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Message-Id: <20241107190818.522639-16-ankur.a.arora@oracle.com>
Date: Thu, 7 Nov 2024 11:08:18 -0800
From: Ankur Arora <ankur.a.arora@...cle.com>
To: linux-pm@...r.kernel.org, kvm@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
linux-arch@...r.kernel.org
Cc: catalin.marinas@....com, will@...nel.org, tglx@...utronix.de,
mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com,
x86@...nel.org, hpa@...or.com, pbonzini@...hat.com,
vkuznets@...hat.com, rafael@...nel.org, daniel.lezcano@...aro.org,
peterz@...radead.org, arnd@...db.de, lenb@...nel.org,
mark.rutland@....com, harisokn@...zon.com, mtosatti@...hat.com,
sudeep.holla@....com, cl@...two.org, maz@...nel.org,
misono.tomohiro@...itsu.com, maobibo@...ngson.cn,
zhenglifeng1@...wei.com, joao.m.martins@...cle.com,
boris.ostrovsky@...cle.com, konrad.wilk@...cle.com
Subject: [RFC PATCH v9 15/15] arm64: support WFET in smp_cond_relaxed_timeout()
Support a WFET based implementation of the waited variant of
smp_cond_load_relaxed_timeout().
Signed-off-by: Ankur Arora <ankur.a.arora@...cle.com>
---
arch/arm64/include/asm/barrier.h | 12 ++++++++----
arch/arm64/include/asm/cmpxchg.h | 26 +++++++++++++++++---------
2 files changed, 25 insertions(+), 13 deletions(-)
diff --git a/arch/arm64/include/asm/barrier.h b/arch/arm64/include/asm/barrier.h
index ab2515ecd6ca..6fcec5c12c4d 100644
--- a/arch/arm64/include/asm/barrier.h
+++ b/arch/arm64/include/asm/barrier.h
@@ -12,6 +12,7 @@
#include <linux/kasan-checks.h>
#include <asm/alternative-macros.h>
+#include <asm/delay-const.h>
#define __nops(n) ".rept " #n "\nnop\n.endr\n"
#define nops(n) asm volatile(__nops(n))
@@ -198,7 +199,7 @@ do { \
VAL = READ_ONCE(*__PTR); \
if (cond_expr) \
break; \
- __cmpwait_relaxed(__PTR, VAL); \
+ __cmpwait_relaxed(__PTR, VAL, ~0UL); \
} \
(typeof(*ptr))VAL; \
})
@@ -211,7 +212,7 @@ do { \
VAL = smp_load_acquire(__PTR); \
if (cond_expr) \
break; \
- __cmpwait_relaxed(__PTR, VAL); \
+ __cmpwait_relaxed(__PTR, VAL, ~0UL); \
} \
(typeof(*ptr))VAL; \
})
@@ -241,11 +242,13 @@ do { \
({ \
typeof(ptr) __PTR = (ptr); \
__unqual_scalar_typeof(*ptr) VAL; \
+ const unsigned long __time_limit_cycles = \
+ NSECS_TO_CYCLES(time_limit_ns); \
for (;;) { \
VAL = READ_ONCE(*__PTR); \
if (cond_expr) \
break; \
- __cmpwait_relaxed(__PTR, VAL); \
+ __cmpwait_relaxed(__PTR, VAL, __time_limit_cycles); \
if ((time_expr_ns) >= time_limit_ns) \
break; \
} \
@@ -257,7 +260,8 @@ do { \
({ \
__unqual_scalar_typeof(*ptr) _val; \
\
- int __wfe = arch_timer_evtstrm_available(); \
+ int __wfe = arch_timer_evtstrm_available() || \
+ alternative_has_cap_unlikely(ARM64_HAS_WFXT); \
if (likely(__wfe)) \
_val = __smp_cond_load_timeout_wait(ptr, cond_expr, \
time_expr_ns, \
diff --git a/arch/arm64/include/asm/cmpxchg.h b/arch/arm64/include/asm/cmpxchg.h
index d7a540736741..bb842dab5d0e 100644
--- a/arch/arm64/include/asm/cmpxchg.h
+++ b/arch/arm64/include/asm/cmpxchg.h
@@ -210,7 +210,8 @@ __CMPXCHG_GEN(_mb)
#define __CMPWAIT_CASE(w, sfx, sz) \
static inline void __cmpwait_case_##sz(volatile void *ptr, \
- unsigned long val) \
+ unsigned long val, \
+ unsigned long time_limit_cycles) \
{ \
unsigned long tmp; \
\
@@ -220,10 +221,12 @@ static inline void __cmpwait_case_##sz(volatile void *ptr, \
" ldxr" #sfx "\t%" #w "[tmp], %[v]\n" \
" eor %" #w "[tmp], %" #w "[tmp], %" #w "[val]\n" \
" cbnz %" #w "[tmp], 1f\n" \
- " wfe\n" \
+ ALTERNATIVE("wfe\n", \
+ "msr s0_3_c1_c0_0, %[time_limit_cycles]\n", \
+ ARM64_HAS_WFXT) \
"1:" \
: [tmp] "=&r" (tmp), [v] "+Q" (*(u##sz *)ptr) \
- : [val] "r" (val)); \
+ : [val] "r" (val), [time_limit_cycles] "r" (time_limit_cycles));\
}
__CMPWAIT_CASE(w, b, 8);
@@ -236,17 +239,22 @@ __CMPWAIT_CASE( , , 64);
#define __CMPWAIT_GEN(sfx) \
static __always_inline void __cmpwait##sfx(volatile void *ptr, \
unsigned long val, \
+ unsigned long time_limit_cycles, \
int size) \
{ \
switch (size) { \
case 1: \
- return __cmpwait_case##sfx##_8(ptr, (u8)val); \
+ return __cmpwait_case##sfx##_8(ptr, (u8)val, \
+ time_limit_cycles); \
case 2: \
- return __cmpwait_case##sfx##_16(ptr, (u16)val); \
+ return __cmpwait_case##sfx##_16(ptr, (u16)val, \
+ time_limit_cycles); \
case 4: \
- return __cmpwait_case##sfx##_32(ptr, val); \
+ return __cmpwait_case##sfx##_32(ptr, val, \
+ time_limit_cycles); \
case 8: \
- return __cmpwait_case##sfx##_64(ptr, val); \
+ return __cmpwait_case##sfx##_64(ptr, val, \
+ time_limit_cycles); \
default: \
BUILD_BUG(); \
} \
@@ -258,7 +266,7 @@ __CMPWAIT_GEN()
#undef __CMPWAIT_GEN
-#define __cmpwait_relaxed(ptr, val) \
- __cmpwait((ptr), (unsigned long)(val), sizeof(*(ptr)))
+#define __cmpwait_relaxed(ptr, val, time_limit_cycles) \
+ __cmpwait((ptr), (unsigned long)(val), time_limit_cycles, sizeof(*(ptr)))
#endif /* __ASM_CMPXCHG_H */
--
2.43.5
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