x86/asm: Cleanup prefetch primitives

This is based on a patch originally by hpa.

With the current improvements to the alternatives, we can simply use %P1
as a mem8 operand constraint and rely on the toolchain to generate the
proper instruction sizes. For example, on 32-bit, where we use an empty
old instruction we get:

  apply_alternatives: feat: 6*32+8, old: (c104648b, len: 4), repl: (c195566c, len: 4)
  c104648b: alt_insn: 90 90 90 90
  c195566c: rpl_insn: 0f 0d 4b 5c

  ...

  apply_alternatives: feat: 6*32+8, old: (c18e09b4, len: 3), repl: (c1955948, len: 3)
  c18e09b4: alt_insn: 90 90 90
  c1955948: rpl_insn: 0f 0d 08

  ...

  apply_alternatives: feat: 6*32+8, old: (c1190cf9, len: 7), repl: (c1955a79, len: 7)
  c1190cf9: alt_insn: 90 90 90 90 90 90 90
  c1955a79: rpl_insn: 0f 0d 0d a0 d4 85 c1

all with the proper padding done depending on the size of the
replacement instruction the compiler generates.

Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: H. Peter Anvin <hpa@linux.intel.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h
index efc3b22d896e..8118e94d50ab 100644
--- a/arch/x86/include/asm/apic.h
+++ b/arch/x86/include/asm/apic.h
@@ -91,7 +91,7 @@ static inline void native_apic_mem_write(u32 reg, u32 v)
 {
 	volatile u32 *addr = (volatile u32 *)(APIC_BASE + reg);
 
-	alternative_io("movl %0, %1", "xchgl %0, %1", X86_BUG_11AP,
+	alternative_io("movl %0, %P1", "xchgl %0, %P1", X86_BUG_11AP,
 		       ASM_OUTPUT2("=r" (v), "=m" (*addr)),
 		       ASM_OUTPUT2("0" (v), "m" (*addr)));
 }