[PATCH v3 03/11] arch: Introduce arch_{,try_}_cmpxchg128{,_local}()

Peter Zijlstra
2023-05-15T08:07:36Z

For all architectures that currently support cmpxchg_double()
implement the cmpxchg128() family of functions that is basically the
same but with a saner interface.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Heiko Carstens <hca@linux.ibm.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
---
arch/arm64/include/asm/atomic_ll_sc.h | 41 +++++++++++++++++++++
arch/arm64/include/asm/atomic_lse.h | 31 ++++++++++++++++
arch/arm64/include/asm/cmpxchg.h | 26 +++++++++++++
arch/s390/include/asm/cmpxchg.h | 14 +++++++
arch/x86/include/asm/cmpxchg_32.h | 3 +
arch/x86/include/asm/cmpxchg_64.h | 64 +++++++++++++++++++++++++++++++++-
6 files changed, 177 insertions(+), 2 deletions(-)

--- a/arch/arm64/include/asm/atomic_ll_sc.h
+++ b/arch/arm64/include/asm/atomic_ll_sc.h
@@ -326,6 +326,47 @@ __CMPXCHG_DBL( , , , )
__CMPXCHG_DBL(_mb, dmb ish, l, "memory")

#undef __CMPXCHG_DBL
+
+union __u128_halves {
+ u128 full;
+ struct {
+ u64 low, high;
+ };
+};
+
+#define __CMPXCHG128(name, mb, rel, cl...) \
+static __always_inline u128 \
+__ll_sc__cmpxchg128##name(volatile u128 *ptr, u128 old, u128 new) \
+{ \
+ union __u128_halves r, o = { .full = (old) }, \
+ n = { .full = (new) }; \
+ unsigned int tmp; \
+ \
+ asm volatile("// __cmpxchg128" #name "\n" \
+ " prfm pstl1strm, %[v]\n" \
+ "1: ldxp %[rl], %[rh], %[v]\n" \
+ " cmp %[rl], %[ol]\n" \
+ " ccmp %[rh], %[oh], 0, eq\n" \
+ " b.ne 2f\n" \
+ " st" #rel "xp %w[tmp], %[nl], %[nh], %[v]\n" \
+ " cbnz %w[tmp], 1b\n" \
+ " " #mb "\n" \
+ "2:" \
+ : [v] "+Q" (*(u128 *)ptr), \
+ [rl] "=&r" (r.low), [rh] "=&r" (r.high), \
+ [tmp] "=&r" (tmp) \
+ : [ol] "r" (o.low), [oh] "r" (o.high), \
+ [nl] "r" (n.low), [nh] "r" (n.high) \
+ : "cc", ##cl); \
+ \
+ return r.full; \
+}
+
+__CMPXCHG128( , , )
+__CMPXCHG128(_mb, dmb ish, l, "memory")
+
+#undef __CMPXCHG128
+
#undef K

#endif /* __ASM_ATOMIC_LL_SC_H */
--- a/arch/arm64/include/asm/atomic_lse.h
+++ b/arch/arm64/include/asm/atomic_lse.h
@@ -317,4 +317,35 @@ __CMPXCHG_DBL(_mb, al, "memory")

#undef __CMPXCHG_DBL

+#define __CMPXCHG128(name, mb, cl...) \
+static __always_inline u128 \
+__lse__cmpxchg128##name(volatile u128 *ptr, u128 old, u128 new) \
+{ \
+ union __u128_halves r, o = { .full = (old) }, \
+ n = { .full = (new) }; \
+ register unsigned long x0 asm ("x0") = o.low; \
+ register unsigned long x1 asm ("x1") = o.high; \
+ register unsigned long x2 asm ("x2") = n.low; \
+ register unsigned long x3 asm ("x3") = n.high; \
+ register unsigned long x4 asm ("x4") = (unsigned long)ptr; \
+ \
+ asm volatile( \
+ __LSE_PREAMBLE \
+ " casp" #mb "\t%[old1], %[old2], %[new1], %[new2], %[v]\n"\
+ : [old1] "+&r" (x0), [old2] "+&r" (x1), \
+ [v] "+Q" (*(u128 *)ptr) \
+ : [new1] "r" (x2), [new2] "r" (x3), [ptr] "r" (x4), \
+ [oldval1] "r" (o.low), [oldval2] "r" (o.high) \
+ : cl); \
+ \
+ r.low = x0; r.high = x1; \
+ \
+ return r.full; \
+}
+
+__CMPXCHG128( , )
+__CMPXCHG128(_mb, al, "memory")
+
+#undef __CMPXCHG128
+
#endif /* __ASM_ATOMIC_LSE_H */
--- a/arch/arm64/include/asm/cmpxchg.h
+++ b/arch/arm64/include/asm/cmpxchg.h
@@ -146,6 +146,19 @@ __CMPXCHG_DBL(_mb)

