[Qemu-devel] [PATCH 0/2] v8 Decouple block device removal from device removal

[Qemu-devel] [PATCH 0/2] v8 Decouple block device removal from device removal

[Ryan Harper]

details, details, v8

This patch series decouples the detachment of a block device from the
removal of the backing pci-device.  Removal of a hotplugged pci device
requires the guest to respond before qemu tears down the block device.
In some cases, the guest may not respond leaving the guest with
continued access to the block device.  Mgmt layer doesn't have a
reliable method to force a disconnect.  

The new monitor command, drive_del, will revoke a guests access to the
block device independently of the removal of the pci device.

The first patch implements drive_del, the second patch implements the
qmp version of the monitor command.

Changes since v7:
- Fixed up doc strings (delete -> drive_del)
Changes since v6:
- Updated patch description
- Dropped bdrv_unplug and inlined in drive_del
- Explicitly invoke drive_uninit()
Changes since v5:
- Removed dangling pointers in guest and host state.  This ensures things like 
  info block no longer displays the deleted drive; though info pci will
  continue to display the pci device until the guest responds to the removal
  request.
- Renamed drive_unplug -> drive_del
Changes since v4:
- Droppped drive_get_by_id patch and use bdrv_find() instead
- Added additional details about drive_unplug to hmp/qmp interface

Changes since v3:
- Moved QMP command for drive_unplug() to separate patch

Changes since v2:
- Added QMP command for drive_unplug()

Changes since v1:
- CodingStyle fixes
- Added qemu_aio_flush() to bdrv_unplug()

Signed-off-by: Ryan Harper <ryanh@us.ibm.com>

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

[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 <ryanh@us.ibm.com>
---
 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..c8b0206 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
+@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
+
+    {
         .name       = "change",
         .args_type  = "device:B,target:F,arg:s?",
         .params     = "device filename [format]",
-- 
1.6.3.3

[Qemu-devel] [PATCH 2/2] Add qmp version of drive_del

[Ryan Harper]

Signed-off-by: Ryan Harper <ryanh@us.ibm.com>
---
 qmp-commands.hx |   29 +++++++++++++++++++++++++++++
 1 files changed, 29 insertions(+), 0 deletions(-)

diff --git a/qmp-commands.hx b/qmp-commands.hx
index 793cf1c..1e0d4e9 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -338,6 +338,35 @@ Example:
 EQMP
 
     {
+        .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,
+    },
+
+SQMP
+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.
+
+Arguments:
+
+- "id": the device's ID (json-string)
+
+Example:
+
+-> { "execute": "drive_del", "arguments": { "id": "drive-virtio-blk1" } }
+<- { "return": {} }
+
+EQMP
+
+    {
         .name       = "cpu",
         .args_type  = "index:i",
         .params     = "index",
-- 
1.6.3.3

[Qemu-devel] Re: [PATCH 0/2] v8 Decouple block device removal from device removal

[Kevin Wolf]

Am 12.11.2010 18:07, schrieb Ryan Harper:
> details, details, v8
> 
> This patch series decouples the detachment of a block device from the
> removal of the backing pci-device.  Removal of a hotplugged pci device
> requires the guest to respond before qemu tears down the block device.
> In some cases, the guest may not respond leaving the guest with
> continued access to the block device.  Mgmt layer doesn't have a
> reliable method to force a disconnect.  
> 
> The new monitor command, drive_del, will revoke a guests access to the
> block device independently of the removal of the pci device.
> 
> The first patch implements drive_del, the second patch implements the
> qmp version of the monitor command.
> 
> Changes since v7:
> - Fixed up doc strings (delete -> drive_del)
> Changes since v6:
> - Updated patch description
> - Dropped bdrv_unplug and inlined in drive_del
> - Explicitly invoke drive_uninit()
> Changes since v5:
> - Removed dangling pointers in guest and host state.  This ensures things like 
>   info block no longer displays the deleted drive; though info pci will
>   continue to display the pci device until the guest responds to the removal
>   request.
> - Renamed drive_unplug -> drive_del
> Changes since v4:
> - Droppped drive_get_by_id patch and use bdrv_find() instead
> - Added additional details about drive_unplug to hmp/qmp interface
> 
> Changes since v3:
> - Moved QMP command for drive_unplug() to separate patch
> 
> Changes since v2:
> - Added QMP command for drive_unplug()
> 
> Changes since v1:
> - CodingStyle fixes
> - Added qemu_aio_flush() to bdrv_unplug()
> 
> Signed-off-by: Ryan Harper <ryanh@us.ibm.com>

Thanks, applied both to the block branch.

