linux-kernel - [PATCH 2/3] x86, cpufeatures: make sure DISABLED/REQUIRED macros are updated

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Date:	Wed, 29 Jun 2016 13:01:08 -0700
From:	Dave Hansen <dave@...1.net>
To:	linux-kernel@...r.kernel.org
Cc:	x86@...nel.org, Dave Hansen <dave@...1.net>,
	dave.hansen@...ux.intel.com
Subject: [PATCH 2/3] x86, cpufeatures: make sure DISABLED/REQUIRED macros are updated


From: Dave Hansen <dave.hansen@...ux.intel.com>

x86 has two macros which allow us to evaluate some CPUID-based
features at compile time:

	REQUIRED_MASK_BIT_SET()
	DISABLED_MASK_BIT_SET()

They're both defined by having the compiler check the bit
argument against some constant masks of features.

But, when adding new CPUID leaves, we need to check new words
for these macros.  So make sure that those macros and the
REQUIRED_MASK* and DISABLED_MASK* get updated when necessary.

This looks kinda silly to have an open-coded value ("18" in
this case) open-coded in 5 places in the code.  But, we really do
need 5 places updated when NCAPINTS gets bumped, so now we just
force the issue.

Signed-off-by: Dave Hansen <dave.hansen@...ux.intel.com>
---

 b/arch/x86/include/asm/cpufeature.h        |    8 ++++++--
 b/arch/x86/include/asm/disabled-features.h |    1 +
 b/arch/x86/include/asm/required-features.h |    1 +
 3 files changed, 8 insertions(+), 2 deletions(-)

diff -puN arch/x86/include/asm/cpufeature.h~x86-make-sure-macros-are-updated arch/x86/include/asm/cpufeature.h
--- a/arch/x86/include/asm/cpufeature.h~x86-make-sure-macros-are-updated	2016-06-29 12:59:58.212523211 -0700
+++ b/arch/x86/include/asm/cpufeature.h	2016-06-29 12:59:58.219523528 -0700
@@ -67,7 +67,9 @@ extern const char * const x86_bug_flags[
 	   (((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)))
+	   (((bit)>>5)==17 && (1UL<<((bit)&31) & REQUIRED_MASK17)) ||	\
+	   REQUIRED_MASK_CHECK					   ||	\
+	   BUILD_BUG_ON_ZERO(NCAPINTS != 18))
 
 #define DISABLED_MASK_BIT_SET(bit)					\
 	 ( (((bit)>>5)==0  && (1UL<<((bit)&31) & DISABLED_MASK0 )) ||	\
@@ -87,7 +89,9 @@ extern const char * const x86_bug_flags[
 	   (((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)))
+	   (((bit)>>5)==17 && (1UL<<((bit)&31) & DISABLED_MASK17)) ||	\
+	   DISABLED_MASK_CHECK					   ||	\
+	   BUILD_BUG_ON_ZERO(NCAPINTS != 18))
 
 #define cpu_has(c, bit)							\
 	(__builtin_constant_p(bit) && REQUIRED_MASK_BIT_SET(bit) ? 1 :	\
diff -puN arch/x86/include/asm/disabled-features.h~x86-make-sure-macros-are-updated arch/x86/include/asm/disabled-features.h
--- a/arch/x86/include/asm/disabled-features.h~x86-make-sure-macros-are-updated	2016-06-29 12:59:58.214523302 -0700
+++ b/arch/x86/include/asm/disabled-features.h	2016-06-29 12:59:58.219523528 -0700
@@ -57,5 +57,6 @@
 #define DISABLED_MASK15	0
 #define DISABLED_MASK16	(DISABLE_PKU|DISABLE_OSPKE)
 #define DISABLED_MASK17	0
+#define DISABLED_MASK_CHECK BUILD_BUG_ON_ZERO(NCAPINTS != 18)
 
 #endif /* _ASM_X86_DISABLED_FEATURES_H */
diff -puN arch/x86/include/asm/required-features.h~x86-make-sure-macros-are-updated arch/x86/include/asm/required-features.h
--- a/arch/x86/include/asm/required-features.h~x86-make-sure-macros-are-updated	2016-06-29 12:59:58.215523347 -0700
+++ b/arch/x86/include/asm/required-features.h	2016-06-29 12:59:58.219523528 -0700
@@ -100,5 +100,6 @@
 #define REQUIRED_MASK15	0
 #define REQUIRED_MASK16	0
 #define REQUIRED_MASK17	0
+#define REQUIRED_MASK_CHECK BUILD_BUG_ON_ZERO(NCAPINTS != 18)
 
 #endif /* _ASM_X86_REQUIRED_FEATURES_H */
_