Commit 4797e9b5 authored by Heiko Carstens's avatar Heiko Carstens Committed by Vasily Gorbik
Browse files

s390/smp: Implement raw_smp_processor_id() with inline assembly 



Implement raw_smp_processor_id() with an inline assembly, which makes
use of the ALTERNATIVE macro, to read cpu_nr from lowcore. Provide an
alternative instruction with a different offset in case lowcore is
relocated.

This replaces sequences of two instructions with one instruction.

Before:
  1000b6:       a5 1e 00 00             llilh   %r1,0
  1000ba:       58 20 13 a0             l       %r2,928(%r1)

After:
  1000b6:       e3 20 03 a0 00 58       ly      %r2,928

Kernel image size change:
add/remove: 753/755 grow/shrink: 230/1510 up/down: 30538/-35832 (-5294)

Acked-by: default avatarVasily Gorbik <gor@linux.ibm.com>
Signed-off-by: default avatarHeiko Carstens <hca@linux.ibm.com>
Signed-off-by: default avatarVasily Gorbik <gor@linux.ibm.com>
parent 65c07e91

arch/s390/include/asm/smp.h

+21 −3
Original line number Diff line number Diff line
@@ -7,11 +7,29 @@ 
#ifndef __ASM_SMP_H

#define __ASM_SMP_H



#include <asm/sigp.h>

#include <asm/lowcore.h>

#include <asm/processor.h>

#include <asm/lowcore.h>

#include <asm/machine.h>

#include <asm/sigp.h>



static __always_inline unsigned int raw_smp_processor_id(void)

{

	unsigned long lc_cpu_nr;

	unsigned int cpu;



	BUILD_BUG_ON(sizeof_field(struct lowcore, cpu_nr) != sizeof(cpu));

	lc_cpu_nr = offsetof(struct lowcore, cpu_nr);

	asm_inline(

		ALTERNATIVE("   ly      %[cpu],%[offzero](%%r0)\n",

			    "   ly      %[cpu],%[offalt](%%r0)\n",

			    ALT_FEATURE(MFEATURE_LOWCORE))

		: [cpu] "=d" (cpu)

		: [offzero] "i" (lc_cpu_nr),

		  [offalt] "i" (lc_cpu_nr + LOWCORE_ALT_ADDRESS),

		  "m" (((struct lowcore *)0)->cpu_nr));

	return cpu;

}



#define raw_smp_processor_id()	(get_lowcore()->cpu_nr)

#define arch_scale_cpu_capacity smp_cpu_get_capacity



extern struct mutex smp_cpu_state_mutex;