[RFC PATCH 08/13] arm64: percpu: Implement preemptible void RMW ops

[Mark Rutland]

Use the PCPU GPR infrastructure to implement all of the RMW ops which do not
return a value.

Generated code before this patch (v7.2-rc4):

| <outline_this_cpu_add_u64>:
|        paciasp
|        stp     x29, x30, [sp, #-16]!
|        mrs     x2, sp_el0
|        mov     x29, sp
|        ldr     w3, [x2, #8]
|        add     w3, w3, #0x1
|        str     w3, [x2, #8]
|        mrs     x3, tpidr_el1
|        add     x0, x0, x3
| 1:     ldxr    x5, [x0]
|        add     x5, x5, x1
|        stxr    w4, x5, [x0]
|        cbnz    w4, 1b
|        ldr     x0, [x2, #8]
|        sub     x0, x0, #0x1
|        str     w0, [x2, #8]
|        cbz     x0, 2f
|        ldr     x0, [x2, #8]
|        cbnz    x0, 3f
| 2:     bl      preempt_schedule_notrace
| 3:     ldp     x29, x30, [sp], #16
|        autiasp
|        ret

Generated code after this patch:

| <outline_this_cpu_add_u64>:
|        mrs     x2, sp_el0
|        mov     w4, #0xc80
|        strh    w4, [x2, #20]
|        mrs     x4, tpidr_el1
|        add     x3, x0, x4
| 1:     ldxr    x6, [x3]
|        add     x6, x6, x1
|        stxr    w5, x6, [x3]
|        cbnz    w5, 1b
|        strh    wzr, [x2, #20]
|        ret

Signed-off-by: Mark Rutland <mark.rutland at arm.com>
Cc: Ada Couprie Diaz <ada.coupriediaz at arm.com>
Cc: Ard Biesheuvel <ardb at kernel.org>
Cc: Catalin Marinas <catalin.marinas at arm.com>
Cc: Jinjie Ruan <ruanjinjie at huawei.com>
Cc: Marc Zyngier <maz at kernel.org>
Cc: Peter Zijlstra <peterz at infradead.org>
Cc: Vladimir Murzin <vladimir.murzin at arm.com>
Cc: Will Deacon <will at kernel.org>
Cc: Yang Shi <yang at os.amperecomputing.com>
---
 arch/arm64/include/asm/percpu.h | 52 ++++++++++++++++++++-------------
 1 file changed, 32 insertions(+), 20 deletions(-)

diff --git a/arch/arm64/include/asm/percpu.h b/arch/arm64/include/asm/percpu.h
index 32623ea676b96..7e9ab51561706 100644
--- a/arch/arm64/include/asm/percpu.h
+++ b/arch/arm64/include/asm/percpu.h
@@ -140,23 +140,35 @@ static inline void __percpu_write_##sz(void __percpu *pcp, unsigned long val)	\
 
 #define __PERCPU_OP_CASE(w, sfx, name, sz, op_llsc, op_lse)		\
 static inline void							\
-__percpu_##name##_case_##sz(void *ptr, unsigned long val)		\
+__percpu_##name##_case_##sz(void __percpu *pcp, unsigned long val)	\
 {									\
+	u16 *gprs = &current_thread_info()->pcpu_gprs;			\
+	unsigned long addr;						\
+	unsigned long off;						\
 	unsigned int loop;						\
 	u##sz tmp;							\
 									\
-	asm volatile (ARM64_LSE_ATOMIC_INSN(				\
+	asm volatile (							\
+	__PCPU_GPRS_BEGIN("%[gprs]", "%[pcp]", "%[off]", "%[addr]")	\
+	ARM64_LSE_ATOMIC_INSN(						\
 	/* LL/SC */							\
-	"1:	ldxr" #sfx "\t%" #w "[tmp], %[ptr]\n"			\
+	"1:	ldxr" #sfx "\t%" #w "[tmp], [%[addr]]\n"		\
 		#op_llsc "\t%" #w "[tmp], %" #w "[tmp], %" #w "[val]\n"	\
-	"	stxr" #sfx "\t%w[loop], %" #w "[tmp], %[ptr]\n"		\
+	"	stxr" #sfx "\t%w[loop], %" #w "[tmp], [%[addr]]\n"	\
 	"	cbnz	%w[loop], 1b",					\
 	/* LSE atomics */						\
-		#op_lse "\t%" #w "[val], %" #w "[tmp], %[ptr]\n"	\
+		#op_lse "\t%" #w "[val], %" #w "[tmp], [%[addr]]\n"	\
 		__nops(3))						\
-	: [loop] "=&r" (loop), [tmp] "=&r" (tmp),			\
-	  [ptr] "+Q"(*(u##sz *)ptr)					\
-	: [val] "r" ((u##sz)(val)));					\
+	__PCPU_GPRS_END("%[gprs]")					\
+	: [gprs] "=Qo" (*gprs),						\
+	  [addr] "=&r" (addr),						\
+	  [off] "=&r" (off),						\
+	  [loop] "=&r" (loop),						\
+	  [tmp] "=&r" (tmp)						\
+	: [pcp] "r" (pcp),						\
+	  [val] "r" ((u##sz)(val))					\
+	: "memory"							\
+	);								\
 }
 
