[CRIU] [PATCH 06/15] cpuinfo: x86 -- Add dump and validation

[Cyrill Gorcunov]

On Tue, Sep 23, 2014 at 11:07:01PM +0400, Pavel Emelyanov wrote:
> 
> OK. Let's imagine the cpu has 
> 
>    X86_FEATURE_XMM4_1 | X86_FEATURE_XMM4_2 | A
> 
> and we ask it to check the image which contains 
> 
>    X86_FEATURE_XMM4_1 | B
> 
> and let's assume that A == B. Will the checker fail? Should it? Why?

Sure it fails, and sure more precise feature deps inspection is needed
but as first iteration I think it's fine having plain memcmp here.
As to should it -- I don't know, technically the cpu itself is
backward compatible (at least it should be) but if someone migrate
to feature rich cpu , the dump it here and migrate back -- he will
have unpleasant surprise in restore failure and will have to pass
--cpu-cap none or something to ignore new feature mask obtained
from remote cpu. Thus lets require complete match for feature bits
and relax it in future if needed.