[v2,11/24] hw/xen: automatically assign device index to block devices

Commit Message

David Woodhouse Oct. 19, 2023, 3:40 p.m. UTC

From: David Woodhouse <[e-mail]>

There's no need to force the user to assign a vdev. We can automatically
assign one, starting at xvda and searching until we find the first disk
name that's unused.

This means we can now allow '-drive if=xen,file=xxx' to work without an
explicit separate -driver argument, just like if=virtio.

Rip out the legacy handling from the xenpv machine, which was scribbling
over any disks configured by the toolstack, and didn't work with anything
but raw images.

Signed-off-by: David Woodhouse <[e-mail]>
Acked-by: Kevin Wolf <[e-mail]>
---
 blockdev.c                          | 15 +++++++++---
 hw/block/xen-block.c                | 38 +++++++++++++++++++++++++++++
 hw/xen/xen_devconfig.c              | 28 ---------------------
 hw/xenpv/xen_machine_pv.c           |  9 -------
 include/hw/xen/xen-legacy-backend.h |  1 -
 5 files changed, 50 insertions(+), 41 deletions(-)

Patch

diff --git a/blockdev.c b/blockdev.c
index a01c62596b..5d9f2e5395 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -255,13 +255,13 @@  void drive_check_orphaned(void)
          * Ignore default drives, because we create certain default
          * drives unconditionally, then leave them unclaimed.  Not the
          * users fault.
-         * Ignore IF_VIRTIO, because it gets desugared into -device,
-         * so we can leave failing to -device.
+         * Ignore IF_VIRTIO or IF_XEN, because it gets desugared into
+         * -device, so we can leave failing to -device.
          * Ignore IF_NONE, because leaving unclaimed IF_NONE remains
          * available for device_add is a feature.
          */
         if (dinfo->is_default || dinfo->type == IF_VIRTIO
-            || dinfo->type == IF_NONE) {
+            || dinfo->type == IF_XEN || dinfo->type == IF_NONE) {
             continue;
         }
         if (!blk_get_attached_dev(blk)) {
@@ -977,6 +977,15 @@  DriveInfo *drive_new(QemuOpts *all_opts, BlockInterfaceType block_default_type,
         qemu_opt_set(devopts, "driver", "virtio-blk", &error_abort);
         qemu_opt_set(devopts, "drive", qdict_get_str(bs_opts, "id"),
                      &error_abort);
+    } else if (type == IF_XEN) {
+        QemuOpts *devopts;
+        devopts = qemu_opts_create(qemu_find_opts("device"), NULL, 0,
+                                   &error_abort);
+        qemu_opt_set(devopts, "driver",
+                     (media == MEDIA_CDROM) ? "xen-cdrom" : "xen-disk",
+                     &error_abort);
+        qemu_opt_set(devopts, "drive", qdict_get_str(bs_opts, "id"),
+                     &error_abort);
     }
 
     filename = qemu_opt_get(legacy_opts, "file");
diff --git a/hw/block/xen-block.c b/hw/block/xen-block.c
index a07cd7eb5d..f490b24ec8 100644
--- a/hw/block/xen-block.c
+++ b/hw/block/xen-block.c
@@ -27,6 +27,7 @@ 
 #include "sysemu/block-backend.h"
 #include "sysemu/iothread.h"
 #include "dataplane/xen-block.h"
+#include "hw/xen/interface/io/xs_wire.h"
 #include "trace.h"
 
 static char *xen_block_get_name(XenDevice *xendev, Error **errp)
@@ -34,6 +35,43 @@  static char *xen_block_get_name(XenDevice *xendev, Error **errp)
     XenBlockDevice *blockdev = XEN_BLOCK_DEVICE(xendev);
     XenBlockVdev *vdev = &blockdev->props.vdev;
 
