x86: add NOPL as a synthetic CPU feature bit

The long noops ("NOPL") are supposed to be detected by family >= 6.
Unfortunately, several non-Intel x86 implementations, both hardware
and software, don't obey this dictum.  Instead, probe for NOPL
directly by executing a NOPL instruction and see if we get #UD.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>

2 files changed, 13 insertions, 6 deletions

diff --git a/include/asm-x86/cpufeature.h b/include/asm-x86/cpufeature.h
index 762f6a6bc707..9489283a4bcf 100644
--- a/include/asm-x86/cpufeature.h
+++ b/include/asm-x86/cpufeature.h
@@ -72,14 +72,15 @@
 #define X86_FEATURE_UP          (3*32+ 9) /* smp kernel running on up */
 #define X86_FEATURE_FXSAVE_LEAK (3*32+10) /* FXSAVE leaks FOP/FIP/FOP */
 #define X86_FEATURE_ARCH_PERFMON (3*32+11) /* Intel Architectural PerfMon */
-#define X86_FEATURE_PEBS        (3*32+12)  /* Precise-Event Based Sampling */
-#define X86_FEATURE_BTS         (3*32+13)  /* Branch Trace Store */
-#define X86_FEATURE_SYSCALL32   (3*32+14)  /* syscall in ia32 userspace */
-#define X86_FEATURE_SYSENTER32  (3*32+15)  /* sysenter in ia32 userspace */
+#define X86_FEATURE_PEBS        (3*32+12) /* Precise-Event Based Sampling */
+#define X86_FEATURE_BTS         (3*32+13) /* Branch Trace Store */
+#define X86_FEATURE_SYSCALL32   (3*32+14) /* syscall in ia32 userspace */
+#define X86_FEATURE_SYSENTER32  (3*32+15) /* sysenter in ia32 userspace */
 #define X86_FEATURE_REP_GOOD    (3*32+16) /* rep microcode works well on this CPU */
 #define X86_FEATURE_MFENCE_RDTSC (3*32+17) /* Mfence synchronizes RDTSC */
 #define X86_FEATURE_LFENCE_RDTSC (3*32+18) /* Lfence synchronizes RDTSC */
-#define X86_FEATURE_11AP        (3*32+19)  /* Bad local APIC aka 11AP */
+#define X86_FEATURE_11AP        (3*32+19) /* Bad local APIC aka 11AP */
+#define X86_FEATURE_NOPL        (3*32+20) /* The NOPL (0F 1F) instructions */
 
 /* Intel-defined CPU features, CPUID level 0x00000001 (ecx), word 4 */
 #define X86_FEATURE_XMM3        (4*32+ 0) /* Streaming SIMD Extensions-3 */
diff --git a/include/asm-x86/required-features.h b/include/asm-x86/required-features.h
index adec887dd7cd..5c2ff4bc2980 100644
--- a/include/asm-x86/required-features.h
+++ b/include/asm-x86/required-features.h
@@ -41,6 +41,12 @@
 # define NEED_3DNOW     0
 #endif
 
+#if defined(CONFIG_X86_P6_NOP) || defined(CONFIG_X86_64)
+# define NEED_NOPL      (1<<(X86_FEATURE_NOPL & 31))
+#else
+# define NEED_NOPL      0
+#endif
+
 #ifdef CONFIG_X86_64
 #define NEED_PSE        0
 #define NEED_MSR        (1<<(X86_FEATURE_MSR & 31))
@@ -67,7 +73,7 @@
 #define REQUIRED_MASK1  (NEED_LM|NEED_3DNOW)
 
 #define REQUIRED_MASK2  0
-#define REQUIRED_MASK3  0
+#define REQUIRED_MASK3  (NEED_NOPL)
 #define REQUIRED_MASK4  0
 #define REQUIRED_MASK5  0
 #define REQUIRED_MASK6  0