linux-kernel - [PATCH 1/2] tools: Add riscv barrier implementation

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Message-Id: <20240729-optimize_ring_buffer_read_riscv-v1-1-6bbc0f2434ee@rivosinc.com>
Date: Mon, 29 Jul 2024 13:50:35 -0700
From: Charlie Jenkins <charlie@...osinc.com>
To: Paul Walmsley <paul.walmsley@...ive.com>, 
 Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>, 
 Andrea Parri <parri.andrea@...il.com>
Cc: linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org, 
 Charlie Jenkins <charlie@...osinc.com>
Subject: [PATCH 1/2] tools: Add riscv barrier implementation

Many of the other architectures use their custom barrier implmentations.
Use the barrier code from the kernel sources to optimize barriers in
tools.

Signed-off-by: Charlie Jenkins <charlie@...osinc.com>
---
 tools/arch/riscv/include/asm/barrier.h | 39 ++++++++++++++++++++++++++++++++++
 tools/arch/riscv/include/asm/fence.h   | 13 ++++++++++++
 tools/include/asm/barrier.h            |  2 ++
 3 files changed, 54 insertions(+)

diff --git a/tools/arch/riscv/include/asm/barrier.h b/tools/arch/riscv/include/asm/barrier.h
new file mode 100644
index 000000000000..6997f197086d
--- /dev/null
+++ b/tools/arch/riscv/include/asm/barrier.h
@@ -0,0 +1,39 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copied from the kernel sources to tools/arch/riscv:
+ *
+ * Copyright (C) 2012 ARM Ltd.
+ * Copyright (C) 2013 Regents of the University of California
+ * Copyright (C) 2017 SiFive
+ */
+
+#ifndef _TOOLS_LINUX_ASM_RISCV_BARRIER_H
+#define _TOOLS_LINUX_ASM_RISCV_BARRIER_H
+
+#include <asm/fence.h>
+#include <linux/compiler.h>
+
+/* These barriers need to enforce ordering on both devices and memory. */
+#define mb()		RISCV_FENCE(iorw, iorw)
+#define rmb()		RISCV_FENCE(ir, ir)
+#define wmb()		RISCV_FENCE(ow, ow)
+
+/* These barriers do not need to enforce ordering on devices, just memory. */
+#define smp_mb()	RISCV_FENCE(rw, rw)
+#define smp_rmb()	RISCV_FENCE(r, r)
+#define smp_wmb()	RISCV_FENCE(w, w)
+
+#define smp_store_release(p, v)						\
+do {									\
+	RISCV_FENCE(rw, w);						\
+	WRITE_ONCE(*p, v);						\
+} while (0)
+
+#define smp_load_acquire(p)						\
+({									\
+	typeof(*p) ___p1 = READ_ONCE(*p);				\
+	RISCV_FENCE(r, rw);						\
+	___p1;								\
+})
+
+#endif /* _TOOLS_LINUX_ASM_RISCV_BARRIER_H */
diff --git a/tools/arch/riscv/include/asm/fence.h b/tools/arch/riscv/include/asm/fence.h
new file mode 100644
index 000000000000..37860e86771d
--- /dev/null
+++ b/tools/arch/riscv/include/asm/fence.h
@@ -0,0 +1,13 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copied from the kernel sources to tools/arch/riscv:
+ */
+
+#ifndef _ASM_RISCV_FENCE_H
+#define _ASM_RISCV_FENCE_H
+
+#define RISCV_FENCE_ASM(p, s)		"\tfence " #p "," #s "\n"
+#define RISCV_FENCE(p, s) \
+	({ __asm__ __volatile__ (RISCV_FENCE_ASM(p, s) : : : "memory"); })
+
+#endif	/* _ASM_RISCV_FENCE_H */
diff --git a/tools/include/asm/barrier.h b/tools/include/asm/barrier.h
index 8d378c57cb01..0c21678ac5e6 100644
--- a/tools/include/asm/barrier.h
+++ b/tools/include/asm/barrier.h
@@ -8,6 +8,8 @@
 #include "../../arch/arm64/include/asm/barrier.h"
 #elif defined(__powerpc__)
 #include "../../arch/powerpc/include/asm/barrier.h"
+#elif defined(__riscv)
+#include "../../arch/riscv/include/asm/barrier.h"
 #elif defined(__s390__)
 #include "../../arch/s390/include/asm/barrier.h"
 #elif defined(__sh__)

-- 
2.44.0