Re: [Qemu-devel] [PATCH] qdev: DEVICE_DELETED event

[Eric Blake <eblake@redhat.com>]

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On 03/06/2013 06:00 AM, Michael S. Tsirkin wrote:
> libvirt has a long-standing bug: when removing the device,
> it can request removal but does not know when does the
> removal complete. Add an event so we can fix this in a robust way.

s/complete/completes/

> 
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> 
> diff --git a/QMP/qmp-events.txt b/QMP/qmp-events.txt
> index b2698e4..ec5b810 100644
> --- a/QMP/qmp-events.txt
> +++ b/QMP/qmp-events.txt
> @@ -136,6 +136,21 @@ Example:
>  Note: The "ready to complete" status is always reset by a BLOCK_JOB_ERROR
>  event.
> 
> +DEVICE_DELETED
> +-----------------
> +
> +It's emitted whenever the device removal completion is acknowledged

I know this is copy-and-paste from DEVICE_TRAY_MOVED, but most of the
file uses the more succinct: s/It's emitted/Emitted/

> +by the guest. At this point, it's safe to reuse the specified device ID.
> +Device removal can be initiated by the guest or by HMP/QMP commands.
> +
> +Data:
> +
> +- "device": device name (json-string)
> +
> +{ "event": "DEVICE_DELETED",
> +  "data": { "device": "virtio-net-pci-0" },
> +  "timestamp": { "seconds": 1265044230, "microseconds": 450486 } }

Long overdue!
> +++ b/qapi-schema.json
> @@ -2354,7 +2354,9 @@
>  # Notes: When this command completes, the device may not be removed from the
>  #        guest.  Hot removal is an operation that requires guest cooperation.
>  #        This command merely requests that the guest begin the hot removal
> -#        process.
> +#        process.  Completion of the device removal process is signaled with a
> +#        DEVICE_DELETED event. Guest reset will automatically complete removal
> +#        for all devices.

Question - if libvirt misses the event (for example, if libvirtd
requests a remove, but then gets restarted, and the event arrives before
libvirtd is back up), is there a way to poll whether the the removal has
completed?  The event is great to minimize polling overhead in the
common case, but we generally provide this sort of information via a
pollable interface at the same time.

>  #
>  # Since: 0.14.0
>  ##
> ---
>  QMP/qmp-events.txt        | 15 +++++++++++++++
>  hw/qdev.c                 |  6 ++++++
>  include/monitor/monitor.h |  1 +
>  monitor.c                 |  1 +
>  qapi-schema.json          |  4 +++-
>  5 files changed, 26 insertions(+), 1 deletion(-)

Looks like your patch body is included twice?

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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