Re: [PATCH v2 06/15] arm_mpam: propagate MSC read errors for __ris_msmon_read()

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

Hi Andre,

On 7/2/26 17:22, Andre Przywara wrote:
> Allow the function for RIS accesses 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 | 35 +++++++++++++++++++++++++++-------
>  1 file changed, 28 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c
> index b259fe20a614..d18c7be86aaa 100644
> --- a/drivers/resctrl/mpam_devices.c
> +++ b/drivers/resctrl/mpam_devices.c
> @@ -1285,9 +1285,14 @@ static u64 mpam_msmon_overflow_val(enum mpam_device_features type,
>  	return overflow_val;
>  }
>  
> +/*
> + * This function might be called via smp_call_function_any(), so propagate
> + * errors inside the arg struct.
> + */
>  static void __ris_msmon_read(void *arg)
>  {
>  	u64 now;
> +	int ret;
>  	u32 now32;
>  	bool nrdy = false;
>  	bool config_mismatch;
> @@ -1326,7 +1331,9 @@ static void __ris_msmon_read(void *arg)
>  	 * Read the existing configuration to avoid re-writing the same values.
>  	 * This saves waiting for 'nrdy' on subsequent reads.
>  	 */
> -	read_msmon_ctl_flt_vals(m, &cur_ctl, &cur_flt);
> +	ret = read_msmon_ctl_flt_vals(m, &cur_ctl, &cur_flt);
> +	if (ret)
> +		goto out_unlock;
>  
>  	if (mpam_feat_msmon_mbwu_31counter == m->type)
>  		overflow = cur_ctl & MSMON_CFG_x_CTL_OFLOW_STATUS;
> @@ -1351,7 +1358,9 @@ static void __ris_msmon_read(void *arg)
>  
>  	switch (m->type) {
>  	case mpam_feat_msmon_csu:
> -		mpam_read_monsel_reg(msc, CSU, &now32);
> +		ret = mpam_read_monsel_reg(msc, CSU, &now32);
> +		if (ret)
> +			goto out_unlock;
>  		nrdy = now32 & MSMON___NRDY;
>  		now = FIELD_GET(MSMON___VALUE, now32);
>  
> @@ -1371,7 +1380,9 @@ static void __ris_msmon_read(void *arg)
>  			else
>  				now = FIELD_GET(MSMON___L_VALUE, now);
>  		} else {
> -			mpam_read_monsel_reg(msc, MBWU, &now32);
> +			ret = mpam_read_monsel_reg(msc, MBWU, &now32);
> +			if (ret)
> +				goto out_unlock;
>  			nrdy = now32 & MSMON___NRDY;
>  			now = FIELD_GET(MSMON___VALUE, now32);
>  		}
> @@ -1402,10 +1413,15 @@ static void __ris_msmon_read(void *arg)
>  	if (nrdy)
>  		m->err = -EBUSY;
>  
> -	if (m->err)
> -		return;
> +	if (!m->err)
> +		*m->val += now;

Why does this change? Can't you keep this the 'if' statement as before
and more the 'return' after the '*m->val += now;'?

Thanks,

Ben

> +
> +	return;
>  
> -	*m->val += now;
> +out_unlock:
> +	mpam_mon_sel_unlock(msc);
> +
> +	m->err = ret;
>  }
>  
>  static int _msmon_read(struct mpam_component *comp, struct mon_read *arg)
> @@ -1729,6 +1745,7 @@ static int mpam_restore_mbwu_state(void *_ris)
>  {
>  	int i;
>  	u64 val;
> +	int ret = 0;
>  	struct mon_read mwbu_arg;
>  	struct mpam_msc_ris *ris = _ris;
>  	struct mpam_class *class = ris->vmsc->comp->class;
> @@ -1741,10 +1758,14 @@ static int mpam_restore_mbwu_state(void *_ris)
>  			mwbu_arg.val = &val;
>  
>  			__ris_msmon_read(&mwbu_arg);
> +			if (mwbu_arg.err) {
> +				ret = mwbu_arg.err;
> +				break;
> +			}
>  		}
>  	}
>  
> -	return 0;
> +	return ret;
>  }
>  
>  /* Call with MSC cfg_lock held */