Re: [Qemu-devel] fw cfg files cross-version migration races

[Gabriel L. Somlo]

On Mon, Jun 08, 2015 at 01:44:18PM +0200, Paolo Bonzini wrote:
> 
> 
> On 08/06/2015 13:19, Gerd Hoffmann wrote:
> >>> I would simply sort everything (and do it for new machine types only,
> >                                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> >>> for backward compatibility reasons).  Sorting user-provided blobs only
> >>> adds complexity for no reason.
> > 
> >> Do we want this for all machine types, or only for new ones?
> 
> I think it is not backwards compatible: sorting names changes the fw_cfg
> ids of the files, and hence the guest ABI.

I'm wonderingjust when exactly to start sorting items in fw_cfg ? 

Different machine types insert different blobs at various points
during their initialization (and possibly on-demand during hot-plug
events, I'm not 100% sure).

So when exactly can we know that "we now have everything, it's time to
start sorting" ?

I'm also assuming this applies to named (file) entries only, and the
unnamed entries (with "indices" in the "table" < FW_CFG_FILE_DIR) will
not have to be sorted.

Thanks,
--Gabriel