Re: [PATCH v4 06/10] arm_mpam: propagate MSC access errors for state saving function

[Sudeep Holla]

On Thu, Jul 23, 2026 at 05:54:50PM +0200, Andre Przywara wrote:
> Allow the mpam_save_mbwu_state() function to return an error, and
> propagate read and write errors from the lower level up.
> 
> Signed-off-by: Andre Przywara <andre.przywara@xxxxxxx>
> ---
>  drivers/resctrl/mpam_devices.c | 29 ++++++++++++++++++++++-------
>  1 file changed, 22 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c
> index bcff53477133..6329443c451f 100644
> --- a/drivers/resctrl/mpam_devices.c
> +++ b/drivers/resctrl/mpam_devices.c
> @@ -1833,22 +1833,37 @@ 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_write_monsel_reg(msc, CFG_MON_SEL, mon_sel);
> +		if (ret)
> +			return ret;
> +		ret = mpam_read_monsel_reg(msc, CFG_MBWU_FLT, &cur_flt);
> +		if (ret)
> +			return ret;
> +		ret = mpam_read_monsel_reg(msc, CFG_MBWU_CTL, &cur_ctl);
> +		if (ret)
> +			return ret;

How does it work in general with PCC. Now that you can fail at any point,
what happens to the write that occurs before a failed read like above one.
Who will take care of erasing those new writes or it doesn't matter ?
Just checking as I don't have much knowledge on MPAM intrinsics.

-- 
Regards,
Sudeep