[RFC PATCH 3/4] lib: sbi: implement SBI_FWFT_DOUBLE_TRAP_ENABLE

[Clément Léger]

On 19/04/2024 00:31, Samuel Holland wrote:
> Hi Clément,
> 
> On 2024-04-18 8:54 AM, Clément Léger wrote:
>> Add support for double trap firmware feature
>>
>> Signed-off-by: Clément Léger <cleger at rivosinc.com>
>> ---
>>  lib/sbi/sbi_fwft.c | 53 +++++++++++++++++++++++++++++++++++++++++++++-
>>  1 file changed, 52 insertions(+), 1 deletion(-)
>>
>> diff --git a/lib/sbi/sbi_fwft.c b/lib/sbi/sbi_fwft.c
>> index 78fbd45..965d47a 100644
>> --- a/lib/sbi/sbi_fwft.c
>> +++ b/lib/sbi/sbi_fwft.c
>> @@ -34,7 +34,7 @@ static unsigned long fwft_ptr_offset;
>>  
>>  #define MIS_DELEG (1UL << CAUSE_MISALIGNED_LOAD | 1UL << CAUSE_MISALIGNED_STORE)
>>  
>> -#define SUPPORTED_FEATURE_COUNT	3
>> +#define SUPPORTED_FEATURE_COUNT	4
>>  
>>  struct fwft_config;
>>  
>> @@ -149,6 +149,51 @@ static int sbi_get_adue(struct fwft_config *conf, unsigned long *value)
>>  	return SBI_OK;
>>  }
>>  
>> +#if __riscv_xlen == 32
>> +# define CSR_MENVCFG_DBLTRP	CSR_MENVCFGH
>> +# define DBLTRP_DTE	(ENVCFG_DTE >> 32)
>> +#else
>> +# define CSR_MENVCFG_DBLTRP	CSR_MENVCFG
>> +# define DBLTRP_DTE	ENVCFG_DTE
>> +#endif
>> +
>> +static int sbi_double_trap_supported(struct fwft_config *conf)
>> +{
>> +	if (!sbi_hart_has_extension(sbi_scratch_thishart_ptr(),
>> +				    SBI_HART_EXT_SSDBLTRP))
>> +		return SBI_ENOTSUPP;
>> +
>> +	return SBI_OK;
>> +}
>> +
>> +static int sbi_set_double_trap_enable(struct fwft_config *conf,
>> +				      unsigned long value)
>> +{
>> +	struct sbi_scratch *scratch = sbi_scratch_thishart_ptr();
>> +
>> +	if (!sbi_hart_has_extension(scratch, SBI_HART_EXT_SSDBLTRP))
>> +		return SBI_ENOTSUPP;
>> +
>> +	if (value)
>> +		csr_set(CSR_MENVCFG_DBLTRP, DBLTRP_DTE);
>> +	else
>> +		csr_clear(CSR_MENVCFG_DBLTRP, DBLTRP_DTE);
> 
> This configuration will be lost after hart non-retentive suspend. Probably
> mstatus_init() should only be called during boot and the registers
> saved/restored across hart suspend. Looking at your branch, the other FWFT
> features have the same problem.

Hi Samuel, Yes indeed (And I think you already mentioned that on some
other series/meeting, sorry for that). I'll modify it on the fwft branch.

Thanks,

Clément

> 
> Regards,
> Samuel
> 
>> +
>> +	return SBI_SUCCESS;
>> +}
>> +
>> +static int sbi_get_double_trap_enable(struct fwft_config *conf,
>> +				      unsigned long *value)
>> +{
>> +	struct sbi_scratch *scratch = sbi_scratch_thishart_ptr();
>> +
>> +	if (!sbi_hart_has_extension(scratch, SBI_HART_EXT_SSDBLTRP))
>> +		return SBI_ENOTSUPP;
>> +
>> +	*value = (csr_read(CSR_MENVCFG_DBLTRP) & DBLTRP_DTE) != 0;
>> +
>> +	return SBI_SUCCESS;
>> +}
>>  
>>  static struct fwft_config* get_feature_config(enum sbi_fwft_feature_t feature)
>>  {
>> @@ -223,6 +268,12 @@ static const struct fwft_feature features[] =
>>  		.set = sbi_set_misaligned_delegation,
>>  		.get = sbi_get_misaligned_delegation,
>>  	},
>> +	{
>> +		.id = SBI_FWFT_DOUBLE_TRAP,
>> +		.supported = sbi_double_trap_supported,
>> +		.set = sbi_set_double_trap_enable,
>> +		.get = sbi_get_double_trap_enable,
>> +	},
>>  	{
>>  		.id = SBI_FWFT_USEED,
>>  		.supported = sbi_useed_supported,
>