x86/cpufeature: Add helper macro for mask check macros

Every time we add a word to our cpu features, we need to add
something like this in two places:

	(((bit)>>5)==16 && (1UL<<((bit)&31) & REQUIRED_MASK16))

The trick is getting the "16" in this case in both places.  I've
now screwed this up twice, so as pennance, I've come up with
this patch to keep me and other poor souls from doing the same.

I also commented the logic behind the bit manipulation showcased
above.

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave@sr71.net>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20160629200110.1BA8949E@viggo.jf.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h
index 7b20720..1d2b69f 100644 (file)
--- a/arch/x86/include/asm/cpufeature.h
+++ b/arch/x86/include/asm/cpufeature.h
@@ -49,48 +49,58 @@ extern const char * const x86_bug_flags[NBUGINTS*32];
 #define test_cpu_cap(c, bit)                                           \
         test_bit(bit, (unsigned long *)((c)->x86_capability))
 
-#define REQUIRED_MASK_BIT_SET(bit)                                     \
-        ( (((bit)>>5)==0  && (1UL<<((bit)&31) & REQUIRED_MASK0 )) ||   \
-          (((bit)>>5)==1  && (1UL<<((bit)&31) & REQUIRED_MASK1 )) ||   \
-          (((bit)>>5)==2  && (1UL<<((bit)&31) & REQUIRED_MASK2 )) ||   \
-          (((bit)>>5)==3  && (1UL<<((bit)&31) & REQUIRED_MASK3 )) ||   \
-          (((bit)>>5)==4  && (1UL<<((bit)&31) & REQUIRED_MASK4 )) ||   \
-          (((bit)>>5)==5  && (1UL<<((bit)&31) & REQUIRED_MASK5 )) ||   \
-          (((bit)>>5)==6  && (1UL<<((bit)&31) & REQUIRED_MASK6 )) ||   \
-          (((bit)>>5)==7  && (1UL<<((bit)&31) & REQUIRED_MASK7 )) ||   \
-          (((bit)>>5)==8  && (1UL<<((bit)&31) & REQUIRED_MASK8 )) ||   \
-          (((bit)>>5)==9  && (1UL<<((bit)&31) & REQUIRED_MASK9 )) ||   \
-          (((bit)>>5)==10 && (1UL<<((bit)&31) & REQUIRED_MASK10)) ||   \
-          (((bit)>>5)==11 && (1UL<<((bit)&31) & REQUIRED_MASK11)) ||   \
-          (((bit)>>5)==12 && (1UL<<((bit)&31) & REQUIRED_MASK12)) ||   \
-          (((bit)>>5)==13 && (1UL<<((bit)&31) & REQUIRED_MASK13)) ||   \
-          (((bit)>>5)==14 && (1UL<<((bit)&31) & REQUIRED_MASK14)) ||   \
-          (((bit)>>5)==15 && (1UL<<((bit)&31) & REQUIRED_MASK15)) ||   \
-          (((bit)>>5)==16 && (1UL<<((bit)&31) & REQUIRED_MASK16)) ||   \
-          (((bit)>>5)==17 && (1UL<<((bit)&31) & REQUIRED_MASK17)) ||   \
-          REQUIRED_MASK_CHECK                                     ||   \
+/*
+ * There are 32 bits/features in each mask word.  The high bits
+ * (selected with (bit>>5) give us the word number and the low 5
+ * bits give us the bit/feature number inside the word.
+ * (1UL<<((bit)&31) gives us a mask for the feature_bit so we can
+ * see if it is set in the mask word.
+ */
+#define CHECK_BIT_IN_MASK_WORD(maskname, word, bit)    \
+       (((bit)>>5)==(word) && (1UL<<((bit)&31) & maskname##word ))
+
+#define REQUIRED_MASK_BIT_SET(feature_bit)             \
+        ( CHECK_BIT_IN_MASK_WORD(REQUIRED_MASK,  0, feature_bit) ||    \
+          CHECK_BIT_IN_MASK_WORD(REQUIRED_MASK,  1, feature_bit) ||    \
+          CHECK_BIT_IN_MASK_WORD(REQUIRED_MASK,  2, feature_bit) ||    \
+          CHECK_BIT_IN_MASK_WORD(REQUIRED_MASK,  3, feature_bit) ||    \
+          CHECK_BIT_IN_MASK_WORD(REQUIRED_MASK,  4, feature_bit) ||    \
+          CHECK_BIT_IN_MASK_WORD(REQUIRED_MASK,  5, feature_bit) ||    \
+          CHECK_BIT_IN_MASK_WORD(REQUIRED_MASK,  6, feature_bit) ||    \
+          CHECK_BIT_IN_MASK_WORD(REQUIRED_MASK,  7, feature_bit) ||    \
+          CHECK_BIT_IN_MASK_WORD(REQUIRED_MASK,  8, feature_bit) ||    \
+          CHECK_BIT_IN_MASK_WORD(REQUIRED_MASK,  9, feature_bit) ||    \
+          CHECK_BIT_IN_MASK_WORD(REQUIRED_MASK, 10, feature_bit) ||    \
+          CHECK_BIT_IN_MASK_WORD(REQUIRED_MASK, 11, feature_bit) ||    \
+          CHECK_BIT_IN_MASK_WORD(REQUIRED_MASK, 12, feature_bit) ||    \
+          CHECK_BIT_IN_MASK_WORD(REQUIRED_MASK, 13, feature_bit) ||    \
+          CHECK_BIT_IN_MASK_WORD(REQUIRED_MASK, 14, feature_bit) ||    \
+          CHECK_BIT_IN_MASK_WORD(REQUIRED_MASK, 15, feature_bit) ||    \
+          CHECK_BIT_IN_MASK_WORD(REQUIRED_MASK, 16, feature_bit) ||    \
+          CHECK_BIT_IN_MASK_WORD(REQUIRED_MASK, 17, feature_bit) ||    \
+          REQUIRED_MASK_CHECK                                    ||    \
           BUILD_BUG_ON_ZERO(NCAPINTS != 18))
 
