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Date: Wed, 3 Jun 2015 18:03:05 +0200
From: "Michael S. Tsirkin" <mst@redhat.com>
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In-Reply-To: <1433229074.1637.7.camel@nilsson.home.kraxel.org>
Subject: Re: [Qemu-devel] fw cfg files cross-version migration races
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To: Gerd Hoffmann <kraxel@redhat.com>
Cc: "Gabriel L. Somlo" <somlo@cmu.edu>, qemu-devel@nongnu.org, "Gabriel L. Somlo" <gsomlo@gmail.com>, pbonzini@redhat.com, lersek@redhat.com

On Tue, Jun 02, 2015 at 09:11:14AM +0200, Gerd Hoffmann wrote:
>   Hi,
> 
> > I guess the only reason this isn't a problem is that nobody currently
> > attempts to access fw_cfg after a migration ? :)
> 
> Accessing fw_cfg after migration is fine.  Problem is this ...
> 
>   (1) read directory
>   (2) migrate
>   (3) read file
> 
> ... in case the file ordering happens to be different on the destination
> host due to initialization order changes.
> 
> So, sorting entries (and the index assigned too) should fix this, right?
> That looks easiest to me.
> 
> cheers,
>   Gerd

Right. The only issue is we are introducing a breakage even if
there was otherwise no reason for it otherwise.
I'll let you make the decision.

-- 
MST