#undef __CMPXCHG_DBL

+#define __CMPXCHG128(name) \
+static inline u128 __cmpxchg128##name(volatile u128 *ptr, \
+ u128 old, u128 new) \
+{ \
+ return __lse_ll_sc_body(_cmpxchg128##name, \
+ ptr, old, new); \
+}
+
+__CMPXCHG128( )
+__CMPXCHG128(_mb)
+
+#undef __CMPXCHG128
+
#define __CMPXCHG_GEN(sfx) \
static __always_inline unsigned long __cmpxchg##sfx(volatile void *ptr, \
unsigned long old, \
@@ -228,6 +241,19 @@ __CMPXCHG_GEN(_mb)
__ret; \
})

+/* cmpxchg128 */
+#define system_has_cmpxchg128() 1
+
+#define arch_cmpxchg128(ptr, o, n) \
+({ \
+ __cmpxchg128_mb((ptr), (o), (n)); \
+})
+
+#define arch_cmpxchg128_local(ptr, o, n) \
+({ \
+ __cmpxchg128((ptr), (o), (n)); \
+})
+
#define __CMPWAIT_CASE(w, sfx, sz) \
static inline void __cmpwait_case_##sz(volatile void *ptr, \
unsigned long val) \
--- a/arch/s390/include/asm/cmpxchg.h
+++ b/arch/s390/include/asm/cmpxchg.h
@@ -224,4 +224,18 @@ static __always_inline int __cmpxchg_dou
(unsigned long)(n1), (unsigned long)(n2)); \
})

+#define system_has_cmpxchg128() 1
+
+static __always_inline u128 arch_cmpxchg128(volatile u128 *ptr, u128 old, u128 new)
+{
+ asm volatile(
+ " cdsg %[old],%[new],%[ptr]\n"
+ : [old] "+d" (old), [ptr] "+QS" (*ptr)
+ : [new] "d" (new)
+ : "memory", "cc");
+ return old;
+}
+
+#define arch_cmpxchg128 arch_cmpxchg128
+
#endif /* __ASM_CMPXCHG_H */
--- a/arch/x86/include/asm/cmpxchg_32.h
+++ b/arch/x86/include/asm/cmpxchg_32.h
@@ -103,6 +103,7 @@ static inline bool __try_cmpxchg64(volat

#endif

-#define system_has_cmpxchg_double() boot_cpu_has(X86_FEATURE_CX8)
+#define system_has_cmpxchg_double() boot_cpu_has(X86_FEATURE_CX8)
+#define system_has_cmpxchg64() boot_cpu_has(X86_FEATURE_CX8)

#endif /* _ASM_X86_CMPXCHG_32_H */
--- a/arch/x86/include/asm/cmpxchg_64.h
+++ b/arch/x86/include/asm/cmpxchg_64.h
@@ -20,6 +20,68 @@
arch_try_cmpxchg((ptr), (po), (n)); \
})

-#define system_has_cmpxchg_double() boot_cpu_has(X86_FEATURE_CX16)
+union __u128_halves {
+ u128 full;
+ struct {
+ u64 low, high;
+ };
+};
+
+#define __arch_cmpxchg128(_ptr, _old, _new, _lock) \
+({ \
+ union __u128_halves o = { .full = (_old), }, \
+ n = { .full = (_new), }; \
+ \
+ asm volatile(_lock "cmpxchg16b %[ptr]" \
+ : [ptr] "+m" (*(_ptr)), \
+ "+a" (o.low), "+d" (o.high) \
+ : "b" (n.low), "c" (n.high) \
+ : "memory"); \
+ \
+ o.full; \
+})
+
+static __always_inline u128 arch_cmpxchg128(volatile u128 *ptr, u128 old, u128 new)
+{
+ return __arch_cmpxchg128(ptr, old, new, LOCK_PREFIX);
+}
+
+static __always_inline u128 arch_cmpxchg128_local(volatile u128 *ptr, u128 old, u128 new)
+{
+ return __arch_cmpxchg128(ptr, old, new,);
+}
+
+#define __arch_try_cmpxchg128(_ptr, _oldp, _new, _lock) \
+({ \
+ union __u128_halves o = { .full = *(_oldp), }, \
+ n = { .full = (_new), }; \
+ bool ret; \
+ \
+ asm volatile(_lock "cmpxchg16b %[ptr]" \
+ CC_SET(e) \
+ : CC_OUT(e) (ret), \
+ [ptr] "+m" (*ptr), \
+ "+a" (o.low), "+d" (o.high) \
+ : "b" (n.low), "c" (n.high) \
+ : "memory"); \
+ \
+ if (unlikely(!ret)) \
+ *(_oldp) = o.full; \
+ \
+ likely(ret); \
+})
+
+static __always_inline bool arch_try_cmpxchg128(volatile u128 *ptr, u128 *oldp, u128 new)
+{
+ return __arch_try_cmpxchg128(ptr, oldp, new, LOCK_PREFIX);
+}
+
+static __always_inline bool arch_try_cmpxchg128_local(volatile u128 *ptr, u128 *oldp, u128 new)
+{
+ return __arch_try_cmpxchg128(ptr, oldp, new,);
+}
+
+#define system_has_cmpxchg_double() boot_cpu_has(X86_FEATURE_CX16)
+#define system_has_cmpxchg128() boot_cpu_has(X86_FEATURE_CX16)

#endif /* _ASM_X86_CMPXCHG_64_H */