g_free(driver);
+    g_free(filename);
+
+    if (local_err) {
+        xen_block_drive_destroy(drive, NULL);
+        return NULL;
+    }
+
+    return drive;
+}
+
+static const char *xen_block_drive_get_node_name(XenBlockDrive *drive)
+{
+    return drive->layers ? drive->node_name[drive->layers - 1] : "";
+}
+
+static void xen_block_iothread_destroy(XenBlockIOThread *iothread,
+                                       Error **errp)
+{
+    qmp_object_del(iothread->id, errp);
+
+    g_free(iothread->id);
+    g_free(iothread);
+}
+
+static XenBlockIOThread *xen_block_iothread_create(const char *id,
+                                                   Error **errp)
+{
+    XenBlockIOThread *iothread = g_new(XenBlockIOThread, 1);
+    Error *local_err = NULL;
+
+    iothread->id = g_strdup(id);
+
+    qmp_object_add(TYPE_IOTHREAD, id, false, NULL, &local_err);
+    if (local_err) {
+        error_propagate(errp, local_err);
+
+        g_free(iothread->id);
+        g_free(iothread);
+        return NULL;
+    }
+
+    return iothread;
+}
+
+static void xen_block_device_create(XenBackendInstance *backend,
+                                    QDict *opts, Error **errp)
+{
+    XenBus *xenbus = xen_backend_get_bus(backend);
+    const char *name = xen_backend_get_name(backend);
+    unsigned long number;
+    const char *vdev, *device_type;
+    XenBlockDrive *drive = NULL;
+    XenBlockIOThread *iothread = NULL;
+    XenDevice *xendev = NULL;
+    Error *local_err = NULL;
+    const char *type;
+    XenBlockDevice *blockdev;
+
+    if (qemu_strtoul(name, NULL, 10, &number)) {
+        error_setg(errp, "failed to parse name '%s'", name);
+        goto fail;
+    }
+
+    trace_xen_block_device_create(number);
+
+    vdev = qdict_get_try_str(opts, "dev");
+    if (!vdev) {
+        error_setg(errp, "no dev parameter");
+        goto fail;
+    }
+
+    device_type = qdict_get_try_str(opts, "device-type");
+    if (!device_type) {
+        error_setg(errp, "no device-type parameter");
+        goto fail;
+    }
+
+    if (!strcmp(device_type, "disk")) {
+        type = TYPE_XEN_DISK_DEVICE;
+    } else if (!strcmp(device_type, "cdrom")) {
+        type = TYPE_XEN_CDROM_DEVICE;
+    } else {
+        error_setg(errp, "invalid device-type parameter '%s'", device_type);
+        goto fail;
+    }
+
+    drive = xen_block_drive_create(vdev, device_type, opts, &local_err);
+    if (!drive) {
+        error_propagate_prepend(errp, local_err, "failed to create drive: ");
+        goto fail;
+    }
+
+    iothread = xen_block_iothread_create(vdev, &local_err);
+    if (local_err) {
+        error_propagate_prepend(errp, local_err,
+                                "failed to create iothread: ");
+        goto fail;
+    }
+
+    xendev = XEN_DEVICE(qdev_create(BUS(xenbus), type));
+    blockdev = XEN_BLOCK_DEVICE(xendev);
+
+    object_property_set_str(OBJECT(xendev), vdev, "vdev", &local_err);
+    if (local_err) {
+        error_propagate_prepend(errp, local_err, "failed to set 'vdev': ");
+        goto fail;
+    }
+
+    object_property_set_str(OBJECT(xendev),
+                            xen_block_drive_get_node_name(drive), "drive",
+                            &local_err);
+    if (local_err) {
+        error_propagate_prepend(errp, local_err, "failed to set 'drive': ");
+        goto fail;
+    }
+
+    object_property_set_str(OBJECT(xendev), iothread->id, "iothread",
+                            &local_err);
+    if (local_err) {
+        error_propagate_prepend(errp, local_err,
+                                "failed to set 'iothread': ");
+        goto fail;
+    }
+
+    blockdev->iothread = iothread;
+    blockdev->drive = drive;
+
+    object_property_set_bool(OBJECT(xendev), true, "realized", &local_err);
+    if (local_err) {
+        error_propagate_prepend(errp, local_err,
+                                "realization of device %s failed: ",
+                                type);
+        goto fail;
+    }
+
+    xen_backend_set_device(backend, xendev);
+    return;
+
+fail:
+    if (xendev) {
+        object_unparent(OBJECT(xendev));
+    }
+
+    if (iothread) {
+        xen_block_iothread_destroy(iothread, NULL);
+    }
+
+    if (drive) {
+        xen_block_drive_destroy(drive, NULL);
+    }
+}
+
+static void xen_block_device_destroy(XenBackendInstance *backend,
+                                     Error **errp)
+{
+    XenDevice *xendev = xen_backend_get_device(backend);
+    XenBlockDevice *blockdev = XEN_BLOCK_DEVICE(xendev);
+    XenBlockVdev *vdev = &blockdev->props.vdev;
+    XenBlockDrive *drive = blockdev->drive;
+    XenBlockIOThread *iothread = blockdev->iothread;
+
+    trace_xen_block_device_destroy(vdev->number);
+
+    object_unparent(OBJECT(xendev));
+
+    if (iothread) {
+        Error *local_err = NULL;
+
+        xen_block_iothread_destroy(iothread, &local_err);
+        if (local_err) {
+            error_propagate_prepend(errp, local_err,
+                                "failed to destroy iothread: ");
+            return;
+        }
+    }
+
+    if (drive) {
+        Error *local_err = NULL;
+
+        xen_block_drive_destroy(drive, &local_err);
+        if (local_err) {
+            error_propagate_prepend(errp, local_err,
+                                "failed to destroy drive: ");
+        }
+    }
+}
+
+static const XenBackendInfo xen_block_backend_info = {
+    .type = "qdisk",
+    .create = xen_block_device_create,
+    .destroy = xen_block_device_destroy,
+};
+
+static void xen_block_register_backend(void)
+{
+    xen_backend_register(&xen_block_backend_info);
+}
+
+xen_backend_init(xen_block_register_backend);
diff --git a/hw/xen/xen-legacy-backend.c b/hw/xen/xen-legacy-backend.c
index 0c26023799..fb227de35d 100644
--- a/hw/xen/xen-legacy-backend.c
+++ b/hw/xen/xen-legacy-backend.c
@@ -753,7 +753,6 @@ void xen_be_register_common(void)
 
