linux-kernel - [PATCH v2] RISC-V: Enable cbo.clean/flush in usermode

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Message-Id: <20241224123946.97486-1-cuiyunhui@bytedance.com>
Date: Tue, 24 Dec 2024 20:39:46 +0800
From: Yunhui Cui <cuiyunhui@...edance.com>
To: paul.walmsley@...ive.com,
	palmer@...belt.com,
	aou@...s.berkeley.edu,
	conor@...nel.org,
	charlie@...osinc.com,
	ajones@...tanamicro.com,
	samuel.holland@...ive.com,
	cleger@...osinc.com,
	andybnac@...il.com,
	alexghiti@...osinc.com,
	linux-riscv@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Cc: Yunhui Cui <cuiyunhui@...edance.com>
Subject: [PATCH v2] RISC-V: Enable cbo.clean/flush in usermode

Enabling cbo.clean and cbo.flush in user mode makes it more
convenient to manage the cache state and achieve better performance.

Signed-off-by: Yunhui Cui <cuiyunhui@...edance.com>
---
 arch/riscv/kernel/cpufeature.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
index c0916ed318c2..60d180b98f52 100644
--- a/arch/riscv/kernel/cpufeature.c
+++ b/arch/riscv/kernel/cpufeature.c
@@ -30,6 +30,7 @@
 #define NUM_ALPHA_EXTS ('z' - 'a' + 1)
 
 static bool any_cpu_has_zicboz;
+static bool any_cpu_has_zicbom;
 
 unsigned long elf_hwcap __read_mostly;
 
@@ -87,6 +88,8 @@ static int riscv_ext_zicbom_validate(const struct riscv_isa_ext_data *data,
 		pr_err("Zicbom disabled as cbom-block-size present, but is not a power-of-2\n");
 		return -EINVAL;
 	}
+
+	any_cpu_has_zicbom = true;
 	return 0;
 }
 
@@ -944,6 +947,11 @@ void __init riscv_user_isa_enable(void)
 		current->thread.envcfg |= ENVCFG_CBZE;
 	else if (any_cpu_has_zicboz)
 		pr_warn("Zicboz disabled as it is unavailable on some harts\n");
+
+	if (riscv_has_extension_unlikely(RISCV_ISA_EXT_ZICBOM))
+		current->thread.envcfg |= ENVCFG_CBCFE;
+	else if (any_cpu_has_zicbom)
+		pr_warn("Zicbom disabled as it is unavailable on some harts\n");
 }
 
 #ifdef CONFIG_RISCV_ALTERNATIVE
-- 
2.39.2