+    if (blockdev->props.vdev.type == XEN_BLOCK_VDEV_TYPE_INVALID) {
+        XenBus *xenbus = XEN_BUS(qdev_get_parent_bus(DEVICE(xendev)));
+        char fe_path[XENSTORE_ABS_PATH_MAX + 1];
+        char *value;
+        int disk = 0;
+        unsigned long idx;
+
+        /* Find an unoccupied device name */
+        while (disk < (1 << 20)) {
+            if (disk < (1 << 4)) {
+                idx = (202 << 8) | (disk << 4);
+            } else {
+                idx = (1 << 28) | (disk << 8);
+            }
+            snprintf(fe_path, sizeof(fe_path),
+                     "/local/domain/%u/device/vbd/%lu",
+                     xendev->frontend_id, idx);
+            value = qemu_xen_xs_read(xenbus->xsh, XBT_NULL, fe_path, NULL);
+            if (!value) {
+                if (errno == ENOENT) {
+                    vdev->type = XEN_BLOCK_VDEV_TYPE_XVD;
+                    vdev->partition = 0;
+                    vdev->disk = disk;
+                    vdev->number = idx;
+                    goto found;
+                }
+                error_setg(errp, "cannot read %s: %s", fe_path,
+                           strerror(errno));
+                return NULL;
+            }
+            free(value);
+            disk++;
+        }
+        error_setg(errp, "cannot find device vdev for block device");
+        return NULL;
+    }
+ found:
     return g_strdup_printf("%lu", vdev->number);
 }
 
diff --git a/hw/xen/xen_devconfig.c b/hw/xen/xen_devconfig.c
index 9b7304e544..3f77c675c6 100644
--- a/hw/xen/xen_devconfig.c
+++ b/hw/xen/xen_devconfig.c
@@ -46,34 +46,6 @@  static int xen_config_dev_all(char *fe, char *be)
 
 /* ------------------------------------------------------------- */
 
-int xen_config_dev_blk(DriveInfo *disk)
-{
-    char fe[256], be[256], device_name[32];
-    int vdev = 202 * 256 + 16 * disk->unit;
-    int cdrom = disk->media_cd;
-    const char *devtype = cdrom ? "cdrom" : "disk";
-    const char *mode    = cdrom ? "r"     : "w";
-    const char *filename = qemu_opt_get(disk->opts, "file");
-
-    snprintf(device_name, sizeof(device_name), "xvd%c", 'a' + disk->unit);
-    xen_pv_printf(NULL, 1, "config disk %d [%s]: %s\n",
-                  disk->unit, device_name, filename);
-    xen_config_dev_dirs("vbd", "qdisk", vdev, fe, be, sizeof(fe));
-
-    /* frontend */
-    xenstore_write_int(fe, "virtual-device",  vdev);
-    xenstore_write_str(fe, "device-type",     devtype);
-
-    /* backend */
-    xenstore_write_str(be, "dev",             device_name);
-    xenstore_write_str(be, "type",            "file");
-    xenstore_write_str(be, "params",          filename);
-    xenstore_write_str(be, "mode",            mode);
-
-    /* common stuff */
-    return xen_config_dev_all(fe, be);
-}
-
 int xen_config_dev_nic(NICInfo *nic)
 {
     char fe[256], be[256];
diff --git a/hw/xenpv/xen_machine_pv.c b/hw/xenpv/xen_machine_pv.c
index 17cda5ec13..1533f5dfb4 100644
--- a/hw/xenpv/xen_machine_pv.c
+++ b/hw/xenpv/xen_machine_pv.c
@@ -32,7 +32,6 @@ 
 
 static void xen_init_pv(MachineState *machine)
 {
-    DriveInfo *dinfo;
     int i;
 
     setup_xen_backend_ops();
@@ -64,14 +63,6 @@  static void xen_init_pv(MachineState *machine)
         vga_interface_created = true;
     }
 
-    /* configure disks */
-    for (i = 0; i < 16; i++) {
-        dinfo = drive_get(IF_XEN, 0, i);
-        if (!dinfo)
-            continue;
-        xen_config_dev_blk(dinfo);
-    }
-
     /* configure nics */
     for (i = 0; i < nb_nics; i++) {
         if (!nd_table[i].model || 0 != strcmp(nd_table[i].model, "xen"))
diff --git a/include/hw/xen/xen-legacy-backend.h b/include/hw/xen/xen-legacy-backend.h
index 6c307c5f2c..fc42146bc2 100644
--- a/include/hw/xen/xen-legacy-backend.h
+++ b/include/hw/xen/xen-legacy-backend.h
@@ -81,7 +81,6 @@  extern struct XenDevOps xen_usb_ops;          /* xen-usb.c         */
 
 /* configuration (aka xenbus setup) */
 void xen_config_cleanup(void);
-int xen_config_dev_blk(DriveInfo *disk);
 int xen_config_dev_nic(NICInfo *nic);
 int xen_config_dev_vfb(int vdev, const char *type);
 int xen_config_dev_vkbd(int vdev);