[PATCH v2 03/15] arm_mpam: propagate MSC read errors for hw_probe functions
Andre Przywara
andre.przywara at arm.com
Thu Jul 9 00:35:37 PDT 2026
Hi Ben,
thanks for having a thorough look!
On 7/1/26 22:00, Ben Horgan wrote:
> Hi Andre,
>
> On 7/2/26 17:22, Andre Przywara wrote:
>> Allow the functions probing for MSC hardware and features to return an
>> error, and propagate read errors from the lower level up.
>>
>> Signed-off-by: Andre Przywara <andre.przywara at arm.com>
>> ---
>> drivers/resctrl/mpam_devices.c | 62 ++++++++++++++++++++++++----------
>> 1 file changed, 44 insertions(+), 18 deletions(-)
>>
>> diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c
>> index ce8738adb6ff..011d1e3544d7 100644
>> --- a/drivers/resctrl/mpam_devices.c
>> +++ b/drivers/resctrl/mpam_devices.c
>> @@ -800,20 +800,22 @@ static bool mpam_ris_hw_probe_csu_nrdy(struct mpam_msc_ris *ris)
>> mpam_write_monsel_reg(msc, CFG_CSU_CTL, ctl_val);
>>
>> _mpam_write_monsel_reg(msc, MSMON_CSU, MSMON___NRDY);
>> - _mpam_read_monsel_reg(msc, MSMON_CSU, &now);
>> + if (_mpam_read_monsel_reg(msc, MSMON_CSU, &now))
>> + return false;
>
> This early return leaves the mon_sel lock held.
Ouch, well spotted. I think this "if (WARN_ON_ONCE(...))" wrapper
distracted me from the lock...
Changed it to use "goto out_unlock;"
>
>> can_set = now & MSMON___NRDY;
>
> As you're adding early returns to this function does it make sense to
> return early if can_set is false?
Well, this could have been done before as well, but it executes the
remaining accesses nevertheless. I don't feel like judging whether this
has a side effect, so just mimicked the current behaviour.
I feel like this should be a separate patch, if we need it.
Thanks,
Andre
>>
>> _mpam_write_monsel_reg(msc, MSMON_CSU, 0);
>> /* Configuration change to try and coax hardware into setting nrdy */
>> mpam_write_monsel_reg(msc, CFG_CSU_FLT, 0x1);
>> - _mpam_read_monsel_reg(msc, MSMON_CSU, &now);
>> + if (_mpam_read_monsel_reg(msc, MSMON_CSU, &now))
>> + return false;
>> can_clear = !(now & MSMON___NRDY);
>> mpam_mon_sel_unlock(msc);
>>
>> return (!can_set || !can_clear);
>> }
>>
>> -static void mpam_ris_hw_probe(struct mpam_msc_ris *ris)
>> +static int mpam_ris_hw_probe(struct mpam_msc_ris *ris)
>> {
>> int err;
>> struct mpam_msc *msc = ris->vmsc->msc;
>> @@ -828,7 +830,9 @@ static void mpam_ris_hw_probe(struct mpam_msc_ris *ris)
>> if (FIELD_GET(MPAMF_IDR_HAS_CCAP_PART, ris->idr)) {
>> u32 ccap_features;
>>
>> - mpam_read_partsel_reg(msc, CCAP_IDR, &ccap_features);
>> + err = mpam_read_partsel_reg(msc, CCAP_IDR, &ccap_features);
>> + if (err)
>> + return err;
>>
>> props->cmax_wd = FIELD_GET(MPAMF_CCAP_IDR_CMAX_WD, ccap_features);
>> if (props->cmax_wd &&
>> @@ -853,7 +857,9 @@ static void mpam_ris_hw_probe(struct mpam_msc_ris *ris)
>> if (FIELD_GET(MPAMF_IDR_HAS_CPOR_PART, ris->idr)) {
>> u32 cpor_features;
>>
>> - mpam_read_partsel_reg(msc, CPOR_IDR, &cpor_features);
>> + err = mpam_read_partsel_reg(msc, CPOR_IDR, &cpor_features);
>> + if (err)
>> + return err;
>>
>> props->cpbm_wd = FIELD_GET(MPAMF_CPOR_IDR_CPBM_WD, cpor_features);
>> if (props->cpbm_wd)
>> @@ -863,8 +869,9 @@ static void mpam_ris_hw_probe(struct mpam_msc_ris *ris)
>> /* Memory bandwidth partitioning */
>> if (FIELD_GET(MPAMF_IDR_HAS_MBW_PART, ris->idr)) {
>> u32 mbw_features;
>> -
>> - mpam_read_partsel_reg(msc, MBW_IDR, &mbw_features);
>> + err = mpam_read_partsel_reg(msc, MBW_IDR, &mbw_features);
>> + if (err)
>> + return err;
>>
>> /* portion bitmap resolution */
>> props->mbw_pbm_bits = FIELD_GET(MPAMF_MBW_IDR_BWPBM_WD, mbw_features);
