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Date: Sun, 14 Nov 2010 12:11:05 +0200
From: "Michael S. Tsirkin" <mst@redhat.com>
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Subject: [Qemu-devel] Re: Cannot not unplug cold-plugged devices
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To: Isaku Yamahata <yamahata@valinux.co.jp>
Cc: Cam Macdonell <cam@cs.ualberta.ca>, "qemu-devel@nongnu.org Developers" <qemu-devel@nongnu.org>

On Sun, Nov 14, 2010 at 11:57:52AM +0900, Isaku Yamahata wrote:
> On Sat, Nov 13, 2010 at 10:59:15PM +0200, Michael S. Tsirkin wrote:
> > On Fri, Nov 12, 2010 at 09:50:30PM +0900, Isaku Yamahata wrote:
> > > On Fri, Nov 12, 2010 at 01:26:30PM +0200, Michael S. Tsirkin wrote:
> > > > No, I am just trying to understand why is hotplug event dangerous.
> > > > We still get it if we do device add before starting the VM, right?
> > > 
> > > I'm not sure if it's safe to call enable/disable_device() and
> > > pm_update_sci() before starting VM.
> > > So I'd like to avoid to call them instead of making sure it.
> > > If someone else ensures its safety, I'm willing to eliminate the if clause.
> > 
> > Well I don't think it's dangerous.
> 
> Why?

Because the same effect can be achieved by starting qemu with vm
stopped, adding device, then starting qemu.

> > I guess it makes sense for whatever is supplied on qemu command line
> > to not cause a hotplug event.
> 
> But, those functions inject a hot plug event into a guest.

That's why I think your patch is correct. Just the comment is
a bit misleading in saying it's dangerous.
It's just more correct without the event.

> -- 
> yamahata