[Qemu-devel] Re: [PATCH 1/2] Implement drive_del to decouple block removal from device removal

[Kevin Wolf]

Am 12.11.2010 16:38, schrieb Ryan Harper:
> 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 <address@hidden>
> ---
>  blockdev.c      |   39 +++++++++++++++++++++++++++++++++++++++
>  blockdev.h      |    1 +
>  hmp-commands.hx |   18 ++++++++++++++++++
>  3 files changed, 58 insertions(+), 0 deletions(-)
> 
> diff --git a/blockdev.c b/blockdev.c
> index 6cb179a..f6ac439 100644
> --- a/blockdev.c
> +++ b/blockdev.c
> @@ -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;
> +}
> diff --git a/blockdev.h b/blockdev.h
> index 653affc..2a0559e 100644
> --- a/blockdev.h
> +++ b/blockdev.h
> @@ -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
> diff --git a/hmp-commands.hx b/hmp-commands.hx
> index e5585ba..d6dc18c 100644
> --- a/hmp-commands.hx
> +++ b/hmp-commands.hx
> @@ -68,6 +68,24 @@ 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
> address@hidden delete @var{device}
> address@hidden delete

I think this should be @item drive_del and @findex drive_del.

Kevin