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

From: Palmer Dabbelt <palmer@dabbelt.com>
To: andy.chiu@sifive.com
Cc: linux-riscv@lists.infradead.org, anup@brainfault.org,
	atishp@atishpatra.org, kvm-riscv@lists.infradead.org,
	kvm@vger.kernel.org, Vineet Gupta <vineetg@rivosinc.com>,
	greentime.hu@sifive.com, guoren@linux.alibaba.com,
	vincent.chen@sifive.com, hankuan.chen@sifive.com,
	andy.chiu@sifive.com, Paul Walmsley <paul.walmsley@sifive.com>,
	aou@eecs.berkeley.edu, guoren@kernel.org, nsaenzju@redhat.com,
	jszhang@kernel.org, Bjorn Topel <bjorn@rivosinc.com>,
	frederic@kernel.org, abrestic@rivosinc.com,
	heiko.stuebner@vrull.eu, alex@ghiti.fr, masahiroy@kernel.org
Subject: Re: [PATCH -next v19 06/24] riscv: Disable Vector Instructions for kernel itself
Date: Thu, 11 May 2023 15:56:39 -0700 (PDT)	[thread overview]
Message-ID: <mhng-6d02bea7-ef2c-4840-96e3-912bfac4ffc4@palmer-ri-x1c9a> (raw)
In-Reply-To: <20230509103033.11285-7-andy.chiu@sifive.com>

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>