linux-kernel - [PATCH v5 07/12] tools: riscv: Add header file vdso/processor.h

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Message-Id: <212d0d848e54c887944ec38bd9f9729df8d1a27f.1705916069.git.haibo1.xu@intel.com>
Date: Mon, 22 Jan 2024 17:58:37 +0800
From: Haibo Xu <haibo1.xu@...el.com>
To: 
Cc: xiaobo55x@...il.com,
	ajones@...tanamicro.com,
	Haibo Xu <haibo1.xu@...el.com>,
	Paul Walmsley <paul.walmsley@...ive.com>,
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	Maciej Wieczor-Retman <maciej.wieczor-retman@...el.com>,
	linux-kernel@...r.kernel.org,
	linux-riscv@...ts.infradead.org,
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Subject: [PATCH v5 07/12] tools: riscv: Add header file vdso/processor.h

Borrow the cpu_relax() definitions from kernel's
arch/riscv/include/asm/vdso/processor.h to tools/ for riscv.

Signed-off-by: Haibo Xu <haibo1.xu@...el.com>
Reviewed-by: Andrew Jones <ajones@...tanamicro.com>
---
 tools/arch/riscv/include/asm/vdso/processor.h | 32 +++++++++++++++++++
 1 file changed, 32 insertions(+)
 create mode 100644 tools/arch/riscv/include/asm/vdso/processor.h

diff --git a/tools/arch/riscv/include/asm/vdso/processor.h b/tools/arch/riscv/include/asm/vdso/processor.h
new file mode 100644
index 000000000000..662aca039848
--- /dev/null
+++ b/tools/arch/riscv/include/asm/vdso/processor.h
@@ -0,0 +1,32 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef __ASM_VDSO_PROCESSOR_H
+#define __ASM_VDSO_PROCESSOR_H
+
+#ifndef __ASSEMBLY__
+
+#include <asm-generic/barrier.h>
+
+static inline void cpu_relax(void)
+{
+#ifdef __riscv_muldiv
+	int dummy;
+	/* In lieu of a halt instruction, induce a long-latency stall. */
+	__asm__ __volatile__ ("div %0, %0, zero" : "=r" (dummy));
+#endif
+
+#ifdef CONFIG_TOOLCHAIN_HAS_ZIHINTPAUSE
+	/*
+	 * Reduce instruction retirement.
+	 * This assumes the PC changes.
+	 */
+	__asm__ __volatile__ ("pause");
+#else
+	/* Encoding of the pause instruction */
+	__asm__ __volatile__ (".4byte 0x100000F");
+#endif
+	barrier();
+}
+
+#endif /* __ASSEMBLY__ */
+
+#endif /* __ASM_VDSO_PROCESSOR_H */
-- 
2.34.1