RE: xsaves support broken?

[Yu, Fenghua]

> From: Hansen, Dave
> Sent: Monday, March 02, 2015 4:00 PM
> 
> Hi Fenghua,
> 
> I was testing some new MPX code, and realized that MPX had stopped
> working completely.  The prctl() failed to turn it on, which I tracked down to a
> 0 in "BNDCSR" where we expected to see an enable bit.
> 
> I realized that I had managed to remove the "noxsaves" boot option from my
> kernel.  Re-adding "noxsaves" made MPX work again, and the BNDCSR
> contents were properly passed in to the kernel.
> 
> Is it possible that  "xsaves" use inside the kernel is simply broken?
> 
> Config is here:
> 
> 	http://sr71.net/~dave/intel/config-20150302

Xsaves has been tested by QA since 3.17 with or without MPX. I'm not aware of reported issues.

But MPX is the only code to call the get_xsave_addr kernel API. Though it has been tested before on upstream MPX code.

What changes in your new MPX code?

Thanks.

-Fenghua