-#define DISABLED_MASK_BIT_SET(bit)                                     \
-        ( (((bit)>>5)==0  && (1UL<<((bit)&31) & DISABLED_MASK0 )) ||   \
-          (((bit)>>5)==1  && (1UL<<((bit)&31) & DISABLED_MASK1 )) ||   \
-          (((bit)>>5)==2  && (1UL<<((bit)&31) & DISABLED_MASK2 )) ||   \
-          (((bit)>>5)==3  && (1UL<<((bit)&31) & DISABLED_MASK3 )) ||   \
-          (((bit)>>5)==4  && (1UL<<((bit)&31) & DISABLED_MASK4 )) ||   \
-          (((bit)>>5)==5  && (1UL<<((bit)&31) & DISABLED_MASK5 )) ||   \
-          (((bit)>>5)==6  && (1UL<<((bit)&31) & DISABLED_MASK6 )) ||   \
-          (((bit)>>5)==7  && (1UL<<((bit)&31) & DISABLED_MASK7 )) ||   \
-          (((bit)>>5)==8  && (1UL<<((bit)&31) & DISABLED_MASK8 )) ||   \
-          (((bit)>>5)==9  && (1UL<<((bit)&31) & DISABLED_MASK9 )) ||   \
-          (((bit)>>5)==10 && (1UL<<((bit)&31) & DISABLED_MASK10)) ||   \
-          (((bit)>>5)==11 && (1UL<<((bit)&31) & DISABLED_MASK11)) ||   \
-          (((bit)>>5)==12 && (1UL<<((bit)&31) & DISABLED_MASK12)) ||   \
-          (((bit)>>5)==13 && (1UL<<((bit)&31) & DISABLED_MASK13)) ||   \
-          (((bit)>>5)==14 && (1UL<<((bit)&31) & DISABLED_MASK14)) ||   \
-          (((bit)>>5)==15 && (1UL<<((bit)&31) & DISABLED_MASK15)) ||   \
-          (((bit)>>5)==16 && (1UL<<((bit)&31) & DISABLED_MASK16)) ||   \
-          (((bit)>>5)==17 && (1UL<<((bit)&31) & DISABLED_MASK17)) ||   \
-          DISABLED_MASK_CHECK                                     ||   \
+#define DISABLED_MASK_BIT_SET(feature_bit)                             \
+        ( CHECK_BIT_IN_MASK_WORD(DISABLED_MASK,  0, feature_bit) ||    \
+          CHECK_BIT_IN_MASK_WORD(DISABLED_MASK,  1, feature_bit) ||    \
+          CHECK_BIT_IN_MASK_WORD(DISABLED_MASK,  2, feature_bit) ||    \
+          CHECK_BIT_IN_MASK_WORD(DISABLED_MASK,  3, feature_bit) ||    \
+          CHECK_BIT_IN_MASK_WORD(DISABLED_MASK,  4, feature_bit) ||    \
+          CHECK_BIT_IN_MASK_WORD(DISABLED_MASK,  5, feature_bit) ||    \
+          CHECK_BIT_IN_MASK_WORD(DISABLED_MASK,  6, feature_bit) ||    \
+          CHECK_BIT_IN_MASK_WORD(DISABLED_MASK,  7, feature_bit) ||    \
+          CHECK_BIT_IN_MASK_WORD(DISABLED_MASK,  8, feature_bit) ||    \
+          CHECK_BIT_IN_MASK_WORD(DISABLED_MASK,  9, feature_bit) ||    \
+          CHECK_BIT_IN_MASK_WORD(DISABLED_MASK, 10, feature_bit) ||    \
+          CHECK_BIT_IN_MASK_WORD(DISABLED_MASK, 11, feature_bit) ||    \
+          CHECK_BIT_IN_MASK_WORD(DISABLED_MASK, 12, feature_bit) ||    \
+          CHECK_BIT_IN_MASK_WORD(DISABLED_MASK, 13, feature_bit) ||    \
+          CHECK_BIT_IN_MASK_WORD(DISABLED_MASK, 14, feature_bit) ||    \
+          CHECK_BIT_IN_MASK_WORD(DISABLED_MASK, 15, feature_bit) ||    \
+          CHECK_BIT_IN_MASK_WORD(DISABLED_MASK, 16, feature_bit) ||    \
+          CHECK_BIT_IN_MASK_WORD(DISABLED_MASK, 17, feature_bit) ||    \
+          DISABLED_MASK_CHECK                                    ||    \
           BUILD_BUG_ON_ZERO(NCAPINTS != 18))
 
 #define cpu_has(c, bit)                                                        \