Re: [PATCH -next v13 05/19] riscv: Disable Vector Instructions for kernel itself

From: Conor Dooley <conor@kernel.org>
To: Andy Chiu <andy.chiu@sifive.com>
Cc: linux-riscv@lists.infradead.org, palmer@dabbelt.com,
	anup@brainfault.org, atishp@atishpatra.org,
	kvm-riscv@lists.infradead.org, kvm@vger.kernel.org,
	vineetg@rivosinc.com, greentime.hu@sifive.com,
	guoren@linux.alibaba.com, Vincent Chen <vincent.chen@sifive.com>,
	Han-Kuan Chen <hankuan.chen@sifive.com>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Albert Ou <aou@eecs.berkeley.edu>, Guo Ren <guoren@kernel.org>,
	Nicolas Saenz Julienne <nsaenzju@redhat.com>,
	Frederic Weisbecker <frederic@kernel.org>,
	Andrew Bresticker <abrestic@rivosinc.com>,
	Jisheng Zhang <jszhang@kernel.org>,
	Changbin Du <changbin.du@intel.com>, Myrtle Shah <gatecat@ds0.me>
Subject: Re: [PATCH -next v13 05/19] riscv: Disable Vector Instructions for kernel itself
Date: Wed, 25 Jan 2023 21:51:02 +0000	[thread overview]
Message-ID: <Y9GkRltyP4bTCAkQ@spud> (raw)
In-Reply-To: <20230125142056.18356-6-andy.chiu@sifive.com>

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On Wed, Jan 25, 2023 at 02:20:42PM +0000, Andy Chiu wrote:
> Disable vector instructions execution for kernel mode at its entrances.
> 
> 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>
> [vineetg: split off vecreg file clearing]
> Signed-off-by: Andy Chiu <andy.chiu@sifive.com>

That's a hilarious co-developed-by list for adding "| foo".
I can only assume that this is mostly related to the asm that was
removed by Vineet?

Either way:
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>

> ---
>  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 99d38fdf8b18..e38676d9a0d6 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_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 ea803c96eeff..7cc975ce619d 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
> -- 
> 2.17.1
> 

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