[PATCH v2 05/10] percpu: Wire up cmpxchg128

Peter Zijlstra
2023-02-02T15:31:14Z

In order to replace cmpxchg_double() with the newly minted
cmpxchg128() family of functions, wire it up in this_cpu_cmpxchg().

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
arch/arm64/include/asm/percpu.h | 21 +++++++++++++++
arch/s390/include/asm/percpu.h | 17 ++++++++++++
arch/x86/include/asm/percpu.h | 56 ++++++++++++++++++++++++++++++++++++++++
include/asm-generic/percpu.h | 8 +++++
include/linux/percpu-defs.h | 20 ++++++++++++--
5 files changed, 120 insertions(+), 2 deletions(-)

--- a/arch/arm64/include/asm/percpu.h
+++ b/arch/arm64/include/asm/percpu.h
@@ -140,6 +140,10 @@ PERCPU_RET_OP(add, add, ldadd)
* re-enabling preemption for preemptible kernels, but doing that in a way
* which builds inside a module would mean messing directly with the preempt
* count. If you do this, peterz and tglx will hunt you down.
+ *
+ * Not to mention it'll break the actual preemption model for missing a
+ * preemption point when TIF_NEED_RESCHED gets set while preemption is
+ * disabled.
*/
#define this_cpu_cmpxchg_double_8(ptr1, ptr2, o1, o2, n1, n2) \
({ \
@@ -240,6 +244,23 @@ PERCPU_RET_OP(add, add, ldadd)
#define this_cpu_cmpxchg_8(pcp, o, n) \
_pcp_protect_return(cmpxchg_relaxed, pcp, o, n)

+#define this_cpu_cmpxchg_16(pcp, o, n) \
+({ \
+ typedef typeof(pcp) pcp_op_T__; \
+ union { \
+ pcp_op_T__ pot; \
+ u128 val; \
+ } old__, new__, ret__; \
+ pcp_op_T__ *ptr__; \
+ old__.pot = o; \
+ new__.pot = n; \
+ preempt_disable_notrace(); \
+ ptr__ = raw_cpu_ptr(&(pcp)); \
+ ret__.val = cmpxchg128_local((void *)ptr__, old__.val, new__.val); \
+ preempt_enable_notrace(); \
+ ret__.pot; \
+})
+
#ifdef __KVM_NVHE_HYPERVISOR__
extern unsigned long __hyp_per_cpu_offset(unsigned int cpu);
#define __per_cpu_offset
--- a/arch/s390/include/asm/percpu.h
+++ b/arch/s390/include/asm/percpu.h
@@ -148,6 +148,23 @@
#define this_cpu_cmpxchg_4(pcp, oval, nval) arch_this_cpu_cmpxchg(pcp, oval, nval)
#define this_cpu_cmpxchg_8(pcp, oval, nval) arch_this_cpu_cmpxchg(pcp, oval, nval)

+#define this_cpu_cmpxchg_16(pcp, oval, nval) \
+({ \
+ typedef typeof(pcp) pcp_op_T__; \
+ union { \
+ pcp_op_T__ pot; \
+ u128 val; \
+ } old__, new__, ret__; \
+ pcp_op_T__ *ptr__; \
+ old__.pot = oval; \
+ new__.pot = nval; \
+ preempt_disable_notrace(); \
+ ptr__ = raw_cpu_ptr(&(pcp)); \
+ ret__.val = cmpxchg128((void *)ptr__, old__.val, new__.val); \
+ preempt_enable_notrace(); \
+ ret__.pot; \
+})
+
#define arch_this_cpu_xchg(pcp, nval) \
({ \
typeof(pcp) *ptr__; \
--- a/arch/x86/include/asm/percpu.h
+++ b/arch/x86/include/asm/percpu.h
@@ -210,6 +210,62 @@ do { \
(typeof(_var))(unsigned long) pco_old__; \
})

