aboutsummaryrefslogtreecommitdiff
diff options
context:
space:
mode:
authorYu-cheng Yu <yu-cheng.yu@intel.com>2016-03-09 16:28:54 -0800
committerIngo Molnar <mingo@kernel.org>2016-03-10 10:15:58 +0100
commita65050c6f17e52442716138d48d0a47301a8344b (patch)
tree9e7ddf9c8213d2dc7cc74bb0fa75b058fd0b483c
parentf363938c70a04e6bc99023a5e0c44ef7879b903f (diff)
downloadlinux-stericsson-a65050c6f17e52442716138d48d0a47301a8344b.tar.gz
x86/fpu: Revert ("x86/fpu: Disable AVX when eagerfpu is off")
Leonid Shatz noticed that the SDM interpretation of the following recent commit: 394db20ca240741 ("x86/fpu: Disable AVX when eagerfpu is off") ... is incorrect and that the original behavior of the FPU code was correct. Because AVX is not stated in CR0 TS bit description, it was mistakenly believed to be not supported for lazy context switch. This turns out to be false: Intel Software Developer's Manual Vol. 3A, Sec. 2.5 Control Registers: 'TS Task Switched bit (bit 3 of CR0) -- Allows the saving of the x87 FPU/ MMX/SSE/SSE2/SSE3/SSSE3/SSE4 context on a task switch to be delayed until an x87 FPU/MMX/SSE/SSE2/SSE3/SSSE3/SSE4 instruction is actually executed by the new task.' Intel Software Developer's Manual Vol. 2A, Sec. 2.4 Instruction Exception Specification: 'AVX instructions refer to exceptions by classes that include #NM "Device Not Available" exception for lazy context switch.' So revert the commit. Reported-by: Leonid Shatz <leonid.shatz@ravellosystems.com> Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Borislav Petkov <bp@suse.de> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Fenghua Yu <fenghua.yu@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: Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/1457569734-3785-1-git-send-email-yu-cheng.yu@intel.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
-rw-r--r--arch/x86/include/asm/fpu/xstate.h9
-rw-r--r--arch/x86/kernel/fpu/init.c6
2 files changed, 4 insertions, 11 deletions
diff --git a/arch/x86/include/asm/fpu/xstate.h b/arch/x86/include/asm/fpu/xstate.h
index af30fdeb140d..f23cd8c80b1c 100644
--- a/arch/x86/include/asm/fpu/xstate.h
+++ b/arch/x86/include/asm/fpu/xstate.h
@@ -20,16 +20,15 @@
/* Supported features which support lazy state saving */
#define XFEATURE_MASK_LAZY (XFEATURE_MASK_FP | \
- XFEATURE_MASK_SSE)
-
-/* Supported features which require eager state saving */
-#define XFEATURE_MASK_EAGER (XFEATURE_MASK_BNDREGS | \
- XFEATURE_MASK_BNDCSR | \
+ XFEATURE_MASK_SSE | \
XFEATURE_MASK_YMM | \
XFEATURE_MASK_OPMASK | \
XFEATURE_MASK_ZMM_Hi256 | \
XFEATURE_MASK_Hi16_ZMM)
+/* Supported features which require eager state saving */
+#define XFEATURE_MASK_EAGER (XFEATURE_MASK_BNDREGS | XFEATURE_MASK_BNDCSR)
+
/* All currently supported features */
#define XCNTXT_MASK (XFEATURE_MASK_LAZY | XFEATURE_MASK_EAGER)
diff --git a/arch/x86/kernel/fpu/init.c b/arch/x86/kernel/fpu/init.c
index d53ab3d3b8e8..9ee7e307b18f 100644
--- a/arch/x86/kernel/fpu/init.c
+++ b/arch/x86/kernel/fpu/init.c
@@ -302,12 +302,6 @@ u64 __init fpu__get_supported_xfeatures_mask(void)
static void __init fpu__clear_eager_fpu_features(void)
{
setup_clear_cpu_cap(X86_FEATURE_MPX);
- setup_clear_cpu_cap(X86_FEATURE_AVX);
- setup_clear_cpu_cap(X86_FEATURE_AVX2);
- setup_clear_cpu_cap(X86_FEATURE_AVX512F);
- setup_clear_cpu_cap(X86_FEATURE_AVX512PF);
- setup_clear_cpu_cap(X86_FEATURE_AVX512ER);
- setup_clear_cpu_cap(X86_FEATURE_AVX512CD);
}
/*