x86/fpu: Disable XGETBV1 when no XSAVE

yyu-intel-com · Ingo Molnar · commit eb7c5f872e69 · 2016-01-12T11:51:21.000+01:00
When "noxsave" is given as a command-line input, the kernel should disable XGETBV1. This issue currently does not cause any actual problems. XGETBV1 is only useful if we have something using the 'init optimization' (i.e. xsaveopt, xsaves). We already clear both of those in fpu__xstate_clear_all_cpu_caps(). But this is good for completeness. Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com> Reviewed-by: Dave Hansen <dave.hansen@intel.com> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Borislav Petkov <bp@alien8.de> Cc: Borislav Petkov <bp@suse.de> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Fenghua Yu <fenghua.yu@intel.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Quentin Casasnovas <quentin.casasnovas@oracle.com> Cc: Ravi V. Shankar <ravi.v.shankar@intel.com> Cc: Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: yu-cheng yu <yu-cheng.yu@intel.com> Link: http://lkml.kernel.org/r/1452119094-7252-3-git-send-email-yu-cheng.yu@intel.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
@@ -52,6 +52,7 @@ void fpu__xstate_clear_all_cpu_caps(void)
 	setup_clear_cpu_cap(X86_FEATURE_AVX512ER);
 	setup_clear_cpu_cap(X86_FEATURE_AVX512CD);
 	setup_clear_cpu_cap(X86_FEATURE_MPX);
+	setup_clear_cpu_cap(X86_FEATURE_XGETBV1);
 }
 
 /*

Original file line number	Diff line number	Diff line change
`@@ -52,6 +52,7 @@ void fpu__xstate_clear_all_cpu_caps(void)`
`52`	`52`	`setup_clear_cpu_cap(X86_FEATURE_AVX512ER);`
`53`	`53`	`setup_clear_cpu_cap(X86_FEATURE_AVX512CD);`
`54`	`54`	`setup_clear_cpu_cap(X86_FEATURE_MPX);`
	`55`	`+ setup_clear_cpu_cap(X86_FEATURE_XGETBV1);`
`55`	`56`	`}`
`56`	`57`
`57`	`58`	`/*`