[PATCH v3 13/28] hw/xen: automatically assign device index to block devices

David Woodhouse
2023-10-25T14:51:41Z

From: David Woodhouse <dwmw@amazon.co.uk>

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 <dwmw@amazon.co.uk>
Acked-by: Kevin Wolf <kwolf@redhat.com>
---
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(-)

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 64470fc579..5011fe9430 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);
--
2.40.1