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x86/fpu/xstate: Re-enable XSAVES

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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: Yu-cheng Yu <yu-cheng.yu@intel.com>
Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Reviewed-by: Dave 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: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Yu-cheng Yu 2016-07-11 09:18:57 -07:00 committed by Ingo Molnar
parent 35ac2d7ba7
commit b8be15d588
2 changed files with 9 additions and 15 deletions
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15
arch/x86/kernel/fpu/init.c
View File

@ -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);
}
/*

9
arch/x86/kernel/fpu/xstate.c
View File

@ -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);