[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] drive_del vs. device_del: what should come first?
From: |
Markus Armbruster |
Subject: |
Re: [Qemu-devel] drive_del vs. device_del: what should come first? |
Date: |
Tue, 01 Apr 2014 17:48:27 +0200 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/24.2 (gnu/linux) |
Heinz Graalfs <address@hidden> writes:
> Hi Kevin,
>
> doing a
>
> virsh detach-device ...
>
> ends up in the following QEMU monitor commands:
>
> 1. device_del ...
> 2. drive_del ...
>
> qmp_device_del() performs the device unplug path.
> In case of a block device do_drive_del() tries to
> prevent further IO against the host device.
>
> However, bdrv_find() during drive_del() results in
> an error, because the device is already gone. Due to
> this error all the bdrv_xxx calls to quiesce the block
> driver as well as all other processing is skipped.
>
> Is the sequence that libvirt triggers OK?
> Shouldn't drive_del be executed first?
No.
drive_del is nasty. Its purpose is to revoke access to an image even
when the guest refuses to cooperate. To the guest, this looks like
hardware failure.
If you drive_del before device_del, even a perfectly well-behaved guest
guest is exposed to a terminally broken device between drive_del and
completion of unplug.
Always try a device_del first, and only if that does not complete within
reasonable time, and you absolutely must revoke access to the image,
then whack it over the head with drive_del.
- [Qemu-devel] drive_del vs. device_del: what should come first?, Heinz Graalfs, 2014/04/01
- Re: [Qemu-devel] drive_del vs. device_del: what should come first?,
Markus Armbruster <=
- Re: [Qemu-devel] drive_del vs. device_del: what should come first?, Heinz Graalfs, 2014/04/02
- Re: [Qemu-devel] drive_del vs. device_del: what should come first?, Markus Armbruster, 2014/04/02
- Re: [Qemu-devel] drive_del vs. device_del: what should come first?, Heinz Graalfs, 2014/04/03
- Re: [Qemu-devel] drive_del vs. device_del: what should come first?, Heinz Graalfs, 2014/04/11
- Re: [Qemu-devel] drive_del vs. device_del: what should come first?, Stefan Hajnoczi, 2014/04/23
- Re: [Qemu-devel] drive_del vs. device_del: what should come first?, Heinz Graalfs, 2014/04/25