Re: [PATCH 14/33] arm_mpam: Probe hardware to find the supported partid/pmg values

Ben Horgan
2025-11-13T16:43:39Z

Hi Fenghua,

On 11/13/25 03:50, Fenghua Yu wrote:
> Hi, Ben and James,
>
> On 11/7/25 04:34, Ben Horgan wrote:
>> From: James Morse <james.morse@arm.com>
> [SNIP]
>
>> +static struct mpam_msc_ris *mpam_get_or_create_ris(struct mpam_msc *msc,
>> +                           u8 ris_idx)
>> +{
>> +    int err;
>> +    struct mpam_msc_ris *ris;
>> +
>> +    lockdep_assert_held(&mpam_list_lock);
>> +
>> +    if (!test_bit(ris_idx, &msc->ris_idxs)) {
>> +        err = mpam_ris_create_locked(msc, ris_idx, MPAM_CLASS_UNKNOWN,
>> +                         0, 0);
>> +        if (err)
>> +            return ERR_PTR(err);
>> +    }
>> +
>> +    list_for_each_entry(ris, &msc->ris, msc_list) {
>> +        if (ris->ris_idx == ris_idx)
>> +            return ris;
>> +    }
>> +
>> +    return ERR_PTR(-ENOENT);
>> +}
>> +
>>   static int mpam_msc_hw_probe(struct mpam_msc *msc)
>>   {
>>       u64 idr;
>> +    u16 partid_max;
>> +    u8 ris_idx, pmg_max;
>> +    struct mpam_msc_ris *ris;
>>       struct device *dev = &msc->pdev->dev;
>>         lockdep_assert_held(&msc->probe_lock);
>> @@ -464,6 +564,40 @@ static int mpam_msc_hw_probe(struct mpam_msc *msc)
>>           return -EIO;
>>       }
>>   +    /* Grab an IDR value to find out how many RIS there are */
>> +    mutex_lock(&msc->part_sel_lock);
>> +    idr = mpam_msc_read_idr(msc);
>> +    mutex_unlock(&msc->part_sel_lock);
>> +
>> +    msc->ris_max = FIELD_GET(MPAMF_IDR_RIS_MAX, idr);
>> +
>> +    /* Use these values so partid/pmg always starts with a valid
>> value */
>> +    msc->partid_max = FIELD_GET(MPAMF_IDR_PARTID_MAX, idr);
>> +    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);
>> +        idr = mpam_msc_read_idr(msc);
>> +        mutex_unlock(&msc->part_sel_lock);
>> +
>> +        partid_max = FIELD_GET(MPAMF_IDR_PARTID_MAX, idr);
>> +        pmg_max = FIELD_GET(MPAMF_IDR_PMG_MAX, idr);
>> +        msc->partid_max = min(msc->partid_max, partid_max);
>> +        msc->pmg_max = min(msc->pmg_max, pmg_max);
>> +
>> +        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);
>
> It's better to destroy ris's that were previously created before this
> failed ris? Otherwise, there is a memory leak for those allocated ris's?

This should be handled by mpam_disable() which is run on probe failure.

>
> Thanks.
>
> -Fenghua

Thanks,

Ben