diff options
author | Alexandre Ghiti <alexghiti@rivosinc.com> | 2024-11-03 15:51:46 +0100 |
---|---|---|
committer | Palmer Dabbelt <palmer@rivosinc.com> | 2024-11-11 16:33:13 +0100 |
commit | 6116e22ef33a8239f3d53bb25377e9ed733c4176 (patch) | |
tree | ad8f8c9ea81fded5b2cae3f1213d0f8ddc648b73 /arch/riscv | |
parent | riscv: Implement cmpxchg8/16() using Zabha (diff) | |
download | linux-6116e22ef33a8239f3d53bb25377e9ed733c4176.tar.xz linux-6116e22ef33a8239f3d53bb25377e9ed733c4176.zip |
riscv: Improve zacas fully-ordered cmpxchg()
The current fully-ordered cmpxchgXX() implementation results in:
amocas.X.rl a5,a4,(s1)
fence rw,rw
This provides enough sync but we can actually use the following better
mapping instead:
amocas.X.aqrl a5,a4,(s1)
Suggested-by: Andrea Parri <andrea@rivosinc.com>
Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Andrea Parri <parri.andrea@gmail.com>
Link: https://lore.kernel.org/r/20241103145153.105097-7-alexghiti@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Diffstat (limited to 'arch/riscv')
-rw-r--r-- | arch/riscv/include/asm/cmpxchg.h | 92 |
1 files changed, 64 insertions, 28 deletions
diff --git a/arch/riscv/include/asm/cmpxchg.h b/arch/riscv/include/asm/cmpxchg.h index 1f4cd12e4664..052418aba11a 100644 --- a/arch/riscv/include/asm/cmpxchg.h +++ b/arch/riscv/include/asm/cmpxchg.h @@ -107,8 +107,10 @@ * store NEW in MEM. Return the initial value in MEM. Success is * indicated by comparing RETURN with OLD. */ - -#define __arch_cmpxchg_masked(sc_sfx, cas_sfx, prepend, append, r, p, o, n) \ +#define __arch_cmpxchg_masked(sc_sfx, cas_sfx, \ + sc_prepend, sc_append, \ + cas_prepend, cas_append, \ + r, p, o, n) \ ({ \ if (IS_ENABLED(CONFIG_RISCV_ISA_ZABHA) && \ IS_ENABLED(CONFIG_RISCV_ISA_ZACAS) && \ @@ -117,9 +119,9 @@ r = o; \ \ __asm__ __volatile__ ( \ - prepend \ + cas_prepend \ " amocas" cas_sfx " %0, %z2, %1\n" \ - append \ + cas_append \ : "+&r" (r), "+A" (*(p)) \ : "rJ" (n) \ : "memory"); \ @@ -134,7 +136,7 @@ ulong __rc; \ \ __asm__ __volatile__ ( \ - prepend \ + sc_prepend \ "0: lr.w %0, %2\n" \ " and %1, %0, %z5\n" \ " bne %1, %z3, 1f\n" \ @@ -142,7 +144,7 @@ " or %1, %1, %z4\n" \ " sc.w" sc_sfx " %1, %1, %2\n" \ " bnez %1, 0b\n" \ - append \ + sc_append \ "1:\n" \ : "=&r" (__retx), "=&r" (__rc), "+A" (*(__ptr32b)) \ : "rJ" ((long)__oldx), "rJ" (__newx), \ @@ -153,16 +155,19 @@ } \ }) -#define __arch_cmpxchg(lr_sfx, sc_cas_sfx, prepend, append, r, p, co, o, n) \ +#define __arch_cmpxchg(lr_sfx, sc_sfx, cas_sfx, \ + sc_prepend, sc_append, \ + cas_prepend, cas_append, \ + r, p, co, o, n) \ ({ \ if (IS_ENABLED(CONFIG_RISCV_ISA_ZACAS) && \ riscv_has_extension_unlikely(RISCV_ISA_EXT_ZACAS)) { \ r = o; \ \ __asm__ __volatile__ ( \ - prepend \ - " amocas" sc_cas_sfx " %0, %z2, %1\n" \ - append \ + cas_prepend \ + " amocas" cas_sfx " %0, %z2, %1\n" \ + cas_append \ : "+&r" (r), "+A" (*(p)) \ : "rJ" (n) \ : "memory"); \ @@ -170,12 +175,12 @@ register unsigned int __rc; \ \ __asm__ __volatile__ ( \ - prepend \ + sc_prepend \ "0: lr" lr_sfx " %0, %2\n" \ " bne %0, %z3, 1f\n" \ - " sc" sc_cas_sfx " %1, %z4, %2\n" \ + " sc" sc_sfx " %1, %z4, %2\n" \ " bnez %1, 0b\n" \ - append \ + sc_append \ "1:\n" \ : "=&r" (r), "=&r" (__rc), "+A" (*(p)) \ : "rJ" (co o), "rJ" (n) \ @@ -183,7 +188,9 @@ } \ }) -#define _arch_cmpxchg(ptr, old, new, sc_cas_sfx, prepend, append) \ +#define _arch_cmpxchg(ptr, old, new, sc_sfx, cas_sfx, \ + sc_prepend, sc_append, \ + cas_prepend, cas_append) \ ({ \ __typeof__(ptr) __ptr = (ptr); \ __typeof__(*(__ptr)) __old = (old); \ @@ -192,22 +199,28 @@ \ switch (sizeof(*__ptr)) { \ case 1: \ - __arch_cmpxchg_masked(sc_cas_sfx, ".b" sc_cas_sfx, \ - prepend, append, \ - __ret, __ptr, __old, __new); \ + __arch_cmpxchg_masked(sc_sfx, ".b" cas_sfx, \ + sc_prepend, sc_append, \ + cas_prepend, cas_append, \ + __ret, __ptr, __old, __new); \ break; \ case 2: \ - __arch_cmpxchg_masked(sc_cas_sfx, ".h" sc_cas_sfx, \ - prepend, append, \ - __ret, __ptr, __old, __new); \ + __arch_cmpxchg_masked(sc_sfx, ".h" cas_sfx, \ + sc_prepend, sc_append, \ + cas_prepend, cas_append, \ + __ret, __ptr, __old, __new); \ break; \ case 4: \ - __arch_cmpxchg(".w", ".w" sc_cas_sfx, prepend, append, \ - __ret, __ptr, (long), __old, __new); \ + __arch_cmpxchg(".w", ".w" sc_sfx, ".w" cas_sfx, \ + sc_prepend, sc_append, \ + cas_prepend, cas_append, \ + __ret, __ptr, (long), __old, __new); \ break; \ case 8: \ - __arch_cmpxchg(".d", ".d" sc_cas_sfx, prepend, append, \ - __ret, __ptr, /**/, __old, __new); \ + __arch_cmpxchg(".d", ".d" sc_sfx, ".d" cas_sfx, \ + sc_prepend, sc_append, \ + cas_prepend, cas_append, \ + __ret, __ptr, /**/, __old, __new); \ break; \ default: \ BUILD_BUG(); \ @@ -215,17 +228,40 @@ (__typeof__(*(__ptr)))__ret; \ }) +/* + * These macros are here to improve the readability of the arch_cmpxchg_XXX() + * macros. + */ +#define SC_SFX(x) x +#define CAS_SFX(x) x +#define SC_PREPEND(x) x +#define SC_APPEND(x) x +#define CAS_PREPEND(x) x +#define CAS_APPEND(x) x + #define arch_cmpxchg_relaxed(ptr, o, n) \ - _arch_cmpxchg((ptr), (o), (n), "", "", "") + _arch_cmpxchg((ptr), (o), (n), \ + SC_SFX(""), CAS_SFX(""), \ + SC_PREPEND(""), SC_APPEND(""), \ + CAS_PREPEND(""), CAS_APPEND("")) #define arch_cmpxchg_acquire(ptr, o, n) \ - _arch_cmpxchg((ptr), (o), (n), "", "", RISCV_ACQUIRE_BARRIER) + _arch_cmpxchg((ptr), (o), (n), \ + SC_SFX(""), CAS_SFX(""), \ + SC_PREPEND(""), SC_APPEND(RISCV_ACQUIRE_BARRIER), \ + CAS_PREPEND(""), CAS_APPEND(RISCV_ACQUIRE_BARRIER)) #define arch_cmpxchg_release(ptr, o, n) \ - _arch_cmpxchg((ptr), (o), (n), "", RISCV_RELEASE_BARRIER, "") + _arch_cmpxchg((ptr), (o), (n), \ + SC_SFX(""), CAS_SFX(""), \ + SC_PREPEND(RISCV_RELEASE_BARRIER), SC_APPEND(""), \ + CAS_PREPEND(RISCV_RELEASE_BARRIER), CAS_APPEND("")) #define arch_cmpxchg(ptr, o, n) \ - _arch_cmpxchg((ptr), (o), (n), ".rl", "", " fence rw, rw\n") + _arch_cmpxchg((ptr), (o), (n), \ + SC_SFX(".rl"), CAS_SFX(".aqrl"), \ + SC_PREPEND(""), SC_APPEND(RISCV_FULL_BARRIER), \ + CAS_PREPEND(""), CAS_APPEND("")) #define arch_cmpxchg_local(ptr, o, n) \ arch_cmpxchg_relaxed((ptr), (o), (n)) |