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Commit b8be15d5 authored by Yu-cheng Yu's avatar Yu-cheng Yu Committed by Ingo Molnar
Browse files

x86/fpu/xstate: Re-enable XSAVES 



We did not handle XSAVES instructions correctly. There were issues in
converting between standard and compacted format when interfacing with
user-space. These issues have been corrected.

Add a WARN_ONCE() to make it clear that XSAVES supervisor states are not
yet implemented.

Signed-off-by: default avatarYu-cheng Yu <yu-cheng.yu@intel.com>
Signed-off-by: default avatarFenghua Yu <fenghua.yu@intel.com>
Reviewed-by: default avatarDave Hansen <dave.hansen@intel.com>
Cc: H. Peter Anvin <h.peter.anvin@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi V Shankar <ravi.v.shankar@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1468253937-40008-5-git-send-email-fenghua.yu@intel.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 35ac2d7b

arch/x86/kernel/fpu/init.c

+0 −15
Original line number Diff line number Diff line
@@ -230,21 +230,6 @@ static void __init fpu__init_system_xstate_size_legacy(void) 
	}



	fpu_user_xstate_size = fpu_kernel_xstate_size;



	/*

	 * Quirk: we don't yet handle the XSAVES* instructions

	 * correctly, as we don't correctly convert between

	 * standard and compacted format when interfacing

	 * with user-space - so disable it for now.

	 *

	 * The difference is small: with recent CPUs the

	 * compacted format is only marginally smaller than

	 * the standard FPU state format.

	 *

	 * ( This is easy to backport while we are fixing

	 *   XSAVES* support. )

	 */

	setup_clear_cpu_cap(X86_FEATURE_XSAVES);

}



/*

arch/x86/kernel/fpu/xstate.c

+9 −0
Original line number Diff line number Diff line
@@ -221,6 +221,15 @@ void fpu__init_cpu_xstate(void) 
{

	if (!boot_cpu_has(X86_FEATURE_XSAVE) || !xfeatures_mask)

		return;

	/*

	 * Make it clear that XSAVES supervisor states are not yet

	 * implemented should anyone expect it to work by changing

	 * bits in XFEATURE_MASK_* macros and XCR0.

	 */

	WARN_ONCE((xfeatures_mask & XFEATURE_MASK_SUPERVISOR),

		"x86/fpu: XSAVES supervisor states are not yet implemented.\n");



	xfeatures_mask &= ~XFEATURE_MASK_SUPERVISOR;



	cr4_set_bits(X86_CR4_OSXSAVE);

	xsetbv(XCR_XFEATURE_ENABLED_MASK, xfeatures_mask);