[PATCH v11 02/13] arm_mpam: propagate MSC access errors for hw_probe functions
Andre Przywara
andre.przywara at arm.com
Wed Sep 30 08:57:50 PDT 2026
Hi Ben,
On 9/30/26 16:01, Ben Horgan wrote:
> Hi Andre,
>
> On 24/09/2026 16:27, Andre Przywara wrote:
>> Allow the functions probing for MSC hardware and features to return an
>> error, and propagate read and write errors from the lower level up.
>> This uses some "scoped cleanup" functions like scoped_guard() and
>> ACQUIRE() to avoid the complexity of error handling when a lock has been
>> taken. Since the mon_sel_lock is a bit special (even more so in an
>> upcoming patch), we define a new GUARD type for it.
>>
>> Signed-off-by: Andre Przywara <andre.przywara at arm.com>
>> Reviewed-by: Jonathan Cameron <jonathan.cameron at oss.qualcomm.com>
>> Reviewed-by: Ben Horgan <ben.horgan at arm.com>
>> Reviewed-by: Gavin Shan <gshan at redhat.com>
>> Tested-by: Gavin Shan <gshan at redhat.com> # on NVIDIA Grace Hopper
>> ---
>> drivers/resctrl/mpam_devices.c | 126 +++++++++++++++++++++-----------
>> drivers/resctrl/mpam_internal.h | 4 +
>> 2 files changed, 87 insertions(+), 43 deletions(-)
>>
>> diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c
>> index c7686d3799653..22069e7f7bb05 100644
>> --- a/drivers/resctrl/mpam_devices.c
>> +++ b/drivers/resctrl/mpam_devices.c
>> @@ -798,38 +798,46 @@ static bool mpam_ris_hw_probe_csu_nrdy(struct mpam_msc_ris *ris)
>> bool can_set, can_clear;
>> struct mpam_msc *msc = ris->vmsc->msc;
>>
>> - if (WARN_ON_ONCE(!mpam_mon_sel_lock(msc)))
>> + ACQUIRE(mon_sel_lock, guard)(msc);
>> + if (ACQUIRE_ERR(mon_sel_lock, &guard))
>> return false;
>>
>> mon_sel = FIELD_PREP(MSMON_CFG_MON_SEL_MON_SEL, 0) |
>> FIELD_PREP(MSMON_CFG_MON_SEL_RIS, ris->ris_idx);
>> - mpam_write_monsel_reg(msc, CFG_MON_SEL, mon_sel);
>> + if (mpam_write_monsel_reg(msc, CFG_MON_SEL, mon_sel))
>> + return false;
>>
>> /* Hardware might ignore nrdy if it's not enabled */
>> ctl_val = MSMON_CFG_CSU_CTL_TYPE_CSU;
>> ctl_val |= MSMON_CFG_x_CTL_MATCH_PARTID;
>> ctl_val |= MSMON_CFG_x_CTL_MATCH_PMG;
>> ctl_val |= MSMON_CFG_x_CTL_EN;
>> - mpam_write_monsel_reg(msc, CFG_CSU_FLT, 0);
>> - mpam_write_monsel_reg(msc, CFG_CSU_CTL, ctl_val);
>> + if (mpam_write_monsel_reg(msc, CFG_CSU_FLT, 0))
>> + return false;
>> + if (mpam_write_monsel_reg(msc, CFG_CSU_CTL, ctl_val))
>> + return false;
>>
>> - _mpam_write_monsel_reg(msc, MSMON_CSU, MSMON___NRDY);
>> - _mpam_read_monsel_reg(msc, MSMON_CSU, &now);
>> + if (_mpam_write_monsel_reg(msc, MSMON_CSU, MSMON___NRDY))
>> + return false;
>> + if (_mpam_read_monsel_reg(msc, MSMON_CSU, &now))
>> + return false;
>> can_set = now & MSMON___NRDY;
>>
>> - _mpam_write_monsel_reg(msc, MSMON_CSU, 0);
>> + if (_mpam_write_monsel_reg(msc, MSMON_CSU, 0))
>> + return false;
>> /* 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_write_monsel_reg(msc, CFG_CSU_FLT, 0x1))
>> + return false;
>> + 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);
>> }
>
> I've had a look at the Sashiko reports [1] for these patches. I'll call out the things that I feel
> need answering.
>
> As sashiko says, mpam_ris_hw_probe_csu_nrdy(), this swallows the error rather than propagating. It
> would be better if this returned success/error and the answer to whether or not the h/w supports
> nrdy separately. As we make other accesses to the msc later it is unlikely this will ever cause a
> failing probe to report success though.
Well, what I could offer is to make mpam_ris_hw_probe_csu_nrdy() return
an int, with negative values meaning an error, 0 meaning false, and 1
being true.
Then, in the caller, do:
err = mpam_ris_hw_probe_csu_nrdy(ris);
if (err < 0)
return err;
hw_managed = err;
I think a fairly straight-forward change, does this sound OK?
