[PATCH v2 01/11] lib: sbi: Fix sbi_hart_switch_mode() for u-mode

[Anup Patel]

> -----Original Message-----
> From: Anup Patel <Anup.Patel at wdc.com>
> Sent: 04 December 2020 21:22
> To: Atish Patra <Atish.Patra at wdc.com>; Alistair Francis
> <Alistair.Francis at wdc.com>
> Cc: Anup Patel <anup at brainfault.org>; opensbi at lists.infradead.org; Anup
> Patel <Anup.Patel at wdc.com>; Alistair Francis <Alistair.Francis at wdc.com>
> Subject: [PATCH v2 01/11] lib: sbi: Fix sbi_hart_switch_mode() for u-mode
> 
> We should check and access N-extension CSRs in sbi_hart_switch_mode()
> when next_mode is u-mode because N-extension is optional.
> 
> Signed-off-by: Anup Patel <anup.patel at wdc.com>
> Reviewed-by: Alistair Francis <alistair.francis at wdc.com>
> Reviewed-by: Atish Patra <atish.patra at wdc.com>
> ---
>  lib/sbi/sbi_hart.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/lib/sbi/sbi_hart.c b/lib/sbi/sbi_hart.c index 30d8aef..fc86e9f
> 100644
> --- a/lib/sbi/sbi_hart.c
> +++ b/lib/sbi/sbi_hart.c
> @@ -522,9 +522,11 @@ sbi_hart_switch_mode(unsigned long arg0,
> unsigned long arg1,
>  		csr_write(CSR_SIE, 0);
>  		csr_write(CSR_SATP, 0);
>  	} else if (next_mode == PRV_U) {
> -		csr_write(CSR_UTVEC, next_addr);
> -		csr_write(CSR_USCRATCH, 0);
> -		csr_write(CSR_UIE, 0);
> +		if (misa_extension('N')) {
> +			csr_write(CSR_UTVEC, next_addr);
> +			csr_write(CSR_USCRATCH, 0);
> +			csr_write(CSR_UIE, 0);
> +		}
>  	}
> 
>  	register unsigned long a0 asm("a0") = arg0;
> --
> 2.25.1

Applied this patch to the riscv/opensbi repo.

Regards,
Anup