linux-kernel - [PATCH v9 16/17] riscv: Fix an illegal instruction exception when accessing vlenb without enable vector first

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Message-Id: <3c0297d8335e4cac54a4397c880092c1c983e04e.1636362169.git.greentime.hu@sifive.com>
Date:   Tue,  9 Nov 2021 17:48:28 +0800
From:   Greentime Hu <greentime.hu@...ive.com>
To:     palmer@...belt.com, paul.walmsley@...ive.com,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        aou@...s.berkeley.edu
Subject: [PATCH v9 16/17] riscv: Fix an illegal instruction exception when accessing vlenb without enable vector first

It triggered an illegal instruction exception when accessing vlenb CSR
without enable vector first. To fix this issue, we should enable vector
before using it and disable vector after using it.

Co-developed-by: Vincent Chen <vincent.chen@...ive.com>
Signed-off-by: Vincent Chen <vincent.chen@...ive.com>
Signed-off-by: Greentime Hu <greentime.hu@...ive.com>
---
 arch/riscv/include/asm/vector.h        | 2 ++
 arch/riscv/kernel/cpufeature.c         | 2 ++
 arch/riscv/kernel/kernel_mode_vector.c | 6 ++++--
 3 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/arch/riscv/include/asm/vector.h b/arch/riscv/include/asm/vector.h
index 5d7f14453f68..ca063c8f47f2 100644
--- a/arch/riscv/include/asm/vector.h
+++ b/arch/riscv/include/asm/vector.h
@@ -8,6 +8,8 @@
 
 #include <linux/types.h>
 
+void rvv_enable(void);
+void rvv_disable(void);
 void kernel_rvv_begin(void);
 void kernel_rvv_end(void);
 
diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
index 8e7557980faf..0139ec20adce 100644
--- a/arch/riscv/kernel/cpufeature.c
+++ b/arch/riscv/kernel/cpufeature.c
@@ -159,7 +159,9 @@ void __init riscv_fill_hwcap(void)
 	if (elf_hwcap & COMPAT_HWCAP_ISA_V) {
 		static_branch_enable(&cpu_hwcap_vector);
 		/* There are 32 vector registers with vlenb length. */
+		rvv_enable();
 		riscv_vsize = csr_read(CSR_VLENB) * 32;
+		rvv_disable();
 	}
 #endif
 }
diff --git a/arch/riscv/kernel/kernel_mode_vector.c b/arch/riscv/kernel/kernel_mode_vector.c
index 8d2e53ea25c1..1ecb6ec5c56d 100644
--- a/arch/riscv/kernel/kernel_mode_vector.c
+++ b/arch/riscv/kernel/kernel_mode_vector.c
@@ -71,15 +71,17 @@ static void put_cpu_vector_context(void)
 	preempt_enable();
 }
 
-static void rvv_enable(void)
+void rvv_enable(void)
 {
 	csr_set(CSR_STATUS, SR_VS);
 }
+EXPORT_SYMBOL(rvv_enable);
 
-static void rvv_disable(void)
+void rvv_disable(void)
 {
 	csr_clear(CSR_STATUS, SR_VS);
 }
+EXPORT_SYMBOL(rvv_disable);
 
 /*
  * kernel_rvv_begin(): obtain the CPU vector registers for use by the calling
-- 
2.31.1