Implement drive_del to decouple block removal from device removal

Currently device hotplug removal code is tied to device removal via
ACPI.  All pci devices that are removable via device_del() require the
guest to respond to the request.  In some cases the guest may not
respond leaving the device still accessible to the guest.  The management
layer doesn't currently have a reliable way to revoke access to host
resource in the presence of an uncooperative guest.

This patch implements a new monitor command, drive_del, which
provides an explicit command to revoke access to a host block device.

drive_del first quiesces the block device (qemu_aio_flush;
bdrv_flush() and bdrv_close()).  This prevents further IO from being
submitted against the host device.  Finally, drive_del cleans up
pointers between the drive object (host resource) and the device
object (guest resource).

Signed-off-by: Ryan Harper <ryanh@us.ibm.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Ryan Harper 2010-11-12 11:07:13 -06:00 committed by Kevin Wolf
parent 6fa2c95f27
commit 9063f81415
3 changed files with 58 additions and 0 deletions

View file

@ -14,6 +14,8 @@
#include "qemu-option.h"
#include "qemu-config.h"
#include "sysemu.h"
#include "hw/qdev.h"
#include "block_int.h"
static QTAILQ_HEAD(drivelist, DriveInfo) drives = QTAILQ_HEAD_INITIALIZER(drives);
@ -597,3 +599,40 @@ int do_change_block(Monitor *mon, const char *device,
}
return monitor_read_bdrv_key_start(mon, bs, NULL, NULL);
}
int do_drive_del(Monitor *mon, const QDict *qdict, QObject **ret_data)
{
const char *id = qdict_get_str(qdict, "id");
BlockDriverState *bs;
BlockDriverState **ptr;
Property *prop;
bs = bdrv_find(id);
if (!bs) {
qerror_report(QERR_DEVICE_NOT_FOUND, id);
return -1;
}
/* quiesce block driver; prevent further io */
qemu_aio_flush();
bdrv_flush(bs);
bdrv_close(bs);
/* clean up guest state from pointing to host resource by
* finding and removing DeviceState "drive" property */
for (prop = bs->peer->info->props; prop && prop->name; prop++) {
if (prop->info->type == PROP_TYPE_DRIVE) {
ptr = qdev_get_prop_ptr(bs->peer, prop);
if ((*ptr) == bs) {
bdrv_detach(bs, bs->peer);
*ptr = NULL;
break;
}
}
}
/* clean up host side */
drive_uninit(drive_get_by_blockdev(bs));
return 0;
}

View file

@ -51,5 +51,6 @@ int do_eject(Monitor *mon, const QDict *qdict, QObject **ret_data);
int do_block_set_passwd(Monitor *mon, const QDict *qdict, QObject **ret_data);
int do_change_block(Monitor *mon, const char *device,
const char *filename, const char *fmt);
int do_drive_del(Monitor *mon, const QDict *qdict, QObject **ret_data);
#endif

View file

@ -65,6 +65,24 @@ STEXI
@item eject [-f] @var{device}
@findex eject
Eject a removable medium (use -f to force it).
ETEXI
{
.name = "drive_del",
.args_type = "id:s",
.params = "device",
.help = "remove host block device",
.user_print = monitor_user_noop,
.mhandler.cmd_new = do_drive_del,
},
STEXI
@item drive_del @var{device}
@findex drive_del
Remove host block device. The result is that guest generated IO is no longer
submitted against the host device underlying the disk. Once a drive has
been deleted, the QEMU Block layer returns -EIO which results in IO
errors in the guest for applications that are reading/writing to the device.
ETEXI
{