linux-kernel - Re: [PATCH v2 23/29] arm_mpam: Add mpam_msmon

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Message-ID: <ca0d63a6-0325-4a1d-8b80-6bdc41034fa8@arm.com>
Date: Mon, 6 Oct 2025 17:00:49 +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
Cc: 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>, 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>,
 Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Danilo Krummrich <dakr@...nel.org>
Subject: Re: [PATCH v2 23/29] arm_mpam: Add mpam_msmon_read() to read monitor
 value

Hi Ben,

On 12/09/2025 16:08, Ben Horgan wrote:
> On 9/11/25 16:46, Ben Horgan wrote:
>> On 9/10/25 21:43, 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 cf190f896de1..1543c33c5d6a 100644
>>> --- a/drivers/resctrl/mpam_devices.c
>>> +++ b/drivers/resctrl/mpam_devices.c
>>> +
>>> +static void gen_msmon_ctl_flt_vals(struct mon_read *m, u32 *ctl_val,
>>> +				   u32 *flt_val)
>>> +{
>>> +	struct mon_cfg *ctx = m->ctx;
>>> +
>>> +	/*
>>> +	 * 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_x_FLT_PARTID, ctx->partid);
>>> +	if (m->ctx->match_pmg) {
>>> +		*ctl_val |= MSMON_CFG_x_CTL_MATCH_PMG;
>>> +		*flt_val |= FIELD_PREP(MSMON_CFG_x_FLT_PMG, ctx->pmg);
>>> +	}
>>> +
>>> +	switch (m->type) {
>>> +	case mpam_feat_msmon_csu:
>>> +		*ctl_val = MSMON_CFG_CSU_CTL_TYPE_CSU;
>>> +
>>> +		if (mpam_has_feature(mpam_feat_msmon_csu_xcl, &m->ris->props))
>>> +			*flt_val |= FIELD_PREP(MSMON_CFG_CSU_FLT_XCL,
>>> +					       ctx->csu_exclude_clean);
>>> +
>>> +		break;
>>> +	case mpam_feat_msmon_mbwu:
>>> +		*ctl_val = MSMON_CFG_MBWU_CTL_TYPE_MBWU;
> 
> As you mentioned offline, this zeroes the other bits in *ctl_val.

Yes - a bug introduced during a late night, I've fixed this up.


Thanks,

James