Commit 9063f814 authored by Ryan Harper's avatar Ryan Harper Committed by Kevin Wolf
Browse files

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: default avatarRyan Harper <ryanh@us.ibm.com>
Signed-off-by: default avatarKevin Wolf <kwolf@redhat.com>
parent 6fa2c95f

blockdev.c

+39 −0
Original line number Diff line number Diff line
@@ -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;

}

blockdev.h

+1 −0
Original line number Diff line number Diff line
@@ -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

hmp-commands.hx

+18 −0
Original line number Diff line number Diff line
@@ -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



    {