Kevin

Re: [Qemu-devel] Re: [PATCH 0/2] v8 Decouple block device removal from device removal

[Luiz Capitulino]

On Fri, 12 Nov 2010 18:38:57 +0100
Kevin Wolf <kwolf@redhat.com> wrote:

> Am 12.11.2010 18:07, schrieb Ryan Harper:
> > details, details, v8
> > 
> > This patch series decouples the detachment of a block device from the
> > removal of the backing pci-device.  Removal of a hotplugged pci device
> > requires the guest to respond before qemu tears down the block device.
> > In some cases, the guest may not respond leaving the guest with
> > continued access to the block device.  Mgmt layer doesn't have a
> > reliable method to force a disconnect.  
> > 
> > The new monitor command, drive_del, will revoke a guests access to the
> > block device independently of the removal of the pci device.
> > 
> > The first patch implements drive_del, the second patch implements the
> > qmp version of the monitor command.
> > 
> > Changes since v7:
> > - Fixed up doc strings (delete -> drive_del)
> > Changes since v6:
> > - Updated patch description
> > - Dropped bdrv_unplug and inlined in drive_del
> > - Explicitly invoke drive_uninit()
> > Changes since v5:
> > - Removed dangling pointers in guest and host state.  This ensures things like 
> >   info block no longer displays the deleted drive; though info pci will
> >   continue to display the pci device until the guest responds to the removal
> >   request.
> > - Renamed drive_unplug -> drive_del
> > Changes since v4:
> > - Droppped drive_get_by_id patch and use bdrv_find() instead
> > - Added additional details about drive_unplug to hmp/qmp interface
> > 
> > Changes since v3:
> > - Moved QMP command for drive_unplug() to separate patch
> > 
> > Changes since v2:
> > - Added QMP command for drive_unplug()
> > 
> > Changes since v1:
> > - CodingStyle fixes
> > - Added qemu_aio_flush() to bdrv_unplug()
> > 
> > Signed-off-by: Ryan Harper <ryanh@us.ibm.com>
> 
> Thanks, applied both to the block branch.

I guess the conclusion was that we don't want the new command
in QMP?

  http://lists.gnu.org/archive/html/qemu-devel/2010-11/msg01084.html

Re: [Qemu-devel] Re: [PATCH 0/2] v8 Decouple block device removal from device removal

[Kevin Wolf]

Am 16.11.2010 14:51, schrieb Luiz Capitulino:
> On Fri, 12 Nov 2010 18:38:57 +0100
> Kevin Wolf <kwolf@redhat.com> wrote:
> 
>> Am 12.11.2010 18:07, schrieb Ryan Harper:
>>> details, details, v8
>>>
>>> This patch series decouples the detachment of a block device from the
>>> removal of the backing pci-device.  Removal of a hotplugged pci device
>>> requires the guest to respond before qemu tears down the block device.
>>> In some cases, the guest may not respond leaving the guest with
>>> continued access to the block device.  Mgmt layer doesn't have a
>>> reliable method to force a disconnect.  
>>>
>>> The new monitor command, drive_del, will revoke a guests access to the
>>> block device independently of the removal of the pci device.
>>>
>>> The first patch implements drive_del, the second patch implements the
>>> qmp version of the monitor command.
>>>
>>> Changes since v7:
>>> - Fixed up doc strings (delete -> drive_del)
>>> Changes since v6:
>>> - Updated patch description
>>> - Dropped bdrv_unplug and inlined in drive_del
>>> - Explicitly invoke drive_uninit()
>>> Changes since v5:
>>> - Removed dangling pointers in guest and host state.  This ensures things like 
>>>   info block no longer displays the deleted drive; though info pci will
>>>   continue to display the pci device until the guest responds to the removal
>>>   request.
>>> - Renamed drive_unplug -> drive_del
>>> Changes since v4:
>>> - Droppped drive_get_by_id patch and use bdrv_find() instead
>>> - Added additional details about drive_unplug to hmp/qmp interface
>>>
>>> Changes since v3:
>>> - Moved QMP command for drive_unplug() to separate patch
>>>
>>> Changes since v2:
>>> - Added QMP command for drive_unplug()
>>>
>>> Changes since v1:
>>> - CodingStyle fixes
>>> - Added qemu_aio_flush() to bdrv_unplug()
>>>
>>> Signed-off-by: Ryan Harper <ryanh@us.ibm.com>
>>
>> Thanks, applied both to the block branch.
> 
> I guess the conclusion was that we don't want the new command
> in QMP?
> 
>   http://lists.gnu.org/archive/html/qemu-devel/2010-11/msg01084.html

If you compare the time of these mails, Markus sent his mail only a few
minutes after I had applied the patches and posted this.

