Re: [PATCH 0/3]: x86, fpu: unlazy_fpu fixes/cleanups

[Dave Hansen]

On 01/29/2015 05:33 PM, Rik van Riel wrote:
>> > Hmm, if the the thread was not using the FPU, and this fails to
>> > save anything in to the xsave_buf, what will bndcsr point to?
> If the thread was not using the FPU, can we reach the
> bound range exception?
> 
> I believe the MPX feature uses information in the xstate.

There are really two kinds of bounds exceptions.  There is an "old"
'BOUND' instruction that will generate #BR's as well as the new MPX
instructions.  The new ones require xstate and poking the FPU, etc...
The old one did not.

So, we _can_ as far as I know get in to do_bounds() without using the FPU.
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