[PATCH 17/33] arm_mpam: Probe the hardware features resctrl supports

[Ben Horgan]

Hi James,

On 9/9/25 17:57, James Morse wrote:
> Hi Ben,
> 
> On 28/08/2025 14:44, Ben Horgan wrote:
>> On 8/22/25 16:29, James Morse wrote:
>>> Expand the probing support with the control and monitor types
>>> we can use with resctrl.
> 
>>> diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c
>>> index 012e09e80300..290a04f8654f 100644
>>> --- a/drivers/resctrl/mpam_devices.c
>>> +++ b/drivers/resctrl/mpam_devices.c
>>> @@ -102,7 +102,7 @@ static LLIST_HEAD(mpam_garbage);
>>>  
>>>  static u32 __mpam_read_reg(struct mpam_msc *msc, u16 reg)
>>>  {
>>> -	WARN_ON_ONCE(reg > msc->mapped_hwpage_sz);
>>> +	WARN_ON_ONCE(reg + sizeof(u32) > msc->mapped_hwpage_sz);
> 
>> Update in the patch that introduced this line.
> 
> Yeah - this got ripped out.
> Now that the size is in the ACPI table, I should never need to debug it being wrong!
> (and the resulting translation fault will be enough to say something is wrong)
> 
> 
>>> diff --git a/drivers/resctrl/mpam_internal.h b/drivers/resctrl/mpam_internal.h
>>> index c6f087f9fa7d..9f6cd4a68cce 100644
>>> --- a/drivers/resctrl/mpam_internal.h
>>> +++ b/drivers/resctrl/mpam_internal.h
>>> @@ -136,6 +136,56 @@ static inline void mpam_mon_sel_lock_held(struct mpam_msc *msc)
> 
>>> +/* Bits for mpam_features_t */
>>> +enum mpam_device_features {
>>> +	mpam_feat_ccap_part = 0,
>>> +	mpam_feat_cpor_part,
>>> +	mpam_feat_mbw_part,
>>> +	mpam_feat_mbw_min,
>>> +	mpam_feat_mbw_max,
>>> +	mpam_feat_mbw_prop,
>>> +	mpam_feat_msmon,
>>> +	mpam_feat_msmon_csu,
>>> +	mpam_feat_msmon_csu_capture,
>>> +	mpam_feat_msmon_csu_hw_nrdy,
>>> +	mpam_feat_msmon_mbwu,
>>> +	mpam_feat_msmon_mbwu_capture,
>>> +	mpam_feat_msmon_mbwu_rwbw,
>>> +	mpam_feat_msmon_mbwu_hw_nrdy,
>>> +	mpam_feat_msmon_capt,
>>> +	MPAM_FEATURE_LAST,
> 
>> This isn't all the features or just the features supported by resctrl.
>> Just add them all in this patch?
> 
> I'm having trouble parsing this ...
> 
> I needed somewhere to split the features up, as there are rather a lot. Those that resctrl
> supports seemed like the logical spot.

I don't think resctrl doesn't support ccap, mpam_feat_ccap_part.
Possibly the point is that this is split into more detailed features
later but that's not clear from this patch or commit message.

> 
> 
>>> +};
>>> +static_assert(BITS_PER_TYPE(mpam_features_t) >= MPAM_FEATURE_LAST);
>>> +#define MPAM_ALL_FEATURES      ((1 << MPAM_FEATURE_LAST) - 1)
> 
>> Unused?
> 
> Fixed, thanks!
> 
> 
> Thanks,
> 
> James

Thanks,

Ben