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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: 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>
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@ -230,21 +230,6 @@ static void __init fpu__init_system_xstate_size_legacy(void)
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}
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fpu_user_xstate_size = fpu_kernel_xstate_size;
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/*
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* Quirk: we don't yet handle the XSAVES* instructions
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* correctly, as we don't correctly convert between
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* standard and compacted format when interfacing
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* with user-space - so disable it for now.
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*
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* The difference is small: with recent CPUs the
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* compacted format is only marginally smaller than
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* the standard FPU state format.
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*
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* ( This is easy to backport while we are fixing
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* XSAVES* support. )
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*/
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setup_clear_cpu_cap(X86_FEATURE_XSAVES);
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}
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/*
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@ -221,6 +221,15 @@ void fpu__init_cpu_xstate(void)
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{
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if (!boot_cpu_has(X86_FEATURE_XSAVE) || !xfeatures_mask)
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return;
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/*
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* Make it clear that XSAVES supervisor states are not yet
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* implemented should anyone expect it to work by changing
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* bits in XFEATURE_MASK_* macros and XCR0.
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*/
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WARN_ONCE((xfeatures_mask & XFEATURE_MASK_SUPERVISOR),
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"x86/fpu: XSAVES supervisor states are not yet implemented.\n");
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xfeatures_mask &= ~XFEATURE_MASK_SUPERVISOR;
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cr4_set_bits(X86_CR4_OSXSAVE);
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xsetbv(XCR_XFEATURE_ENABLED_MASK, xfeatures_mask);
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