     xen_be_register("console", &xen_console_ops);
     xen_be_register("vkbd", &xen_kbdmouse_ops);
-    xen_be_register("qdisk", &xen_blkdev_ops);
 #ifdef CONFIG_VIRTFS
     xen_be_register("9pfs", &xen_9pfs_ops);
 #endif
diff --git a/include/hw/xen/xen-block.h b/include/hw/xen/xen-block.h
index c4223f9be1..6f5d675edb 100644
--- a/include/hw/xen/xen-block.h
+++ b/include/hw/xen/xen-block.h
@@ -29,6 +29,7 @@ typedef struct XenBlockVdev {
     unsigned long number;
 } XenBlockVdev;
 
+
 typedef struct XenBlockProperties {
     XenBlockVdev vdev;
     BlockConf conf;
@@ -36,12 +37,24 @@ typedef struct XenBlockProperties {
     IOThread *iothread;
 } XenBlockProperties;
 
+typedef struct XenBlockDrive {
+    char *id;
+    char *node_name[2];
+    unsigned int layers;
+} XenBlockDrive;
+
+typedef struct XenBlockIOThread {
+    char *id;
+} XenBlockIOThread;
+
 typedef struct XenBlockDevice {
     XenDevice xendev;
     XenBlockProperties props;
     const char *device_type;
     unsigned int info;
     XenBlockDataPlane *dataplane;
+    XenBlockDrive *drive;
+    XenBlockIOThread *iothread;
 } XenBlockDevice;
 
 typedef void (*XenBlockDeviceRealize)(XenBlockDevice *blockdev, Error **errp);
-- 
2.20.1.2.gb21ebb6