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Subject[PATCH v12 06/17] riscv: Reset vector register
Date
From: Guo Ren <guoren@linux.alibaba.com>

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

Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
Co-developed-by: Vincent Chen <vincent.chen@sifive.com>
Signed-off-by: Vincent Chen <vincent.chen@sifive.com>
Co-developed-by: Han-Kuan Chen <hankuan.chen@sifive.com>
Signed-off-by: Han-Kuan Chen <hankuan.chen@sifive.com>
Co-developed-by: Greentime Hu <greentime.hu@sifive.com>
Signed-off-by: Greentime Hu <greentime.hu@sifive.com>
Reviewed-by: Palmer Dabbelt <palmer@rivosinc.com>
---
arch/riscv/kernel/entry.S | 6 +++---
arch/riscv/kernel/head.S | 35 +++++++++++++++++++++++++++++------
2 files changed, 32 insertions(+), 9 deletions(-)

diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S
index b9eda3fcbd6d..1e9987376591 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 b865046e4dbb..2c81ca42ec4e 100644
--- a/arch/riscv/kernel/head.S
+++ b/arch/riscv/kernel/head.S
@@ -140,10 +140,10 @@ secondary_start_sbi:
.option pop

/*
- * Disable FPU to detect illegal usage of
- * floating point in kernel space
+ * Disable FPU & VECTOR to detect illegal usage of
+ * floating point or vector in kernel space
*/
- li t0, SR_FS
+ li t0, SR_FS | SR_VS
csrc CSR_STATUS, t0

/* Set trap vector to spin forever to help debug */
@@ -234,10 +234,10 @@ pmp_done:
.option pop

/*
- * Disable FPU to detect illegal usage of
- * floating point in kernel space
+ * Disable FPU & VECTOR to detect illegal usage of
+ * floating point or vector in kernel space
*/
- li t0, SR_FS
+ li t0, SR_FS | SR_VS
csrc CSR_STATUS, t0

#ifdef CONFIG_RISCV_BOOT_SPINWAIT
@@ -431,6 +431,29 @@ 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
+ and t0, t0, t1
+ beqz t0, .Lreset_regs_done
+
+ /*
+ * Clear vector registers and reset vcsr
+ * VLMAX has a defined value, VLEN is a constant,
+ * and this form of vsetvli is defined to set vl to VLMAX.
+ */
+ li t1, SR_VS
+ csrs CSR_STATUS, t1
+ csrs CSR_VCSR, x0
+ vsetvli t1, x0, e8, m8, ta, ma
+ 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)
--
2.25.1
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