[v9,16/18] xen: automatically create XenBlockDevice-s
diff mbox series

Message ID 20190108144903.8249-17-paul.durrant@citrix.com
State New
Headers show
Series
  • Xen PV backend 'qdevification'
Related show

Commit Message

Paul Durrant Jan. 8, 2019, 2:49 p.m. UTC
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 <paul.durrant@citrix.com>
Signed-off-by: Anthony Perard <anthony.perard@citrix.com>
---
Cc: Kevin Wolf <kwolf@redhat.com>
Cc: Max Reitz <mreitz@redhat.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>

v9:
 - Squash the layers with patch from Anthony

v8:
 - Add 'raw' image layer for raw images

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        | 374 ++++++++++++++++++++++++++++++++++++
 hw/xen/xen-legacy-backend.c |   1 -
 include/hw/xen/xen-block.h  |  12 ++
 4 files changed, 390 insertions(+), 1 deletion(-)

Comments

Anthony PERARD Jan. 9, 2019, 12:09 p.m. UTC | #1
On Tue, Jan 08, 2019 at 02:49:01PM +0000, Paul Durrant wrote:
> 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 <paul.durrant@citrix.com>
> Signed-off-by: Anthony Perard <anthony.perard@citrix.com>
> ---

> diff --git a/hw/block/xen-block.c b/hw/block/xen-block.c
> index a7c37c185a..c6ec1d9543 100644
> --- a/hw/block/xen-block.c
> +++ b/hw/block/xen-block.c
> @@ -7,12 +7,20 @@
...

> +static XenBlockDrive *xen_block_drive_create(const char *id,
> +                                             const char *device_type,
> +                                             QDict *opts, Error **errp)
> +{
...
> +    Error *local_err = NULL;
...
> +    if (!filename) {
> +        error_setg(errp, "no filename");
> +        goto done;
> +    }
...
> +    drive->node_name = xen_block_blockdev_add(drive->id, driver_layer,
> +                                              &local_err);
> +
> +done:
> +    g_free(driver);
> +    g_free(filename);
> +
> +    if (local_err) {

When xen_block_blockdev_add failed, it sets local_err, but nothing after
sets errp. I'm going to add this while preparing the pull request:

    error_propagate(errp, local_err);

Is this fine with you?

With that fix, I think the series is ready, so:
Reviewed-by: Anthony PERARD <anthony.perard@citrix.com>

> +        xen_block_drive_destroy(drive, NULL);
> +        return NULL;
> +    }
> +
> +    return drive;
> +}

There is still the warning about using the 'file' driver when
'host_device' should be use, but I think we can try to fix that later.

Thanks,
Paul Durrant Jan. 9, 2019, 12:30 p.m. UTC | #2
> -----Original Message-----
> From: Anthony PERARD [mailto:anthony.perard@citrix.com]
> Sent: 09 January 2019 12:09
> To: Paul Durrant <Paul.Durrant@citrix.com>
> Cc: qemu-devel@nongnu.org; qemu-block@nongnu.org; xen-
> devel@lists.xenproject.org; Kevin Wolf <kwolf@redhat.com>; Max Reitz
> <mreitz@redhat.com>; Stefano Stabellini <sstabellini@kernel.org>
> Subject: Re: [PATCH v9 16/18] xen: automatically create XenBlockDevice-s
> 
> On Tue, Jan 08, 2019 at 02:49:01PM +0000, Paul Durrant wrote:
> > 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 <paul.durrant@citrix.com>
> > Signed-off-by: Anthony Perard <anthony.perard@citrix.com>
> > ---
> 
> > diff --git a/hw/block/xen-block.c b/hw/block/xen-block.c
> > index a7c37c185a..c6ec1d9543 100644
> > --- a/hw/block/xen-block.c
> > +++ b/hw/block/xen-block.c
> > @@ -7,12 +7,20 @@
> ...
> 
> > +static XenBlockDrive *xen_block_drive_create(const char *id,
> > +                                             const char *device_type,
> > +                                             QDict *opts, Error **errp)
> > +{
> ...
> > +    Error *local_err = NULL;
> ...
> > +    if (!filename) {
> > +        error_setg(errp, "no filename");
> > +        goto done;
> > +    }
> ...
> > +    drive->node_name = xen_block_blockdev_add(drive->id, driver_layer,
> > +                                              &local_err);
> > +
> > +done:
> > +    g_free(driver);
> > +    g_free(filename);
> > +
> > +    if (local_err) {
> 
> When xen_block_blockdev_add failed, it sets local_err, but nothing after
> sets errp. I'm going to add this while preparing the pull request:
> 
>     error_propagate(errp, local_err);
> 
> Is this fine with you?

Yes, that's fine... the error should have indeed been propagated.

> 
> With that fix, I think the series is ready, so:
> Reviewed-by: Anthony PERARD <anthony.perard@citrix.com>
> 

Thanks.

> > +        xen_block_drive_destroy(drive, NULL);
> > +        return NULL;
> > +    }
> > +
> > +    return drive;
> > +}
> 
> There is still the warning about using the 'file' driver when
> 'host_device' should be use, but I think we can try to fix that later.

TBH I'm hoping this code can go away before we have to worry about it. We need to teach libxl how to issue the necessary QMP commands directly; it should know the difference between a file and a device.

  Paul

> 
> Thanks,
> 
> --
> Anthony PERARD

Patch
diff mbox series

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..c6ec1d9543 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 +595,368 @@  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)
+{
+    char *node_name = drive->node_name;
+
+    if (node_name) {
+        Error *local_err = NULL;
+
+        xen_block_blockdev_del(node_name, &local_err);
+        if (local_err) {
+            error_propagate(errp, local_err);
+            return;
+        }
+        g_free(node_name);
+        drive->node_name = NULL;
+    }
+    g_free(drive->id);
+    g_free(drive);
+}
+
+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 *file_layer;
+    QDict *driver_layer;
+
+    if (params) {
+        char **v = g_strsplit(params, ":", 2);
+
+        if (v[1] == NULL) {
+            filename = g_strdup(v[0]);
+            driver = g_strdup("raw");
+        } else {
+            if (strcmp(v[0], "aio") == 0) {
+                driver = g_strdup("raw");
+            } 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);
+
+    file_layer = qdict_new();
+
+    qdict_put_str(file_layer, "driver", "file");
+    qdict_put_str(file_layer, "filename", filename);
+
+    if (mode && *mode != 'w') {
+        qdict_put_bool(file_layer, "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(file_layer, "cache", QOBJECT(cache_qdict));
+
+            qdict_put_str(file_layer, "aio", "native");
+        }
+    }
+
+    if (discard_enable) {
+        unsigned long value;
+
+        if (!qemu_strtoul(discard_enable, NULL, 2, &value) && !!value) {
+            qdict_put_str(file_layer, "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(file_layer, "locking", "off");
+
+    driver_layer = qdict_new();
+
+    qdict_put_str(driver_layer, "driver", driver);
+    qdict_put_obj(driver_layer, "file", QOBJECT(file_layer));
+
+    g_assert(!drive->node_name);
+    drive->node_name = xen_block_blockdev_add(drive->id, driver_layer,
+                                              &local_err);
+
+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->node_name ? drive->node_name : "";
+}
+
+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 41419763c8..36fd1e9b09 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..11d351b4b3 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 +37,23 @@  typedef struct XenBlockProperties {
     IOThread *iothread;
 } XenBlockProperties;
 
+typedef struct XenBlockDrive {
+    char *id;
+    char *node_name;
+} 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);