From: Heiko Carstens Date: Mon, 10 Mar 2025 09:33:40 +0000 (+0100) Subject: s390/smp: Implement raw_smp_processor_id() with inline assembly X-Git-Tag: v6.15-rc1~113^2~10 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=4797e9b5067e3682020b3f6745a929d690370be3;p=thirdparty%2Fkernel%2Flinux.git 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: Vasily Gorbik Signed-off-by: Heiko Carstens Signed-off-by: Vasily Gorbik --- diff --git a/arch/s390/include/asm/smp.h b/arch/s390/include/asm/smp.h index 7feca96c48c6a..03f4d01664f8a 100644 --- a/arch/s390/include/asm/smp.h +++ b/arch/s390/include/asm/smp.h @@ -7,11 +7,29 @@ #ifndef __ASM_SMP_H #define __ASM_SMP_H -#include -#include #include +#include +#include +#include + +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;