Re: [PATCH v2] xen: arm: process XENMEM_add_to_physmap_range forwards not backwards.

[George Dunlap <george.dunlap@eu.citrix.com>]

On 12/18/2013 01:39 PM, Ian Campbell wrote:
> Jan points out that processing the list backwards is rather counter intuitive
> and that the effect of the hypercall can differ between forwards and backwards
> processing (e.g. in the presence of duplicate idx or gpfn, which would be
> unusualy but as Jan says, users are a creative bunch)
>
> Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
> Cc: Jan Beulich <JBeulich@suse.com>
> Cc: Mukesh Rathor <mukesh.rathor@oracle.com>
> ---
> v2: Remember to crank the errs array too.
>
>      Resending despite abuse of overwriting the IN paramters, since coming to
>      rely on backwards processing is a harder hole to get out of than going
>      from modifying the strict to not.
>
> Release: subtle ABI change, should go in to 4.4 before people rely on it (they
> are not relying on it today TTBOMK and it seems unlikely but lets not risk it)

Yes, I agree: the risk of having to work around a bad ABI indefinitely 
is worse than the relatively small risk of finding a bug in this and 
then fixing it.

Release-acked-by: George Dunlap <george.dunlap@eu.citrix.com>

  -George