linux-kernel - [PATCH v3 06/11] riscv: Implement xchg8/16() using Zabha

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Message-Id: <20240717061957.140712-7-alexghiti@rivosinc.com>
Date: Wed, 17 Jul 2024 08:19:52 +0200
From: Alexandre Ghiti <alexghiti@...osinc.com>
To: Jonathan Corbet <corbet@....net>,
	Paul Walmsley <paul.walmsley@...ive.com>,
	Palmer Dabbelt <palmer@...belt.com>,
	Albert Ou <aou@...s.berkeley.edu>,
	Conor Dooley <conor@...nel.org>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Andrea Parri <parri.andrea@...il.com>,
	Nathan Chancellor <nathan@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Will Deacon <will@...nel.org>,
	Waiman Long <longman@...hat.com>,
	Boqun Feng <boqun.feng@...il.com>,
	Arnd Bergmann <arnd@...db.de>,
	Leonardo Bras <leobras@...hat.com>,
	Guo Ren <guoren@...nel.org>,
	linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-riscv@...ts.infradead.org,
	linux-arch@...r.kernel.org
Cc: Alexandre Ghiti <alexghiti@...osinc.com>
Subject: [PATCH v3 06/11] riscv: Implement xchg8/16() using Zabha

This adds runtime support for Zabha in xchg8/16() operations.

Signed-off-by: Alexandre Ghiti <alexghiti@...osinc.com>
---
 arch/riscv/include/asm/cmpxchg.h | 32 +++++++++++++++++++++++++++++---
 1 file changed, 29 insertions(+), 3 deletions(-)

diff --git a/arch/riscv/include/asm/cmpxchg.h b/arch/riscv/include/asm/cmpxchg.h
index 608d98522557..091e6612ddb3 100644
--- a/arch/riscv/include/asm/cmpxchg.h
+++ b/arch/riscv/include/asm/cmpxchg.h
@@ -11,8 +11,27 @@
 #include <asm/fence.h>
 #include <asm/alternative.h>
 
-#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__ no_zabha, end;					\
+									\
+	if (IS_ENABLED(CONFIG_RISCV_ISA_ZABHA)) {			\
+		asm goto(ALTERNATIVE("j %[no_zabha]", "nop", 0,		\
+				     RISCV_ISA_EXT_ZABHA, 1)		\
+			 : : : : no_zabha);				\
+									\
+		__asm__ __volatile__ (					\
+			prepend						\
+			"	amoswap" swap_sfx " %0, %z2, %1\n"	\
+			swap_append					\
+			: "=&r" (r), "+A" (*(p))			\
+			: "rJ" (n)					\
+			: "memory");					\
+		goto end;						\
+	}								\
+									\
+no_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 +47,14 @@
 	       "	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);		\
+									\
+end:;									\
 })
 
 #define __arch_xchg(sfx, prepend, append, r, p, n)			\
@@ -56,8 +77,13 @@
 									\
 	switch (sizeof(*__ptr)) {					\
 	case 1:								\
+		__arch_xchg_masked(sc_sfx, ".b" swap_sfx,		\
+				   prepend, sc_append, swap_append,	\
+				   __ret, __ptr, __new);		\
+		break;							\
 	case 2:								\
-		__arch_xchg_masked(sc_sfx, prepend, sc_append,		\
+		__arch_xchg_masked(sc_sfx, ".h" swap_sfx,		\
+				   prepend, sc_append, swap_append,	\
 				   __ret, __ptr, __new);		\
 		break;							\
 	case 4:								\
-- 
2.39.2