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From: Nadav Amit <namit@vmware.com>
To: <linux-kernel@vger.kernel.org>, <x86@kernel.org>
Cc: Nadav Amit <namit@vmware.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
	Peter Zijlstra <peterz@infradead.org>
Subject: [PATCH v2 8/9] x86: cpufeature: use macros instead of inline assembly
Date: Mon, 4 Jun 2018 04:21:30 -0700	[thread overview]
Message-ID: <20180604112131.59100-9-namit@vmware.com> (raw)
In-Reply-To: <20180604112131.59100-1-namit@vmware.com>

Use assembly macros for static_cpu_has() and call them from inline
assembly.  This not only makes the code more readable, but also improves
compilation decision, specifically inline decisions which GCC base on
the number of new lines in inline assembly.

The patch slightly increases the kernel size:

   text	   data	    bss	    dec	    hex	filename
18162879 10226256 2957312 31346447 1de4f0f ./vmlinux before
18163528 10226300 2957312 31347140 1de51c4 ./vmlinux after (+693)

And enables the inlining of function such as free_ldt_pgtables().

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org
Cc: Peter Zijlstra <peterz@infradead.org>

Signed-off-by: Nadav Amit <namit@vmware.com>
---
 arch/x86/include/asm/cpufeature.h | 82 ++++++++++++++++++-------------
 arch/x86/kernel/macros.S          |  1 +
 2 files changed, 48 insertions(+), 35 deletions(-)

diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h
index b27da9602a6d..33e45dfb211a 100644
--- a/arch/x86/include/asm/cpufeature.h
+++ b/arch/x86/include/asm/cpufeature.h
@@ -2,10 +2,10 @@
 #ifndef _ASM_X86_CPUFEATURE_H
 #define _ASM_X86_CPUFEATURE_H
 
-#include <asm/processor.h>
-
-#if defined(__KERNEL__) && !defined(__ASSEMBLY__)
+#ifdef __KERNEL__
+#ifndef __ASSEMBLY__
 
+#include <asm/processor.h>
 #include <asm/asm.h>
 #include <linux/bitops.h>
 
@@ -147,37 +147,10 @@ extern void clear_cpu_cap(struct cpuinfo_x86 *c, unsigned int bit);
  */
 static __always_inline __pure bool _static_cpu_has(u16 bit)
 {
-	asm_volatile_goto("1: jmp 6f\n"
-		 "2:\n"
-		 ".skip -(((5f-4f) - (2b-1b)) > 0) * "
-			 "((5f-4f) - (2b-1b)),0x90\n"
-		 "3:\n"
-		 ".section .altinstructions,\"a\"\n"
-		 " .long 1b - .\n"		/* src offset */
-		 " .long 4f - .\n"		/* repl offset */
-		 " .word %P[always]\n"		/* always replace */
-		 " .byte 3b - 1b\n"		/* src len */
-		 " .byte 5f - 4f\n"		/* repl len */
-		 " .byte 3b - 2b\n"		/* pad len */
-		 ".previous\n"
-		 ".section .altinstr_replacement,\"ax\"\n"
-		 "4: jmp %l[t_no]\n"
-		 "5:\n"
-		 ".previous\n"
-		 ".section .altinstructions,\"a\"\n"
-		 " .long 1b - .\n"		/* src offset */
-		 " .long 0\n"			/* no replacement */
-		 " .word %P[feature]\n"		/* feature bit */
-		 " .byte 3b - 1b\n"		/* src len */
-		 " .byte 0\n"			/* repl len */
-		 " .byte 0\n"			/* pad len */
-		 ".previous\n"
-		 ".section .altinstr_aux,\"ax\"\n"
-		 "6:\n"
-		 " testb %[bitnum],%[cap_byte]\n"
-		 " jnz %l[t_yes]\n"
-		 " jmp %l[t_no]\n"
-		 ".previous\n"
+	asm_volatile_goto("STATIC_CPU_HAS bitnum=%[bitnum] "
+			  "cap_byte=\"%[cap_byte]\" "
+			  "feature=%P[feature] t_yes=%l[t_yes] "
+			  "t_no=%l[t_no] always=%P[always]"
 		 : : [feature]  "i" (bit),
 		     [always]   "i" (X86_FEATURE_ALWAYS),
 		     [bitnum]   "i" (1 << (bit & 7)),
@@ -211,5 +184,44 @@ static __always_inline __pure bool _static_cpu_has(u16 bit)
 #define CPU_FEATURE_TYPEVAL		boot_cpu_data.x86_vendor, boot_cpu_data.x86, \
 					boot_cpu_data.x86_model
 
