[RFC 3/3] lib: sbi: enable seed access in S-mode

[Xiang W]

在 2023-10-29星期日的 00:49 +0200，Heinrich Schuchardt写道：
> If ISA extension Zkr is available, set
> 
>     mseccfg.sseed=1
>     mseccfg.useed=0
> 
> This enables access to the seed CSR in S-mode but not in U-mode.
> 
> Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt at canonical.com>
> ---
>  lib/sbi/sbi_hart.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/lib/sbi/sbi_hart.c b/lib/sbi/sbi_hart.c
> index 569596f..5a3e8ee 100644
> --- a/lib/sbi/sbi_hart.c
> +++ b/lib/sbi/sbi_hart.c
> @@ -530,6 +530,15 @@ int sbi_hart_unmap_saddr(void)
>  	return pmp_disable(SBI_SMEPMP_RESV_ENTRY);
>  }
>  
> +static void sbi_hart_zkr_configure(struct sbi_scratch *scratch)
> +{
> +	unsigned long mseccfg_val = csr_read(CSR_MSECCFG);
> +
> +	mseccfg_val |= MSECCFG_SSEED;
> +	mseccfg_val &= ~MSECCFG_USEED;
> +	csr_set(CSR_MSECCFG, mseccfg_val);
> +}
> +
>  int sbi_hart_pmp_configure(struct sbi_scratch *scratch)
>  {
>  	int rc;
> @@ -551,6 +560,9 @@ int sbi_hart_pmp_configure(struct sbi_scratch *scratch)
>  		rc = sbi_hart_oldpmp_configure(scratch, pmp_count,
>  						pmp_gran_log2, pmp_addr_max);
>  
> +	if (sbi_hart_has_extension(scratch, SBI_HART_EXT_ZKR))
> +		sbi_hart_zkr_configure(scratch);
> +
What is the relationship between zkr and pmp? Maybe it's better to move 
into sbi_hart_reinit.

Regards,
Xiang W
>  	/*
>  	 * As per section 3.7.2 of privileged specification v1.12,
>  	 * virtual address translations can be speculatively performed
> -- 
> 2.40.1
> 
>