 #define __PERCPU_RET_OP_CASE(w, sfx, name, sz, op_llsc, op_lse)		\
@@ -273,13 +285,13 @@ PERCPU_RET_OP(add, add, ldadd)
 	_pcp_wrap(__percpu_write_64, pcp, (unsigned long)val)
 
 #define this_cpu_add_1(pcp, val)	\
-	_pcp_protect(__percpu_add_case_8, pcp, val)
+	_pcp_wrap(__percpu_add_case_8, pcp, val)
 #define this_cpu_add_2(pcp, val)	\
-	_pcp_protect(__percpu_add_case_16, pcp, val)
+	_pcp_wrap(__percpu_add_case_16, pcp, val)
 #define this_cpu_add_4(pcp, val)	\
-	_pcp_protect(__percpu_add_case_32, pcp, val)
+	_pcp_wrap(__percpu_add_case_32, pcp, val)
 #define this_cpu_add_8(pcp, val)	\
-	_pcp_protect(__percpu_add_case_64, pcp, val)
+	_pcp_wrap(__percpu_add_case_64, pcp, val)
 
 #define this_cpu_add_return_1(pcp, val)	\
 	_pcp_protect_return(__percpu_add_return_case_8, pcp, val)
@@ -291,22 +303,22 @@ PERCPU_RET_OP(add, add, ldadd)
 	_pcp_protect_return(__percpu_add_return_case_64, pcp, val)
 
 #define this_cpu_and_1(pcp, val)	\
-	_pcp_protect(__percpu_andnot_case_8, pcp, ~val)
+	_pcp_wrap(__percpu_andnot_case_8, pcp, ~val)
 #define this_cpu_and_2(pcp, val)	\
-	_pcp_protect(__percpu_andnot_case_16, pcp, ~val)
+	_pcp_wrap(__percpu_andnot_case_16, pcp, ~val)
 #define this_cpu_and_4(pcp, val)	\
-	_pcp_protect(__percpu_andnot_case_32, pcp, ~val)
+	_pcp_wrap(__percpu_andnot_case_32, pcp, ~val)
 #define this_cpu_and_8(pcp, val)	\
-	_pcp_protect(__percpu_andnot_case_64, pcp, ~val)
+	_pcp_wrap(__percpu_andnot_case_64, pcp, ~val)
 
 #define this_cpu_or_1(pcp, val)		\
-	_pcp_protect(__percpu_or_case_8, pcp, val)
+	_pcp_wrap(__percpu_or_case_8, pcp, val)
 #define this_cpu_or_2(pcp, val)		\
-	_pcp_protect(__percpu_or_case_16, pcp, val)
+	_pcp_wrap(__percpu_or_case_16, pcp, val)
 #define this_cpu_or_4(pcp, val)		\
-	_pcp_protect(__percpu_or_case_32, pcp, val)
+	_pcp_wrap(__percpu_or_case_32, pcp, val)
 #define this_cpu_or_8(pcp, val)		\
-	_pcp_protect(__percpu_or_case_64, pcp, val)
+	_pcp_wrap(__percpu_or_case_64, pcp, val)
 
 #define this_cpu_xchg_1(pcp, val)	\
 	_pcp_protect_return(xchg_relaxed, pcp, val)
-- 
2.30.2