[PATCH v3 2/4] lib: sbi: fwft: add support for SBI_FWFT_MISALIGNED_EXC_DELEG

[Andrew Jones]

On Wed, Jun 19, 2024 at 11:42:40AM GMT, Clément Léger wrote:
> Add support for SBI_FWFT_MISALIGNED_EXC_DELEG withing FWFT support. This
> support allows to delegate misaligned accesses traps.
> 
> Signed-off-by: Clément Léger <cleger at rivosinc.com>
> ---
>  lib/sbi/sbi_fwft.c | 39 ++++++++++++++++++++++++++++++++++++++-
>  lib/sbi/sbi_hsm.c  |  3 +++
>  2 files changed, 41 insertions(+), 1 deletion(-)
> 
> diff --git a/lib/sbi/sbi_fwft.c b/lib/sbi/sbi_fwft.c
> index b302b5d..289a344 100644
> --- a/lib/sbi/sbi_fwft.c
> +++ b/lib/sbi/sbi_fwft.c
> @@ -32,6 +32,8 @@ static unsigned long fwft_ptr_offset;
>  #define fwft_set_hart_state_ptr(__scratch, __phs)			\
>  	sbi_scratch_write_type((__scratch), void *, fwft_ptr_offset, (__phs))
>  
> +#define MIS_DELEG (1UL << CAUSE_MISALIGNED_LOAD | 1UL << CAUSE_MISALIGNED_STORE)
> +
>  struct fwft_config;
>  
>  struct fwft_feature {
> @@ -71,6 +73,33 @@ static bool fwft_is_defined_feature(enum sbi_fwft_feature_t feature)
>  	return false;
>  }
>  
> +static int fwft_misaligned_delegation_supported(struct fwft_config *conf)
> +{
> +	if (!misa_extension('S'))
> +		return SBI_ENOTSUPP;
> +
> +	return SBI_OK;
> +}
> +
> +static int fwft_set_misaligned_delegation(struct fwft_config *conf,
> +					 unsigned long value)
> +{
> +	if (value)
> +		csr_set(CSR_MEDELEG, MIS_DELEG);
> +	else
> +		csr_clear(CSR_MEDELEG, MIS_DELEG);

Sorry for my late review. This should be

  if (value == 1)
     csr_set(CSR_MEDELEG, MIS_DELEG);
  else if (value == 0)
     csr_clear(CSR_MEDELEG, MIS_DELEG);
  else
     return SBI_EINVAL;

It's unlikely we'll ever extend the inputs/behaviors, but if we don't
check for the inputs explicitly now, then we never can.

And same comment for SBI_FWFT_PTE_AD_HW_UPDATING.

Thanks,
drew

> +
> +	return SBI_OK;
> +}
> +
> +static int fwft_get_misaligned_delegation(struct fwft_config *conf,
> +					 unsigned long *value)
> +{
> +	*value = (csr_read(CSR_MEDELEG) & MIS_DELEG) != 0;
> +
> +	return SBI_OK;
> +}
> +
>  static struct fwft_config* get_feature_config(enum sbi_fwft_feature_t feature)
>  {
>  	int i;
> @@ -148,7 +177,15 @@ int sbi_fwft_get(enum sbi_fwft_feature_t feature, unsigned long *out_val)
>  	return conf->feature->get(conf, out_val);
>  }
>  
> -static const struct fwft_feature features[] = {};
> +static const struct fwft_feature features[] =
> +{
> +	{
> +		.id = SBI_FWFT_MISALIGNED_EXC_DELEG,
> +		.supported = fwft_misaligned_delegation_supported,
> +		.set = fwft_set_misaligned_delegation,
> +		.get = fwft_get_misaligned_delegation,
> +	},
> +};
>  
>  int sbi_fwft_init(struct sbi_scratch *scratch, bool cold_boot)
>  {
> diff --git a/lib/sbi/sbi_hsm.c b/lib/sbi/sbi_hsm.c
> index be48d64..2b23e13 100644
> --- a/lib/sbi/sbi_hsm.c
> +++ b/lib/sbi/sbi_hsm.c
> @@ -44,6 +44,7 @@ struct sbi_hsm_data {
>  	unsigned long suspend_type;
>  	unsigned long saved_mie;
>  	unsigned long saved_mip;
> +	unsigned long saved_medeleg;
>  	atomic_t start_ticket;
>  };
>  
> @@ -417,6 +418,7 @@ void __sbi_hsm_suspend_non_ret_save(struct sbi_scratch *scratch)
>  
>  	hdata->saved_mie = csr_read(CSR_MIE);
>  	hdata->saved_mip = csr_read(CSR_MIP) & (MIP_SSIP | MIP_STIP);
> +	hdata->saved_medeleg = csr_read(CSR_MEDELEG);
>  }
>  
>  static void __sbi_hsm_suspend_non_ret_restore(struct sbi_scratch *scratch)
> @@ -424,6 +426,7 @@ static void __sbi_hsm_suspend_non_ret_restore(struct sbi_scratch *scratch)
>  	struct sbi_hsm_data *hdata = sbi_scratch_offset_ptr(scratch,
>  							    hart_data_offset);
>  
> +	csr_write(CSR_MEDELEG, hdata->saved_medeleg);
>  	csr_write(CSR_MIE, hdata->saved_mie);
>  	csr_set(CSR_MIP, (hdata->saved_mip & (MIP_SSIP | MIP_STIP)));
>  }
> -- 
> 2.45.2
> 
> 
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