-#endif /* defined(__KERNEL__) && !defined(__ASSEMBLY__) */
+#else /* __ASSEMBLY__ */
+
+.macro STATIC_CPU_HAS bitnum:req cap_byte:req feature:req t_yes:req t_no:req always:req
+1:
+	jmp 6f
+2:
+	.skip -(((5f-4f) - (2b-1b)) > 0) * ((5f-4f) - (2b-1b)),0x90
+3:
+	.section .altinstructions,"a"
+	.long 1b - .		/* src offset */
+	.long 4f - .		/* repl offset */
+	.word \always		/* always replace */
+	.byte 3b - 1b		/* src len */
+	.byte 5f - 4f		/* repl len */
+	.byte 3b - 2b		/* pad len */
+	.previous
+	.section .altinstr_replacement,"ax"
+4:
+	jmp \t_no
+5:
+	.previous
+	.section .altinstructions,"a"
+	.long 1b - .		/* src offset */
+	.long 0			/* no replacement */
+	.word \feature		/* feature bit */
+	.byte 3b - 1b		/* src len */
+	.byte 0			/* repl len */
+	.byte 0			/* pad len */
+	.previous
+	.section .altinstr_aux,"ax"
+6:
+	testb \bitnum,\cap_byte
+	jnz \t_yes
+	jmp \t_no
+	.previous
+.endm
+
+#endif /* __ASSEMBLY__ */
+
+#endif /* __KERNEL__ */
 #endif /* _ASM_X86_CPUFEATURE_H */
diff --git a/arch/x86/kernel/macros.S b/arch/x86/kernel/macros.S
index 7baa40d5bf16..bf8b9c93e255 100644
--- a/arch/x86/kernel/macros.S
+++ b/arch/x86/kernel/macros.S
@@ -12,3 +12,4 @@
 #include <asm/bug.h>
 #include <asm/paravirt.h>
 #include <asm/asm.h>
+#include <asm/cpufeature.h>
-- 
2.17.0

  parent reply	other threads:[~2018-06-04 18:37 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-06-04 11:21 [PATCH v2 0/9] x86: macrofying inline asm for better compilation Nadav Amit
2018-06-04 11:21 ` [PATCH v2 1/9] Makefile: Prepare for using macros for inline asm Nadav Amit
2018-06-04 11:21 ` [PATCH v2 2/9] x86: objtool: use asm macro for better compiler decisions Nadav Amit
2018-06-04 19:04   ` Josh Poimboeuf
2018-06-05  5:41   ` kbuild test robot
2018-06-04 11:21 ` [PATCH v2 3/9] x86: refcount: prevent gcc distortions Nadav Amit
2018-06-04 22:06   ` Kees Cook
2018-06-04 22:20     ` Nadav Amit
2018-06-05  8:26   ` kbuild test robot
2018-06-04 11:21 ` [PATCH v2 4/9] x86: alternatives: macrofy locks for better inlining Nadav Amit
2018-06-05  5:36   ` kbuild test robot
2018-06-05 14:07   ` kbuild test robot
2018-06-07  3:05   ` [lkp-robot] [x86] 1a39381d70: WARNING:at_kernel/locking/mutex.c:#__mutex_unlock_slowpath kernel test robot
2018-06-04 11:21 ` [PATCH v2 5/9] x86: bug: prevent gcc distortions Nadav Amit
2018-06-05  7:34   ` kbuild test robot
2018-06-04 11:21 ` [PATCH v2 6/9] x86: prevent inline distortion by paravirt ops Nadav Amit
2018-06-04 11:21 ` [PATCH v2 7/9] x86: extable: use macros instead of inline assembly Nadav Amit
2018-06-04 11:21 ` Nadav Amit [this message]
2018-06-04 11:21 ` [PATCH v2 9/9] x86: jump-labels: " Nadav Amit
2018-06-04 19:05 ` [PATCH v2 0/9] x86: macrofying inline asm for better compilation Josh Poimboeuf
2018-06-04 19:56   ` Nadav Amit

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