linux-kernel - [PATCH v3 02/29] riscv: define default value for envcfg for task

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Message-ID: <20240403234054.2020347-3-debug@rivosinc.com>
Date: Wed,  3 Apr 2024 16:34:50 -0700
From: Deepak Gupta <debug@...osinc.com>
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Subject: [PATCH v3 02/29] riscv: define default value for envcfg for task

Defines a base default value for envcfg per task. By default all tasks
should have cache zeroing capability. Any future base capabilities that
apply to all tasks can be turned on same way.

Signed-off-by: Deepak Gupta <debug@...osinc.com>
---
 arch/riscv/include/asm/csr.h | 2 ++
 arch/riscv/kernel/process.c  | 6 ++++++
 2 files changed, 8 insertions(+)

diff --git a/arch/riscv/include/asm/csr.h b/arch/riscv/include/asm/csr.h
index 2468c55933cd..bbd2207adb39 100644
--- a/arch/riscv/include/asm/csr.h
+++ b/arch/riscv/include/asm/csr.h
@@ -202,6 +202,8 @@
 #define ENVCFG_CBIE_FLUSH		_AC(0x1, UL)
 #define ENVCFG_CBIE_INV			_AC(0x3, UL)
 #define ENVCFG_FIOM			_AC(0x1, UL)
+/* by default all threads should be able to zero cache */
+#define ENVCFG_BASE			ENVCFG_CBZE
 
 /* Smstateen bits */
 #define SMSTATEEN0_AIA_IMSIC_SHIFT	58
diff --git a/arch/riscv/kernel/process.c b/arch/riscv/kernel/process.c
index 92922dbd5b5c..d3109557f951 100644
--- a/arch/riscv/kernel/process.c
+++ b/arch/riscv/kernel/process.c
@@ -152,6 +152,12 @@ void start_thread(struct pt_regs *regs, unsigned long pc,
 	else
 		regs->status |= SR_UXL_64;
 #endif
+	/*
+	 * read current envcfg settings, AND it with base settings applicable
+	 * for all the tasks. Base settings should've been set up during CPU
+	 * bring up.
+	 */
+	current->thread_info.envcfg = csr_read(CSR_ENVCFG) & ENVCFG_BASE;
 }
 
 void flush_thread(void)
-- 
2.43.2