Re: [PATCH v2 06/10] riscv: Implement xchg8/16() using Zabha

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On 27/06/2024 15:45, Andrea Parri wrote:
-#define __arch_xchg_masked(sc_sfx, prepend, append, r, p, n)		\
+#define __arch_xchg_masked(sc_sfx, swap_sfx, prepend, sc_append,	\
+			   swap_append, r, p, n)			\
  ({									\
+	__label__ zabha, end;						\
+									\
+	if (IS_ENABLED(CONFIG_RISCV_ISA_ZABHA)) {			\
+		asm goto(ALTERNATIVE("nop", "j %[zabha]", 0,		\
+				     RISCV_ISA_EXT_ZABHA, 1)		\
+			 : : : : zabha);				\
+	}								\
+									\
  	u32 *__ptr32b = (u32 *)((ulong)(p) & ~0x3);			\
  	ulong __s = ((ulong)(p) & (0x4 - sizeof(*p))) * BITS_PER_BYTE;	\
  	ulong __mask = GENMASK(((sizeof(*p)) * BITS_PER_BYTE) - 1, 0)	\
@@ -28,12 +37,25 @@
  	       "	or   %1, %1, %z3\n"				\
  	       "	sc.w" sc_sfx " %1, %1, %2\n"			\
  	       "	bnez %1, 0b\n"					\
-	       append							\
+	       sc_append							\
  	       : "=&r" (__retx), "=&r" (__rc), "+A" (*(__ptr32b))	\
  	       : "rJ" (__newx), "rJ" (~__mask)				\
  	       : "memory");						\
  									\
  	r = (__typeof__(*(p)))((__retx & __mask) >> __s);		\
+	goto end;							\
+									\
+zabha:									\
+	if (IS_ENABLED(CONFIG_RISCV_ISA_ZABHA)) {			\
+		__asm__ __volatile__ (					\
+			prepend						\
+			"	amoswap" swap_sfx " %0, %z2, %1\n"	\
+			swap_append						\
+			: "=&r" (r), "+A" (*(p))			\
+			: "rJ" (n)					\
+			: "memory");					\
+	}								\
+end:;									\
  })
As for patch #1: why the semicolon? and should the second IS_ENABLED()
be kept?


diff --git a/arch/riscv/include/asm/hwcap.h b/arch/riscv/include/asm/hwcap.h
index e17d0078a651..f71ddd2ca163 100644
--- a/arch/riscv/include/asm/hwcap.h
+++ b/arch/riscv/include/asm/hwcap.h
@@ -81,6 +81,7 @@
  #define RISCV_ISA_EXT_ZTSO		72
  #define RISCV_ISA_EXT_ZACAS		73
  #define RISCV_ISA_EXT_XANDESPMU		74
+#define RISCV_ISA_EXT_ZABHA		75
#define RISCV_ISA_EXT_XLINUXENVCFG 127 diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
index 5ef48cb20ee1..c125d82c894b 100644
--- a/arch/riscv/kernel/cpufeature.c
+++ b/arch/riscv/kernel/cpufeature.c
@@ -257,6 +257,7 @@ const struct riscv_isa_ext_data riscv_isa_ext[] = {
  	__RISCV_ISA_EXT_DATA(zihintpause, RISCV_ISA_EXT_ZIHINTPAUSE),
  	__RISCV_ISA_EXT_DATA(zihpm, RISCV_ISA_EXT_ZIHPM),
  	__RISCV_ISA_EXT_DATA(zacas, RISCV_ISA_EXT_ZACAS),
+	__RISCV_ISA_EXT_DATA(zabha, RISCV_ISA_EXT_ZABHA),
  	__RISCV_ISA_EXT_DATA(zfa, RISCV_ISA_EXT_ZFA),
  	__RISCV_ISA_EXT_DATA(zfh, RISCV_ISA_EXT_ZFH),
  	__RISCV_ISA_EXT_DATA(zfhmin, RISCV_ISA_EXT_ZFHMIN),
To be squashed into patch #3?


Yep, done, thanks.



   Andrea

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