[PATCH v2 5/9] lib: sbi_hart: add WID protection mechanism

[Radim Krcmar]

2026-10-16T17:24:07+00:00, Radim Krcmar <rkrcmar at qti.qualcomm.com>:
> 2026-08-17T17:04:59+08:00, Yu-Chien Peter Lin <peter.lin at sifive.com>:
>> +static struct sbi_hart_protection wid_protection = {
>> +	.name		= "wid",
>> +	.rating		= 100,
>> +	.type		= SBI_HART_PROTECTION_TYPE_ID,
>> +	.configure	= sbi_hart_worlds_configure,
>> +	.unconfigure	= NULL
>> +};
>> +
>> +int sbi_hart_worlds_init(struct sbi_scratch *scratch)
>> +{
>> +	if (!sbi_hart_has_extension(scratch, SBI_HART_EXT_SMLWID))
>> +		return 0;
>> +
>> +	return sbi_hart_protection_register(&wid_protection);
>
> All that I said above applies to domain intialization.
> The actual code during context switch should be much simpler:
>
>   {
>     csr_write(CSR_MLWID, dom->wid);
>     if (sbi_hart_has_extension(scratch, SBI_HART_EXT_SMWIDDELEG))
>       csr_write(CSR_MWIDDELEG, dom->widdeleg);
>   }
>
> Or only
>
>   {
>     csr_write(CSR_MLWID, dom->wid);
>   }
>
> since we have to touch mwiddeleg when switching slwid anyway and the
> unconfigure/configure is not good.
> Alternatively, we can add a `switch` function to sbi_hart_protection and
> move the slwid switching here.

Taking a step back, what is actually the benefit of fitting WID into
sbi_hart_protection instead of simple domain state?

Thanks.