>> @@ -893,8 +900,9 @@ static void mpam_ris_hw_probe(struct mpam_msc_ris *ris)
>> /* Priority partitioning */
>> if (FIELD_GET(MPAMF_IDR_HAS_PRI_PART, ris->idr)) {
>> u32 pri_features;
>> -
>> - mpam_read_partsel_reg(msc, PRI_IDR, &pri_features);
>> + err = mpam_read_partsel_reg(msc, PRI_IDR, &pri_features);
>> + if (err)
>> + return err;
>>
>> props->intpri_wd = FIELD_GET(MPAMF_PRI_IDR_INTPRI_WD, pri_features);
>> if (props->intpri_wd && FIELD_GET(MPAMF_PRI_IDR_HAS_INTPRI, pri_features)) {
>> @@ -915,7 +923,9 @@ static void mpam_ris_hw_probe(struct mpam_msc_ris *ris)
>> if (FIELD_GET(MPAMF_IDR_HAS_MSMON, ris->idr)) {
>> u32 msmon_features;
>>
>> - mpam_read_partsel_reg(msc, MSMON_IDR, &msmon_features);
>> + err = mpam_read_partsel_reg(msc, MSMON_IDR, &msmon_features);
>> + if (err)
>> + return err;
>>
>> /*
>> * If the firmware max-nrdy-us property is missing, the
>> @@ -928,7 +938,9 @@ static void mpam_ris_hw_probe(struct mpam_msc_ris *ris)
>> if (FIELD_GET(MPAMF_MSMON_IDR_MSMON_CSU, msmon_features)) {
>> u32 csumonidr;
>>
>> - mpam_read_partsel_reg(msc, CSUMON_IDR, &csumonidr);
>> + err = mpam_read_partsel_reg(msc, CSUMON_IDR, &csumonidr);
>> + if (err)
>> + return err;
>>
>> props->num_csu_mon = FIELD_GET(MPAMF_CSUMON_IDR_NUM_MON, csumonidr);
>> if (props->num_csu_mon) {
>> @@ -954,7 +966,9 @@ static void mpam_ris_hw_probe(struct mpam_msc_ris *ris)
>> bool has_long;
>> u32 mbwumon_idr;
>>
>> - mpam_read_partsel_reg(msc, MBWUMON_IDR, &mbwumon_idr);
>> + err = mpam_read_partsel_reg(msc, MBWUMON_IDR, &mbwumon_idr);
>> + if (err)
>> + return err;
>>
>> props->num_mbwu_mon = FIELD_GET(MPAMF_MBWUMON_IDR_NUM_MON, mbwumon_idr);
>> if (props->num_mbwu_mon) {
>> @@ -987,16 +1001,22 @@ static void mpam_ris_hw_probe(struct mpam_msc_ris *ris)
>> u16 partid_max;
>> u32 nrwidr;
>>
>> - mpam_read_partsel_reg(msc, PARTID_NRW_IDR, &nrwidr);
>> + err = mpam_read_partsel_reg(msc, PARTID_NRW_IDR, &nrwidr);
>> + if (err)
>> + return err;
>> +
>> partid_max = FIELD_GET(MPAMF_PARTID_NRW_IDR_INTPARTID_MAX, nrwidr);
>>
>> mpam_set_feature(mpam_feat_partid_nrw, props);
>> msc->partid_max = min(msc->partid_max, partid_max);
>> }
>> +
>> + return 0;
>> }
>>
>> static int mpam_msc_hw_probe(struct mpam_msc *msc)
>> {
>> + int ret;
>> u64 idr;
>> u16 partid_max;
>> u8 ris_idx, pmg_max;
>> @@ -1012,10 +1032,12 @@ static int mpam_msc_hw_probe(struct mpam_msc *msc)
>>
>> /* Grab an IDR value to find out how many RIS there are */
>> mutex_lock(&msc->part_sel_lock);
>> - mpam_msc_read_idr(msc, &idr);
>> - mpam_read_partsel_reg(msc, IIDR, &msc->iidr);
>> -
>> + ret = mpam_msc_read_idr(msc, &idr);
>> + if (!ret)
>> + ret = mpam_read_partsel_reg(msc, IIDR, &msc->iidr);
>> mutex_unlock(&msc->part_sel_lock);
>> + if (ret)
>> + return ret;
>>
>> mpam_enable_quirks(msc);
>>
>> @@ -1028,8 +1050,10 @@ static int mpam_msc_hw_probe(struct mpam_msc *msc)
>> for (ris_idx = 0; ris_idx <= msc->ris_max; ris_idx++) {
>> mutex_lock(&msc->part_sel_lock);
>> __mpam_part_sel(ris_idx, 0, msc);
>> - mpam_msc_read_idr(msc, &idr);
>> + ret = mpam_msc_read_idr(msc, &idr);
>> mutex_unlock(&msc->part_sel_lock);
>> + if (ret)
>> + return ret;
>>
>> partid_max = FIELD_GET(MPAMF_IDR_PARTID_MAX, idr);
>> pmg_max = FIELD_GET(MPAMF_IDR_PMG_MAX, idr);
>> @@ -1046,8 +1070,10 @@ static int mpam_msc_hw_probe(struct mpam_msc *msc)
>>
>> mutex_lock(&msc->part_sel_lock);
>> __mpam_part_sel(ris_idx, 0, msc);
>> - mpam_ris_hw_probe(ris);
>> + ret = mpam_ris_hw_probe(ris);
>> mutex_unlock(&msc->part_sel_lock);
>> + if (ret)
>> + return ret;
>> }
>>
>> /* Clear any stale errors */
>
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