linux-kernel - [PATCH v3 3/4] riscv: Add ARCH_HAS

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Message-Id: <20250421142441.395849-4-alexghiti@rivosinc.com>
Date: Mon, 21 Apr 2025 16:24:40 +0200
From: Alexandre Ghiti <alexghiti@...osinc.com>
To: Paul Walmsley <paul.walmsley@...ive.com>,
	Palmer Dabbelt <palmer@...belt.com>,
	Alexandre Ghiti <alex@...ti.fr>,
	linux-riscv@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Cc: Guo Ren <guoren@...ux.alibaba.com>,
	Guo Ren <guoren@...nel.org>,
	Alexandre Ghiti <alexghiti@...osinc.com>
Subject: [PATCH v3 3/4] riscv: Add ARCH_HAS_PREFETCH[W] support with Zicbop

From: Guo Ren <guoren@...ux.alibaba.com>

Enable Linux prefetch and prefetchw primitives using Zicbop.

Signed-off-by: Guo Ren <guoren@...ux.alibaba.com>
Signed-off-by: Guo Ren <guoren@...nel.org>
Link: https://lore.kernel.org/r/20231231082955.16516-3-guoren@kernel.org
Signed-off-by: Alexandre Ghiti <alexghiti@...osinc.com>
---
 arch/riscv/include/asm/processor.h | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/arch/riscv/include/asm/processor.h b/arch/riscv/include/asm/processor.h
index 09d4c963399a..39dfab495a4c 100644
--- a/arch/riscv/include/asm/processor.h
+++ b/arch/riscv/include/asm/processor.h
@@ -13,6 +13,9 @@
 #include <vdso/processor.h>
 
 #include <asm/ptrace.h>
+#include <asm/insn-def.h>
+#include <asm/alternative-macros.h>
+#include <asm/hwcap.h>
 
 #define arch_get_mmap_end(addr, len, flags)			\
 ({								\
@@ -135,6 +138,27 @@ static inline void arch_thread_struct_whitelist(unsigned long *offset,
 #define KSTK_EIP(tsk)		(task_pt_regs(tsk)->epc)
 #define KSTK_ESP(tsk)		(task_pt_regs(tsk)->sp)
 
+#define PREFETCH_ASM(x)							\
+	ALTERNATIVE(__nops(1), PREFETCH_R(x, 0), 0,			\
+		    RISCV_ISA_EXT_ZICBOP, CONFIG_RISCV_ISA_ZICBOP)
+
+#define PREFETCHW_ASM(x)						\
+	ALTERNATIVE(__nops(1), PREFETCH_W(x, 0), 0,			\
+		    RISCV_ISA_EXT_ZICBOP, CONFIG_RISCV_ISA_ZICBOP)
+
+#ifdef CONFIG_RISCV_ISA_ZICBOP
+#define ARCH_HAS_PREFETCH
+static inline void prefetch(const void *x)
+{
+	__asm__ __volatile__(PREFETCH_ASM(%0) : : "r" (x) : "memory");
+}
+
+#define ARCH_HAS_PREFETCHW
+static inline void prefetchw(const void *x)
+{
+	__asm__ __volatile__(PREFETCHW_ASM(%0) : : "r" (x) : "memory");
+}
+#endif /* CONFIG_RISCV_ISA_ZICBOP */
 
 /* Do necessary setup to start up a newly executed thread. */
 extern void start_thread(struct pt_regs *regs,
-- 
2.39.2