Re: [PATCH -next v19 06/24] riscv: Disable Vector Instructions for kernel itself

Palmer Dabbelt
2023-05-12T00:01:23Z

On Tue, 09 May 2023 03:30:15 PDT (-0700), andy.chiu@sifive.com wrote:
> From: Guo Ren <guoren@linux.alibaba.com>
>
> Disable vector instructions execution for kernel mode at its entrances.
> This helps find illegal uses of vector in the kernel space, which is
> similar to the fpu.
>
> 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>
> Signed-off-by: Vineet Gupta <vineetg@rivosinc.com>
> Signed-off-by: Andy Chiu <andy.chiu@sifive.com>
> Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
> Reviewed-by: Heiko Stuebner <heiko.stuebner@vrull.eu>
> Tested-by: Heiko Stuebner <heiko.stuebner@vrull.eu>
> ---
> Changelog V19:
> - Add description in commit msg (Heiko's suggestion on v17)
>
> arch/riscv/kernel/entry.S | 6 +++---
> arch/riscv/kernel/head.S | 12 ++++++------
> 2 files changed, 9 insertions(+), 9 deletions(-)
>
> diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S
> index 3fbb100bc9e4..e9ae284a55c1 100644
> --- a/arch/riscv/kernel/entry.S
> +++ b/arch/riscv/kernel/entry.S
> @@ -48,10 +48,10 @@ _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_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 3fd6a4bd9c3e..e16bb2185d55 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_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_VS
> csrc CSR_STATUS, t0
>
> #ifdef CONFIG_RISCV_BOOT_SPINWAIT

Reviewed-by: Palmer Dabbelt <palmer@rivosinc.com>