linux-kernel - xsaves support broken?

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Message-ID: <54F4F964.5030701@intel.com>
Date:	Mon, 02 Mar 2015 15:59:32 -0800
From:	Dave Hansen <dave.hansen@...el.com>
To:	LKML <linux-kernel@...r.kernel.org>,
	the arch/x86 maintainers <x86@...nel.org>,
	"Yu, Fenghua" <fenghua.yu@...el.com>
Subject: xsaves support broken?

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
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