Cheers,
Andre
>
> Thanks,
>
> Ben
>
> [1] https://sashiko.dev/#/patchset/20260924152739.2865510-1-andre.przywara%40arm.com
>
>>
>> -static void mpam_ris_hw_probe(struct mpam_msc_ris *ris)
>> +static int mpam_ris_hw_probe(struct mpam_msc_ris *ris)
>> {
>> - int err;
>> + int fw_has_nrdy_err, err;
>> struct mpam_msc *msc = ris->vmsc->msc;
>> struct device *dev = &msc->pdev->dev;
>> struct mpam_props *props = &ris->props;
>> @@ -842,7 +850,9 @@ 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 &&
>> @@ -867,7 +877,9 @@ 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)
>> @@ -877,8 +889,9 @@ 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);
>> @@ -907,8 +920,9 @@ 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)) {
>> @@ -929,20 +943,24 @@ 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
>> * CSU counters can't be used. Should we wait forever?
>> */
>> - err = device_property_read_u32(&msc->pdev->dev,
>> - "arm,not-ready-us",
>> - &msc->nrdy_usec);
>> + fw_has_nrdy_err = device_property_read_u32(&msc->pdev->dev,
>> + "arm,not-ready-us",
>> + &msc->nrdy_usec);
>>
>> 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) {
>> @@ -960,7 +978,7 @@ static void mpam_ris_hw_probe(struct mpam_msc_ris *ris)
>> * Accept the missing firmware property if NRDY appears
>> * un-implemented.
>> */
>> - if (err && hw_managed)
>> + if (fw_has_nrdy_err && hw_managed)
>> dev_err_once(dev, "Counters are not usable because not-ready timeout was not provided by firmware.");
>> }
>> }
>> @@ -968,7 +986,9 @@ 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) {
>> @@ -1001,16 +1021,22 @@ 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;
>> @@ -1025,11 +1051,15 @@ 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);
>> + scoped_guard(mutex, &msc->part_sel_lock) {
>> + ret = mpam_msc_read_idr(msc, &idr);
>> + if (ret)
>> + return ret;
>>
>> - mutex_unlock(&msc->part_sel_lock);
>> + ret = mpam_read_partsel_reg(msc, IIDR, &msc->iidr);
>> + if (ret)
>> + return ret;
>> + }
>>
>> mpam_enable_quirks(msc);
>>
>> @@ -1040,10 +1070,15 @@ static int mpam_msc_hw_probe(struct mpam_msc *msc)
>> msc->pmg_max = FIELD_GET(MPAMF_IDR_PMG_MAX, idr);
>>
>> 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);
>> - mutex_unlock(&msc->part_sel_lock);
>> + scoped_guard(mutex, &msc->part_sel_lock) {
>> + ret = __mpam_part_sel(ris_idx, 0, msc);
>> + if (ret)
>> + return ret;
>> +
>> + ret = mpam_msc_read_idr(msc, &idr);
>> + if (ret)
>> + return ret;
>> + }
>>
>> partid_max = FIELD_GET(MPAMF_IDR_PARTID_MAX, idr);
>> pmg_max = FIELD_GET(MPAMF_IDR_PMG_MAX, idr);
>> @@ -1051,17 +1086,22 @@ static int mpam_msc_hw_probe(struct mpam_msc *msc)
>> msc->pmg_max = min(msc->pmg_max, pmg_max);
>> msc->has_extd_esr = FIELD_GET(MPAMF_IDR_HAS_EXTD_ESR, idr);
>>
>> - mutex_lock(&mpam_list_lock);
>> - ris = mpam_get_or_create_ris(msc, ris_idx);
>> - mutex_unlock(&mpam_list_lock);
>> - if (IS_ERR(ris))
>> - return PTR_ERR(ris);
>> + scoped_guard(mutex, &mpam_list_lock) {
>> + ris = mpam_get_or_create_ris(msc, ris_idx);
>> + if (IS_ERR(ris))
>> + return PTR_ERR(ris);
>> + }
>> ris->idr = idr;
>>
>> - mutex_lock(&msc->part_sel_lock);
>> - __mpam_part_sel(ris_idx, 0, msc);
>> - mpam_ris_hw_probe(ris);
>> - mutex_unlock(&msc->part_sel_lock);
>> + scoped_guard(mutex, &msc->part_sel_lock) {
>> + ret = __mpam_part_sel(ris_idx, 0, msc);
>> + if (ret)
>> + return ret;
>> +
>> + ret = mpam_ris_hw_probe(ris);
>> + if (ret)
>> + return ret;
>> + }
>> }
>>
>> /* Clear any stale errors */
>> diff --git a/drivers/resctrl/mpam_internal.h b/drivers/resctrl/mpam_internal.h
>> index def0e3a65c230..68a6cf2b9cc73 100644
>> --- a/drivers/resctrl/mpam_internal.h
>> +++ b/drivers/resctrl/mpam_internal.h
>> @@ -162,6 +162,10 @@ static inline void mpam_mon_sel_lock_init(struct mpam_msc *msc)
>> raw_spin_lock_init(&msc->_mon_sel_lock);
>> }
>>
>> +DEFINE_GUARD(mon_sel, struct mpam_msc *,
>> + mpam_mon_sel_lock(_T), mpam_mon_sel_unlock(_T));
>> +DEFINE_GUARD_COND(mon_sel, _lock, mpam_mon_sel_lock(_T), _RET);
>> +
>> /* Bits for mpam features bitmaps */
>> enum mpam_device_features {
>> mpam_feat_cpor_part,
>
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