linux-kernel - Re: [PATCH v2 34/45] arm_mpam: resctrl: Add resctrl_arch_rmid_read() and resctrl_arch_reset

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Message-ID: <20260106144346.000053b0@huawei.com>
Date: Tue, 6 Jan 2026 14:43:46 +0000
From: Jonathan Cameron <jonathan.cameron@...wei.com>
To: Ben Horgan <ben.horgan@....com>
CC: <amitsinght@...vell.com>, <baisheng.gao@...soc.com>,
	<baolin.wang@...ux.alibaba.com>, <carl@...amperecomputing.com>,
	<dave.martin@....com>, <david@...nel.org>, <dfustini@...libre.com>,
	<fenghuay@...dia.com>, <gshan@...hat.com>, <james.morse@....com>,
	<kobak@...dia.com>, <lcherian@...vell.com>,
	<linux-arm-kernel@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
	<peternewman@...gle.com>, <punit.agrawal@....qualcomm.com>,
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	<joey.gouly@....com>, <suzuki.poulose@....com>, <kvmarm@...ts.linux.dev>
Subject: Re: [PATCH v2 34/45] arm_mpam: resctrl: Add
 resctrl_arch_rmid_read() and resctrl_arch_reset_rmid()

On Fri, 19 Dec 2025 18:11:36 +0000
Ben Horgan <ben.horgan@....com> wrote:

> From: James Morse <james.morse@....com>
> 
> resctrl uses resctrl_arch_rmid_read() to read counters. CDP emulation means
> the counter may need reading in three different ways. The same goes for
> reset.
> 
> The helpers behind the resctrl_arch_ functions will be re-used for the ABMC
> equivalent functions.
> 
> Add the rounding helper for checking monitor values while we're here.
> 
> Signed-off-by: James Morse <james.morse@....com>
> Signed-off-by: Ben Horgan <ben.horgan@....com>
Trivial stuff only.
Reviewed-by: Jonathan Cameron <jonathan.cameron@...wei.com>

> ---
> Changes since rfc:
> cfg intialisation style
> code flow at end of read_mon_cdp_safe()
> ---
>  drivers/resctrl/mpam_resctrl.c | 159 +++++++++++++++++++++++++++++++++
>  include/linux/arm_mpam.h       |   5 ++
>  2 files changed, 164 insertions(+)
> 
> diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
> index 638c84cdcfb6..8a1263986145 100644
> --- a/drivers/resctrl/mpam_resctrl.c
> +++ b/drivers/resctrl/mpam_resctrl.c
> @@ -354,6 +354,165 @@ void resctrl_arch_mon_ctx_free(struct rdt_resource *r,
>  	resctrl_arch_mon_ctx_free_no_wait(evtid, mon_idx);
>  }
>  
> +static int
Whilst I don't really care, this does seem inconsistent from other functions
static int __read_mon(...
probably for consistent looking code.

> +__read_mon(struct mpam_resctrl_mon *mon, struct mpam_component *mon_comp,
> +	   enum mpam_device_features mon_type,
> +	   int mon_idx,
> +	   enum resctrl_conf_type cdp_type, u32 closid, u32 rmid, u64 *val)
> +{
> +	struct mon_cfg cfg;
> +
> +	if (!mpam_is_enabled())
> +		return -EINVAL;
> +
> +	/* Shift closid to account for CDP */
> +	closid = resctrl_get_config_index(closid, cdp_type);
> +
> +	if (mon_idx == USE_PRE_ALLOCATED) {
> +		int mbwu_idx = resctrl_arch_rmid_idx_encode(closid, rmid);
> +
> +		mon_idx = mon->mbwu_idx_to_mon[mbwu_idx];
> +		if (mon_idx == -1) {
> +			if (mpam_resctrl_abmc_enabled()) {
> +				/* Report Unassigned */
> +				return -ENOENT;
> +			}
> +			/* Report Unavailable */
> +			return -EINVAL;
> +		}
> +	}
> +
> +	if (irqs_disabled()) {
> +		/* Check if we can access this domain without an IPI */
> +		return -EIO;
> +	}
> +
> +	cfg = (struct mon_cfg) {
> +		.mon = mon_idx,
> +		.match_pmg = true,
> +		.partid = closid,
> +		.pmg = rmid,
> +	};
> +
> +	return mpam_msmon_read(mon_comp, &cfg, mon_type, val);
> +}

> +/* MBWU when not in ABMC mode, and CSU counters. */
> +int resctrl_arch_rmid_read(struct rdt_resource	*r, struct rdt_mon_domain *d,

Odd tab before *r.

> +			   u32 closid, u32 rmid, enum resctrl_event_id eventid,
> +			   u64 *val, void *arch_mon_ctx)
> +{
> +	struct mpam_resctrl_dom *l3_dom;
> +	struct mpam_component *mon_comp;
> +	u32 mon_idx = *(u32 *)arch_mon_ctx;
> +	enum mpam_device_features mon_type;
> +	struct mpam_resctrl_mon *mon = &mpam_resctrl_counters[eventid];
> +
> +	resctrl_arch_rmid_read_context_check();
> +
> +	if (eventid >= QOS_NUM_EVENTS || !mon->class)
> +		return -EINVAL;
> +
> +	l3_dom = container_of(d, struct mpam_resctrl_dom, resctrl_mon_dom);
> +	mon_comp = l3_dom->mon_comp[eventid];
> +
> +	switch (eventid) {
> +	case QOS_L3_OCCUP_EVENT_ID:
> +		mon_type = mpam_feat_msmon_csu;
> +		break;
> +	case QOS_L3_MBM_LOCAL_EVENT_ID:
> +	case QOS_L3_MBM_TOTAL_EVENT_ID:
> +		mon_type = mpam_feat_msmon_mbwu;
> +		break;
> +	default:
> +		return -EINVAL;
> +	}
> +
> +	return read_mon_cdp_safe(mon, mon_comp, mon_type, mon_idx,
> +				 closid, rmid, val);
> +}