From f685a96bfd7963a587c76bd5709f2d9170820875 Mon Sep 17 00:00:00 2001 From: Uros Bizjak Date: Thu, 13 Mar 2025 11:26:56 +0100 Subject: [PATCH] x86/asm: Use asm_inline() instead of asm() in clwb() Use asm_inline() to instruct the compiler that the size of asm() is the minimum size of one instruction, ignoring how many instructions the compiler thinks it is. ALTERNATIVE macro that expands to several pseudo directives causes instruction length estimate to count more than 20 instructions. bloat-o-meter reports slight increase of the code size for x86_64 defconfig object file, compiled with gcc-14.2: add/remove: 0/2 grow/shrink: 3/0 up/down: 190/-59 (131) Function old new delta __copy_user_flushcache 166 247 +81 __memcpy_flushcache 369 437 +68 arch_wb_cache_pmem 6 47 +41 __pfx_clean_cache_range 16 - -16 clean_cache_range 43 - -43 Total: Before=22807167, After=22807298, chg +0.00% The compiler now inlines and removes the clean_cache_range() function. Signed-off-by: Uros Bizjak Signed-off-by: Ingo Molnar Cc: Andy Lutomirski Cc: Brian Gerst Cc: H. Peter Anvin Cc: Linus Torvalds Link: https://lore.kernel.org/r/20250313102715.333142-2-ubizjak@gmail.com --- arch/x86/include/asm/special_insns.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/include/asm/special_insns.h b/arch/x86/include/asm/special_insns.h index 9b10bd102d3d..6266d6b9e0b8 100644 --- a/arch/x86/include/asm/special_insns.h +++ b/arch/x86/include/asm/special_insns.h @@ -185,7 +185,7 @@ static inline void clwb(volatile void *__p) { volatile struct { char x[64]; } *p = __p; - asm volatile(ALTERNATIVE_2( + asm_inline volatile(ALTERNATIVE_2( "ds clflush %0", "clflushopt %0", X86_FEATURE_CLFLUSHOPT, "clwb %0", X86_FEATURE_CLWB)