linux-kernel - [PATCH v2 5/6] x86: alternative.h: use asm

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Date:   Sat, 31 Aug 2019 01:15:26 +0200
From:   Rasmus Villemoes <linux@...musvillemoes.dk>
To:     x86@...nel.org, linux-kernel@...r.kernel.org
Cc:     Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>, Nadav Amit <namit@...are.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Miguel Ojeda <miguel.ojeda.sandonis@...il.com>,
        ndesaulniers@...gle.com,
        Rasmus Villemoes <linux@...musvillemoes.dk>
Subject: [PATCH v2 5/6] x86: alternative.h: use asm_inline for all alternative variants

Most, if not all, uses of the alternative* family just provide one or
two instructions in .text, but the string literal can be quite large,
causing gcc to overestimate the size of the generated code. That in
turn affects its decisions about inlining of the function containing
the alternative() asm statement.

gcc >= 9.1 allows one to overrule the estimated size by using "asm
inline" instead of just "asm". So replace asm by the helper
asm_inline, which for older gccs just expands to asm.

Signed-off-by: Rasmus Villemoes <linux@...musvillemoes.dk>
---
 arch/x86/include/asm/alternative.h | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h
index 094fbc9c0b1c..13adca37c99a 100644
--- a/arch/x86/include/asm/alternative.h
+++ b/arch/x86/include/asm/alternative.h
@@ -201,10 +201,10 @@ static inline int alternatives_text_reserved(void *start, void *end)
  * without volatile and memory clobber.
  */
 #define alternative(oldinstr, newinstr, feature)			\
-	asm volatile (ALTERNATIVE(oldinstr, newinstr, feature) : : : "memory")
+	asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, feature) : : : "memory")
 
 #define alternative_2(oldinstr, newinstr1, feature1, newinstr2, feature2) \
-	asm volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2) ::: "memory")
+	asm_inline volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2) ::: "memory")
 
 /*
  * Alternative inline assembly with input.
@@ -218,7 +218,7 @@ static inline int alternatives_text_reserved(void *start, void *end)
  * Leaving an unused argument 0 to keep API compatibility.
  */
 #define alternative_input(oldinstr, newinstr, feature, input...)	\
-	asm volatile (ALTERNATIVE(oldinstr, newinstr, feature)		\
+	asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, feature)	\
 		: : "i" (0), ## input)
 
 /*
@@ -231,18 +231,18 @@ static inline int alternatives_text_reserved(void *start, void *end)
  */
 #define alternative_input_2(oldinstr, newinstr1, feature1, newinstr2,	     \
 			   feature2, input...)				     \
-	asm volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1,	     \
+	asm_inline volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1,     \
 		newinstr2, feature2)					     \
 		: : "i" (0), ## input)
 
 /* Like alternative_input, but with a single output argument */
 #define alternative_io(oldinstr, newinstr, feature, output, input...)	\
-	asm volatile (ALTERNATIVE(oldinstr, newinstr, feature)		\
+	asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, feature)	\
 		: output : "i" (0), ## input)
 
 /* Like alternative_io, but for replacing a direct call with another one. */
 #define alternative_call(oldfunc, newfunc, feature, output, input...)	\
-	asm volatile (ALTERNATIVE("call %P[old]", "call %P[new]", feature) \
+	asm_inline volatile (ALTERNATIVE("call %P[old]", "call %P[new]", feature) \
 		: output : [old] "i" (oldfunc), [new] "i" (newfunc), ## input)
 
 /*
@@ -253,7 +253,7 @@ static inline int alternatives_text_reserved(void *start, void *end)
  */
 #define alternative_call_2(oldfunc, newfunc1, feature1, newfunc2, feature2,   \
 			   output, input...)				      \
-	asm volatile (ALTERNATIVE_2("call %P[old]", "call %P[new1]", feature1,\
+	asm_inline volatile (ALTERNATIVE_2("call %P[old]", "call %P[new1]", feature1,\
 		"call %P[new2]", feature2)				      \
 		: output, ASM_CALL_CONSTRAINT				      \
 		: [old] "i" (oldfunc), [new1] "i" (newfunc1),		      \
-- 
2.20.1