+#if defined(CONFIG_X86_32) && defined(CONFIG_X86_CMPXCHG64)
+#define percpu_cmpxchg64_op(size, qual, _var, _oval, _nval) \
+({ \
+ union { \
+ typeof(_var) var; \
+ struct { \
+ u32 low, high; \
+ }; \
+ } old__, new__; \
+ \
+ old__.var = _oval; \
+ new__.var = _nval; \
+ \
+ asm qual ("cmpxchg8b " __percpu_arg([var]) \
+ : [var] "+m" (_var), \
+ "+a" (old__.low), \
+ "+d" (old__.high) \
+ : "b" (new__.low), \
+ "c" (new__.high) \
+ : "memory"); \
+ \
+ old__.var; \
+})
+
+#define raw_cpu_cmpxchg_8(pcp, oval, nval) percpu_cmpxchg64_op(8, , pcp, oval, nval)
+#define this_cpu_cmpxchg_8(pcp, oval, nval) percpu_cmpxchg64_op(8, volatile, pcp, oval, nval)
+#endif
+
+#ifdef CONFIG_X86_64
+#define percpu_cmpxchg128_op(size, qual, _var, _oval, _nval) \
+({ \
+ union { \
+ typeof(_var) var; \
+ struct { \
+ u64 low, high; \
+ }; \
+ } old__, new__; \
+ \
+ old__.var = _oval; \
+ new__.var = _nval; \
+ \
+ asm qual ("cmpxchg16b " __percpu_arg([var]) \
+ : [var] "+m" (_var), \
+ "+a" (old__.low), \
+ "+d" (old__.high) \
+ : "b" (new__.low), \
+ "c" (new__.high) \
+ : "memory"); \
+ \
+ old__.var; \
+})
+
+#define raw_cpu_cmpxchg_16(pcp, oval, nval) percpu_cmpxchg128_op(16, , pcp, oval, nval)
+#define this_cpu_cmpxchg_16(pcp, oval, nval) percpu_cmpxchg128_op(16, volatile, pcp, oval, nval)
+#endif
+
/*
* this_cpu_read() makes gcc load the percpu variable every time it is
* accessed while this_cpu_read_stable() allows the value to be cached.
--- a/include/asm-generic/percpu.h
+++ b/include/asm-generic/percpu.h
@@ -298,6 +298,10 @@ do { \
#define raw_cpu_cmpxchg_8(pcp, oval, nval) \
raw_cpu_generic_cmpxchg(pcp, oval, nval)
#endif
+#ifndef raw_cpu_cmpxchg_16
+#define raw_cpu_cmpxchg_16(pcp, oval, nval) \
+ raw_cpu_generic_cmpxchg(pcp, oval, nval)
+#endif

#ifndef raw_cpu_cmpxchg_double_1
#define raw_cpu_cmpxchg_double_1(pcp1, pcp2, oval1, oval2, nval1, nval2) \
@@ -423,6 +427,10 @@ do { \
#define this_cpu_cmpxchg_8(pcp, oval, nval) \
this_cpu_generic_cmpxchg(pcp, oval, nval)
#endif
+#ifndef this_cpu_cmpxchg_16
+#define this_cpu_cmpxchg_16(pcp, oval, nval) \
+ this_cpu_generic_cmpxchg(pcp, oval, nval)
+#endif

#ifndef this_cpu_cmpxchg_double_1
#define this_cpu_cmpxchg_double_1(pcp1, pcp2, oval1, oval2, nval1, nval2) \
--- a/include/linux/percpu-defs.h
+++ b/include/linux/percpu-defs.h
@@ -343,6 +343,22 @@ static inline void __this_cpu_preempt_ch
pscr2_ret__; \
})

+#define __pcpu_size16_call_return2(stem, variable, ...) \
+({ \
+ typeof(variable) pscr2_ret__; \
+ __verify_pcpu_ptr(&(variable)); \
+ switch(sizeof(variable)) { \
+ case 1: pscr2_ret__ = stem##1(variable, __VA_ARGS__); break; \
+ case 2: pscr2_ret__ = stem##2(variable, __VA_ARGS__); break; \
+ case 4: pscr2_ret__ = stem##4(variable, __VA_ARGS__); break; \
+ case 8: pscr2_ret__ = stem##8(variable, __VA_ARGS__); break; \
+ case 16: pscr2_ret__ = stem##16(variable, __VA_ARGS__); break; \
+ default: \
+ __bad_size_call_parameter(); break; \
+ } \
+ pscr2_ret__; \
+})
+
/*
* Special handling for cmpxchg_double. cmpxchg_double is passed two
* percpu variables. The first has to be aligned to a double word
@@ -425,7 +441,7 @@ do { \
#define raw_cpu_add_return(pcp, val) __pcpu_size_call_return2(raw_cpu_add_return_, pcp, val)
#define raw_cpu_xchg(pcp, nval) __pcpu_size_call_return2(raw_cpu_xchg_, pcp, nval)
#define raw_cpu_cmpxchg(pcp, oval, nval) \
- __pcpu_size_call_return2(raw_cpu_cmpxchg_, pcp, oval, nval)
+ __pcpu_size16_call_return2(raw_cpu_cmpxchg_, pcp, oval, nval)
#define raw_cpu_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2) \
__pcpu_double_call_return_bool(raw_cpu_cmpxchg_double_, pcp1, pcp2, oval1, oval2, nval1, nval2)

@@ -512,7 +528,7 @@ do { \
#define this_cpu_add_return(pcp, val) __pcpu_size_call_return2(this_cpu_add_return_, pcp, val)
#define this_cpu_xchg(pcp, nval) __pcpu_size_call_return2(this_cpu_xchg_, pcp, nval)
#define this_cpu_cmpxchg(pcp, oval, nval) \
- __pcpu_size_call_return2(this_cpu_cmpxchg_, pcp, oval, nval)
+ __pcpu_size16_call_return2(this_cpu_cmpxchg_, pcp, oval, nval)
#define this_cpu_cmpxchg_double(pcp1, pcp2, oval1, oval2, nval1, nval2) \
__pcpu_double_call_return_bool(this_cpu_cmpxchg_double_, pcp1, pcp2, oval1, oval2, nval1, nval2)