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>

1 files changed, 7 insertions, 1 deletions

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