Ryan split the patch in two parts only to allow dropping the QMP part if
we decided so, so I think he'll agree. I'm going to drop the second
patch from my queue again before I send a pull request.

Kevin

Re: [Qemu-devel] Re: [PATCH 0/2] v8 Decouple block device removal from device removal

[Luiz Capitulino]

On Tue, 16 Nov 2010 15:01:12 +0100
Kevin Wolf <kwolf@redhat.com> wrote:

> Am 16.11.2010 14:51, schrieb Luiz Capitulino:
> > On Fri, 12 Nov 2010 18:38:57 +0100
> > Kevin Wolf <kwolf@redhat.com> wrote:
> > 
> >> Am 12.11.2010 18:07, schrieb Ryan Harper:
> >>> details, details, v8
> >>>
> >>> This patch series decouples the detachment of a block device from the
> >>> removal of the backing pci-device.  Removal of a hotplugged pci device
> >>> requires the guest to respond before qemu tears down the block device.
> >>> In some cases, the guest may not respond leaving the guest with
> >>> continued access to the block device.  Mgmt layer doesn't have a
> >>> reliable method to force a disconnect.  
> >>>
> >>> The new monitor command, drive_del, will revoke a guests access to the
> >>> block device independently of the removal of the pci device.
> >>>
> >>> The first patch implements drive_del, the second patch implements the
> >>> qmp version of the monitor command.
> >>>
> >>> Changes since v7:
> >>> - Fixed up doc strings (delete -> drive_del)
> >>> Changes since v6:
> >>> - Updated patch description
> >>> - Dropped bdrv_unplug and inlined in drive_del
> >>> - Explicitly invoke drive_uninit()
> >>> Changes since v5:
> >>> - Removed dangling pointers in guest and host state.  This ensures things like 
> >>>   info block no longer displays the deleted drive; though info pci will
> >>>   continue to display the pci device until the guest responds to the removal
> >>>   request.
> >>> - Renamed drive_unplug -> drive_del
> >>> Changes since v4:
> >>> - Droppped drive_get_by_id patch and use bdrv_find() instead
> >>> - Added additional details about drive_unplug to hmp/qmp interface
> >>>
> >>> Changes since v3:
> >>> - Moved QMP command for drive_unplug() to separate patch
> >>>
> >>> Changes since v2:
> >>> - Added QMP command for drive_unplug()
> >>>
> >>> Changes since v1:
> >>> - CodingStyle fixes
> >>> - Added qemu_aio_flush() to bdrv_unplug()
> >>>
> >>> Signed-off-by: Ryan Harper <ryanh@us.ibm.com>
> >>
> >> Thanks, applied both to the block branch.
> > 
> > I guess the conclusion was that we don't want the new command
> > in QMP?
> > 
> >   http://lists.gnu.org/archive/html/qemu-devel/2010-11/msg01084.html
> 
> If you compare the time of these mails, Markus sent his mail only a few
> minutes after I had applied the patches and posted this.

Oh, didn't notice that.

> Ryan split the patch in two parts only to allow dropping the QMP part if
> we decided so, so I think he'll agree. I'm going to drop the second
> patch from my queue again before I send a pull request.

Ok, thanks.

Re: [Qemu-devel] Re: [PATCH 0/2] v8 Decouple block device removal from device removal

[Ryan Harper]

