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| author | Heiko Carstens <hca@linux.ibm.com> | 2026-03-17 22:54:28 +0300 |
|---|---|---|
| committer | Vasily Gorbik <gor@linux.ibm.com> | 2026-03-24 23:00:41 +0300 |
| commit | fa8be59ce23df05d3e1190ce4238f6f875d3868d (patch) | |
| tree | a1892fd141250193b0e5dd278ba7b9e177f1368b | |
| parent | 7bbf70131f937ee5871e22d159ed2fc66795722f (diff) | |
| download | linux-fa8be59ce23df05d3e1190ce4238f6f875d3868d.tar.xz | |
s390/percpu: Provide arch_raw_cpu_ptr()
Provide an s390 specific arch_raw_cpu_ptr() implementation which avoids the
detour over get_lowcore() to get the lowcore pointer. The inline assembly
is implemented with an alternative so that relocated lowcore (percpu offset
is at a different address) is handled correctly.
This turns code like this
102f78: a7 39 00 00 lghi %r3,0
102f7c: e3 20 33 b8 00 08 ag %r2,952(%r3)
which adds the percpu offset to register r2 into a single instruction
102f7c: e3 20 33 b8 00 08 ag %r2,952(%r0)
and also avoids the need of a base register, thus reducing register
pressure.
With defconfig bloat-o-meter -t provides this result:
add/remove: 12/26 grow/shrink: 183/3391 up/down: 14880/-41950 (-27070)
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
| -rw-r--r-- | arch/s390/include/asm/percpu.h | 18 |
1 files changed, 18 insertions, 0 deletions
diff --git a/arch/s390/include/asm/percpu.h b/arch/s390/include/asm/percpu.h index 5899f57f17d1..b18a96f3a334 100644 --- a/arch/s390/include/asm/percpu.h +++ b/arch/s390/include/asm/percpu.h @@ -12,6 +12,24 @@ */ #define __my_cpu_offset get_lowcore()->percpu_offset +#define arch_raw_cpu_ptr(_ptr) \ +({ \ + unsigned long lc_percpu, tcp_ptr__; \ + \ + tcp_ptr__ = (__force unsigned long)(_ptr); \ + lc_percpu = offsetof(struct lowcore, percpu_offset); \ + asm_inline volatile( \ + ALTERNATIVE("ag %[__ptr__],%[offzero](%%r0)\n", \ + "ag %[__ptr__],%[offalt](%%r0)\n", \ + ALT_FEATURE(MFEATURE_LOWCORE)) \ + : [__ptr__] "+d" (tcp_ptr__) \ + : [offzero] "i" (lc_percpu), \ + [offalt] "i" (lc_percpu + LOWCORE_ALT_ADDRESS), \ + "m" (((struct lowcore *)0)->percpu_offset) \ + : "cc"); \ + (TYPEOF_UNQUAL(*(_ptr)) __force __kernel *)tcp_ptr__; \ +}) + /* * We use a compare-and-swap loop since that uses less cpu cycles than * disabling and enabling interrupts like the generic variant would do. |