Re: [PATCH v2 8/8] x86/msr: Drop compatibility #GP handling in guest_{rd,wr}msr()

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Fri, Aug 28, 2020 at 10:55:29AM +0200, Jan Beulich wrote:
> On 20.08.2020 17:08, Roger Pau Monne wrote:
> > Now that the main PV/HVM MSR handlers raise #GP for all unknown MSRs, there 
> > is
> > no need to special case these MSRs any more.
> 
> I agree, yet I'd like to point out (based on past backporting of
> security fixes) that this change may end up being a good source
> of backporting mistakes, as 4.14 may need chunks added here which
> on master / staging have no place anymore.

Even if we leave this chunk out, patches for > 4.14 won't need to add
anything to make a MSR return a #GP, so it's likely that the chunk
will have to be added for backports anyway.

I really have no idea of how to help with backporting with such change
in place.

Thanks, Roger.