* Kevin Wolf <kwolf@redhat.com> [2010-11-16 08:05]:
> Am 16.11.2010 14:51, schrieb Luiz Capitulino:
> > On Fri, 12 Nov 2010 18:38:57 +0100
> > Kevin Wolf <kwolf@redhat.com> wrote:
> > 
> >> Am 12.11.2010 18:07, schrieb Ryan Harper:
> >>> details, details, v8
> >>>
> >>> This patch series decouples the detachment of a block device from the
> >>> removal of the backing pci-device.  Removal of a hotplugged pci device
> >>> requires the guest to respond before qemu tears down the block device.
> >>> In some cases, the guest may not respond leaving the guest with
> >>> continued access to the block device.  Mgmt layer doesn't have a
> >>> reliable method to force a disconnect.  
> >>>
> >>> The new monitor command, drive_del, will revoke a guests access to the
> >>> block device independently of the removal of the pci device.
> >>>
> >>> The first patch implements drive_del, the second patch implements the
> >>> qmp version of the monitor command.
> >>>
> >>> Changes since v7:
> >>> - Fixed up doc strings (delete -> drive_del)
> >>> Changes since v6:
> >>> - Updated patch description
> >>> - Dropped bdrv_unplug and inlined in drive_del
> >>> - Explicitly invoke drive_uninit()
> >>> Changes since v5:
> >>> - Removed dangling pointers in guest and host state.  This ensures things like 
> >>>   info block no longer displays the deleted drive; though info pci will
> >>>   continue to display the pci device until the guest responds to the removal
> >>>   request.
> >>> - Renamed drive_unplug -> drive_del
> >>> Changes since v4:
> >>> - Droppped drive_get_by_id patch and use bdrv_find() instead
> >>> - Added additional details about drive_unplug to hmp/qmp interface
> >>>
> >>> Changes since v3:
> >>> - Moved QMP command for drive_unplug() to separate patch
> >>>
> >>> Changes since v2:
> >>> - Added QMP command for drive_unplug()
> >>>
> >>> Changes since v1:
> >>> - CodingStyle fixes
> >>> - Added qemu_aio_flush() to bdrv_unplug()
> >>>
> >>> Signed-off-by: Ryan Harper <ryanh@us.ibm.com>
> >>
> >> Thanks, applied both to the block branch.
> > 
> > I guess the conclusion was that we don't want the new command
> > in QMP?
> > 
> >   http://lists.gnu.org/archive/html/qemu-devel/2010-11/msg01084.html
> 
> If you compare the time of these mails, Markus sent his mail only a few
> minutes after I had applied the patches and posted this.
> 
> Ryan split the patch in two parts only to allow dropping the QMP part if
> we decided so, so I think he'll agree. I'm going to drop the second

Indeed.

> patch from my queue again before I send a pull request.
> 
> Kevin

-- 
Ryan Harper
Software Engineer; Linux Technology Center
IBM Corp., Austin, Tx
ryanh@us.ibm.com

[Qemu-devel] [PATCH 0/2] v7 Decouple block device removal from device removal

[Ryan Harper]

Once more dear friends, v7

This patch series decouples the detachment of a block device from the
removal of the backing pci-device.  Removal of a hotplugged pci device
requires the guest to respond before qemu tears down the block device.
In some cases, the guest may not respond leaving the guest with
continued access to the block device.  Mgmt layer doesn't have a
reliable method to force a disconnect.  

The new monitor command, drive_del, will revoke a guests access to the
block device independently of the removal of the pci device.

The first patch implements drive_del, the second patch implements the
qmp version of the monitor command.

Changes since v6:
- Updated patch description
- Dropped bdrv_unplug and inlined in drive_del
- Explicitly invoke drive_uninit()
Changes since v5:
- Removed dangling pointers in guest and host state.  This ensures things like 
  info block no longer displays the deleted drive; though info pci will
  continue to display the pci device until the guest responds to the removal
  request.
- Renamed drive_unplug -> drive_del
Changes since v4:
- Droppped drive_get_by_id patch and use bdrv_find() instead
- Added additional details about drive_unplug to hmp/qmp interface

Changes since v3:
- Moved QMP command for drive_unplug() to separate patch

Changes since v2:
- Added QMP command for drive_unplug()

Changes since v1:
- CodingStyle fixes
- Added qemu_aio_flush() to bdrv_unplug()

Signed-off-by: Ryan Harper <ryanh@us.ibm.com>

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

[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 <ryanh@us.ibm.com>
---
 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
+@item delete @var{device}
+@findex delete
+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
+
+    {
         .name       = "change",
         .args_type  = "device:B,target:F,arg:s?",
         .params     = "device filename [format]",
-- 
1.6.3.3

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

[Markus Armbruster]

Ryan Harper <ryanh@us.ibm.com> writes:

> 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>
> ---
>  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) {

Superfluous parenthesis around *ptr.  Not worth a respin; I've tormented
you enough ;)


> +                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
> +@item delete @var{device}
> +@findex delete
> +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
> +
> +    {
>          .name       = "change",
>          .args_type  = "device:B,target:F,arg:s?",
>          .params     = "device filename [format]",