Re: [PATCH v2 07/15] arm_mpam: propagate MSC read errors for state saving functions

[Ben Horgan <ben.horgan@arm.com>]

Hi Andre,

On 7/2/26 17:22, Andre Przywara wrote:
> Allow the mpam_save_mbwu_state() function to return an error, and
> propagate read errors from the lower level up.
> 
> Signed-off-by: Andre Przywara <andre.przywara@arm.com>
> ---
>  drivers/resctrl/mpam_devices.c | 47 +++++++++++++++++++++-------------
>  1 file changed, 29 insertions(+), 18 deletions(-)
> 
> diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c
> index d18c7be86aaa..c50ca0e4f426 100644
> --- a/drivers/resctrl/mpam_devices.c
> +++ b/drivers/resctrl/mpam_devices.c
> @@ -1773,6 +1773,7 @@ static int mpam_save_mbwu_state(void *arg)
>  {
>  	int i;
>  	u64 val;
> +	int ret;
>  	struct mon_cfg *cfg;
>  	u32 cur_flt, cur_ctl, mon_sel;
>  	struct mpam_msc_ris *ris = arg;
> @@ -1789,31 +1790,41 @@ static int mpam_save_mbwu_state(void *arg)
>  		mon_sel = FIELD_PREP(MSMON_CFG_MON_SEL_MON_SEL, i) |
>  			  FIELD_PREP(MSMON_CFG_MON_SEL_RIS, ris->ris_idx);
>  		mpam_write_monsel_reg(msc, CFG_MON_SEL, mon_sel);
> -		mpam_read_monsel_reg(msc, CFG_MBWU_FLT, &cur_flt);
> -		mpam_read_monsel_reg(msc, CFG_MBWU_CTL, &cur_ctl);
> -		mpam_write_monsel_reg(msc, CFG_MBWU_CTL, 0);
> +		ret = mpam_read_monsel_reg(msc, CFG_MBWU_FLT, &cur_flt);
> +		if (!ret)
> +			ret = mpam_read_monsel_reg(msc, CFG_MBWU_CTL, &cur_ctl);
> +		if (!ret)
> +			mpam_write_monsel_reg(msc, CFG_MBWU_CTL, 0);
>  
> -		if (mpam_ris_has_mbwu_long_counter(ris)) {
> -			val = mpam_msc_read_mbwu_l(msc);
> -			mpam_msc_zero_mbwu_l(msc);
> -		} else {
> -			u32 val32;
> +		if (!ret) {
> +			if (mpam_ris_has_mbwu_long_counter(ris)) {
> +				val = mpam_msc_read_mbwu_l(msc);
> +				mpam_msc_zero_mbwu_l(msc);
> +			} else {
> +				u32 val32;
>  
> -			mpam_read_monsel_reg(msc, MBWU, &val32);
> -			val = val32;
> -			mpam_write_monsel_reg(msc, MBWU, 0);
> +				ret = mpam_read_monsel_reg(msc, MBWU, &val32);
> +				if (!ret) {
> +					val = val32;
> +					mpam_write_monsel_reg(msc, MBWU, 0);
> +				}
> +			}
>  		}
>  
> -		cfg->mon = i;
> -		cfg->pmg = FIELD_GET(MSMON_CFG_x_FLT_PMG, cur_flt);
> -		cfg->match_pmg = FIELD_GET(MSMON_CFG_x_CTL_MATCH_PMG, cur_ctl);
> -		cfg->partid = FIELD_GET(MSMON_CFG_x_FLT_PARTID, cur_flt);
> -		mbwu_state->correction += val;
> -		mbwu_state->enabled = FIELD_GET(MSMON_CFG_x_CTL_EN, cur_ctl);
> +		if (!ret && val != MSMON___L_NRDY) {
> +			cfg->mon = i;
> +			cfg->pmg = FIELD_GET(MSMON_CFG_x_FLT_PMG, cur_flt);
> +			cfg->match_pmg = FIELD_GET(MSMON_CFG_x_CTL_MATCH_PMG, cur_ctl);
> +			cfg->partid = FIELD_GET(MSMON_CFG_x_FLT_PARTID, cur_flt);
> +			mbwu_state->correction += val;
> +			mbwu_state->enabled = FIELD_GET(MSMON_CFG_x_CTL_EN, cur_ctl);
> +		}
>  		mpam_mon_sel_unlock(msc);
> +		if (ret)
> +			break;

There is a lot of if(!ret) in this loop. Does it not end up cleaner to
add an out_unlock label after the loop and jump to that in the failure
cases?

Thanks,

Ben

>  	}
>  
> -	return 0;
> +	return ret;
>  }
>  
>  /*