Re: [PATCH v2 34/45] arm_mpam: resctrl: Add resctrl_arch_rmid_read() and resctrl_arch_reset_rmid()

Jonathan Cameron
2026-01-06T14:43:51Z

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

> From: James Morse <james.morse@arm.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@arm.com>
> Signed-off-by: Ben Horgan <ben.horgan@arm.com>
Trivial stuff only.
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.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);
> +}