linux-kernel - [PATCH v9 07/17] riscv: Reset vector register

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Message-Id: <8612e69a10235e67fac8a55864e77a4ab8f771ac.1636362169.git.greentime.hu@sifive.com>
Date:   Tue,  9 Nov 2021 17:48:19 +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 07/17] riscv: Reset vector register

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

Reset vector registers at boot-time and disable vector instructions
execution for kernel mode.

Signed-off-by: Guo Ren <guoren@...ux.alibaba.com>
Co-developed-by: Vincent Chen <vincent.chen@...ive.com>
Signed-off-by: Vincent Chen <vincent.chen@...ive.com>
Co-developed-by: Han-Kuan Chen <hankuan.chen@...ive.com>
Signed-off-by: Han-Kuan Chen <hankuan.chen@...ive.com>
Co-developed-by: Greentime Hu <greentime.hu@...ive.com>
Signed-off-by: Greentime Hu <greentime.hu@...ive.com>
---
 arch/riscv/kernel/entry.S |  6 +++---
 arch/riscv/kernel/head.S  | 22 ++++++++++++++++++++--
 2 files changed, 23 insertions(+), 5 deletions(-)

diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S
index 98f502654edd..ad0fa80ada81 100644
--- a/arch/riscv/kernel/entry.S
+++ b/arch/riscv/kernel/entry.S
@@ -77,10 +77,10 @@ _save_context:
 	 * Disable user-mode memory access as it should only be set in the
 	 * actual user copy routines.
 	 *
-	 * Disable the FPU to detect illegal usage of floating point in kernel
-	 * space.
+	 * Disable the FPU/Vector to detect illegal usage of floating point
+	 * or vector in kernel space.
 	 */
-	li t0, SR_SUM | SR_FS
+	li t0, SR_SUM | SR_FS | SR_VS
 
 	REG_L s0, TASK_TI_USER_SP(tp)
 	csrrc s1, CSR_STATUS, t0
diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
index 52c5ff9804c5..551afe1de85e 100644
--- a/arch/riscv/kernel/head.S
+++ b/arch/riscv/kernel/head.S
@@ -242,10 +242,10 @@ pmp_done:
 .option pop
 
 	/*
-	 * Disable FPU to detect illegal usage of
+	 * Disable FPU & VECTOR to detect illegal usage of
 	 * floating point in kernel space
 	 */
-	li t0, SR_FS
+	li t0, SR_FS | SR_VS
 	csrc CSR_STATUS, t0
 
 #ifdef CONFIG_SMP
@@ -433,6 +433,24 @@ ENTRY(reset_regs)
 	csrw	fcsr, 0
 	/* note that the caller must clear SR_FS */
 #endif /* CONFIG_FPU */
+
+#ifdef CONFIG_VECTOR
+	csrr	t0, CSR_MISA
+	li	t1, (COMPAT_HWCAP_ISA_V >> 16)
+	slli	t1, t1, 16
+	and	t0, t0, t1
+	beqz	t0, .Lreset_regs_done
+
+	li	t1, SR_VS
+	csrs	CSR_STATUS, t1
+	vsetvli t1, x0, e8, m8
+	vmv.v.i v0, 0
+	vmv.v.i v8, 0
+	vmv.v.i v16, 0
+	vmv.v.i v24, 0
+	/* note that the caller must clear SR_VS */
+#endif /* CONFIG_VECTOR */
+
 .Lreset_regs_done:
 	ret
 END(reset_regs)
-- 
2.31.1