Re: [PATCH 07/10] x86/xsaves: Fix init_fpstate.header.xcomp_bv

[Dave Hansen]

On 02/22/2016 10:59 AM, Yu-cheng Yu wrote:
> This actually does not apply to XSAVES as XSAVES uses optimization. After
> init, all components are in INIT and not MODIFIED state and will not be
> saved. There is no need of setting xcomp_bv except for bit 63 to indicate
> a compacted format.

I look at it this way: xcomp_bv tells you the format of the buffer
xstate_bv tells you which components of the buffer are valid (not in
init state).

As it stands, every kernel xcomp_bv value should be identical, since the
kernel buffer is always in the same state and XSAVES is always called
with the same Requested Feature BitMap (RFBM).

While I don't think this patch _hurts_ anything, I think it might be a
bit confusing.  Wouldn't it just be easier if *EVERY* xcomp_bv value was
the same?