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Implement drive_del to decouple block removal from device removal

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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
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18
hmp-commands.hx
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@ -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
{