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From: Juan Quintela <quintela@redhat.com>
In-Reply-To: <4EC11D0A.3060703@us.ibm.com> (Anthony Liguori's message of "Mon,
	14 Nov 2011 07:52:10 -0600")
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Date: Mon, 14 Nov 2011 20:52:56 +0100
Message-ID: <m3d3cuwkfb.fsf@trasno.mitica>
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Subject: Re: [Qemu-devel] [PATCH 2/7] ivshmem: use migration blockers to
	prevent live	migration in peer mode
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To: Anthony Liguori <aliguori@us.ibm.com>
Cc: Kevin Wolf <kwolf@redhat.com>, Lucas Meneghel Rodrigues <lmr@redhat.com>, Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>, qemu-devel@nongnu.org, Avi Kivity <avi@redhat.com>

Anthony Liguori <aliguori@us.ibm.com> wrote:
> On 11/14/2011 07:05 AM, Juan Quintela wrote:
>> Anthony Liguori<aliguori@us.ibm.com>  wrote:
>>> Now when you try to migrate with ivshmem, you get a proper QMP error:
>>>
>>> (qemu) migrate tcp:localhost:1025
>>> Migration is disabled when using feature 'peer mode' in device 'ivshmem'
>>> (qemu)
>>
>> This was the only user of register_device_unmigratable(), just to remove
>> function if we continue this path.
>
> There are a couple more in usb also but I can convert them too.

usb uses "yet another" way to make devices unmigratable.

static const VMStateDescription vmstate_usb_host = {
    .name = "usb-host",
    .unmigratable = 1,
};

So, we have "already" two ways to make a device unmigratable:
- calling register_device_unmigratable() (ivhs)
- definining in vmstate .unmigratable = 1
- and now your new way.

My point was that only one (or even two) should be enough.

Why two? because the .unmigratable way is very useful for devices that
haven't been made "migratable", but that are converted to qdev.  Not
jthat this couldn't be "fixed" on registration with a call to
migrate_add_blocker.

Later, Juan.