Re: Rethinking sigcontext's xfeatures slightly for PKRU's benefit?

[Dave Hansen]

On 12/21/2015 02:52 PM, Andy Lutomirski wrote:
> Perhaps this is silly, but what if the default were changed to deny
> reads and writes for unallocated keys?  Is there a use case that
> breaks?

It's probably a reasonable debugging feature.

But, anything that takes an XSAVE feature out of its "init state" has
the potential to do a bit of harm because it increases the potential
size of writes during XSAVE.  XSAVEOPT will _help_ here, but we probably
don't want to go out of our way to take things out of the init state
when we're unsure of the benefits.
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