linux-kernel - Re: [PATCH 27/33] arm_mpam: Add mpam_msmon

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Message-ID: <761245fb-a045-4809-9fd9-5efc56794b37@arm.com>
Date: Wed, 10 Sep 2025 20:30:29 +0100
From: James Morse <james.morse@....com>
To: Ben Horgan <ben.horgan@....com>, linux-kernel@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, linux-acpi@...r.kernel.org,
 devicetree@...r.kernel.org
Cc: shameerali.kolothum.thodi@...wei.com,
 D Scott Phillips OS <scott@...amperecomputing.com>,
 carl@...amperecomputing.com, lcherian@...vell.com,
 bobo.shaobowang@...wei.com, tan.shaopeng@...itsu.com,
 baolin.wang@...ux.alibaba.com, Jamie Iles <quic_jiles@...cinc.com>,
 Xin Hao <xhao@...ux.alibaba.com>, peternewman@...gle.com,
 dfustini@...libre.com, amitsinght@...vell.com,
 David Hildenbrand <david@...hat.com>, Rex Nie <rex.nie@...uarmicro.com>,
 Dave Martin <dave.martin@....com>, Koba Ko <kobak@...dia.com>,
 Shanker Donthineni <sdonthineni@...dia.com>, fenghuay@...dia.com,
 baisheng.gao@...soc.com, Jonathan Cameron <jonathan.cameron@...wei.com>,
 Rob Herring <robh@...nel.org>, Rohit Mathew <rohit.mathew@....com>,
 Rafael Wysocki <rafael@...nel.org>, Len Brown <lenb@...nel.org>,
 Lorenzo Pieralisi <lpieralisi@...nel.org>, Hanjun Guo
 <guohanjun@...wei.com>, Sudeep Holla <sudeep.holla@....com>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Catalin Marinas <catalin.marinas@....com>,
 Will Deacon <will@...nel.org>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Danilo Krummrich <dakr@...nel.org>
Subject: Re: [PATCH 27/33] arm_mpam: Add mpam_msmon_read() to read monitor
 value

Hi Ben,

On 29/08/2025 16:55, Ben Horgan wrote:
> On 8/22/25 16:30, James Morse wrote:
>> Reading a monitor involves configuring what you want to monitor, and
>> reading the value. Components made up of multiple MSC may need values
>> from each MSC. MSCs may take time to configure, returning 'not ready'.
>> The maximum 'not ready' time should have been provided by firmware.
>>
>> Add mpam_msmon_read() to hide all this. If (one of) the MSC returns
>> not ready, then wait the full timeout value before trying again.

>> diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c
>> index e7e00c632512..9ce771aaf671 100644
>> --- a/drivers/resctrl/mpam_devices.c
>> +++ b/drivers/resctrl/mpam_devices.c
>> @@ -973,6 +973,228 @@ static int mpam_msc_hw_probe(struct mpam_msc *msc)

>> +static void gen_msmon_ctl_flt_vals(struct mon_read *m, u32 *ctl_val,
>> +				   u32 *flt_val)
>> +{
>> +	struct mon_cfg *ctx = m->ctx;
>> +
>> +	switch (m->type) {
>> +	case mpam_feat_msmon_csu:
>> +		*ctl_val = MSMON_CFG_CSU_CTL_TYPE_CSU;
>> +		break;
>> +	case mpam_feat_msmon_mbwu:
>> +		*ctl_val = MSMON_CFG_MBWU_CTL_TYPE_MBWU;
>> +		break;
>> +	default:
>> +		return;
>> +	}
>> +
>> +	/*
>> +	 * For CSU counters its implementation-defined what happens when not
>> +	 * filtering by partid.
>> +	 */
>> +	*ctl_val |= MSMON_CFG_x_CTL_MATCH_PARTID;
>> +
>> +	*flt_val = FIELD_PREP(MSMON_CFG_MBWU_FLT_PARTID, ctx->partid);
>> +	if (m->ctx->match_pmg) {
>> +		*ctl_val |= MSMON_CFG_x_CTL_MATCH_PMG;
>> +		*flt_val |= FIELD_PREP(MSMON_CFG_MBWU_FLT_PMG, ctx->pmg);
>> +	}

> As we are using MSMON_CFG_MBWU_FLT_{PMG,PARTID} for both CSU and MBWU
> how about changing to MSMON_CFG_x_FLT_{PMG,PARTID}?

Sure,


>> +
>> +	if (mpam_has_feature(mpam_feat_msmon_mbwu_rwbw, &m->ris->props))
>> +		*flt_val |= FIELD_PREP(MSMON_CFG_MBWU_FLT_RWBW, ctx->opts);

> This needs to be conditional on the type of the monitor being
> configured. There is an XCL bit here for CSU monitors.

Fixed ... that wasn't there last time I looked!
I may as well wire that up too...


Thanks,

James