x86/fpu/xstate: Re-enable XSAVES (b8be15d5) · Commits · 戴 / test

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>

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);

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