linux-kernel - Re: [PATCH v2 18/45] arm_mpam: resctrl: Implement resctrl_arch_reset_all

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Message-ID: <20260105175154.00002041@huawei.com>
Date: Mon, 5 Jan 2026 17:51:54 +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>,
	<quic_jiles@...cinc.com>, <reinette.chatre@...el.com>,
	<rohit.mathew@....com>, <scott@...amperecomputing.com>,
	<sdonthineni@...dia.com>, <tan.shaopeng@...itsu.com>,
	<xhao@...ux.alibaba.com>, <catalin.marinas@....com>, <will@...nel.org>,
	<corbet@....net>, <maz@...nel.org>, <oupton@...nel.org>,
	<joey.gouly@....com>, <suzuki.poulose@....com>, <kvmarm@...ts.linux.dev>
Subject: Re: [PATCH v2 18/45] arm_mpam: resctrl: Implement
 resctrl_arch_reset_all_ctrls()

On Fri, 19 Dec 2025 18:11:20 +0000
Ben Horgan <ben.horgan@....com> wrote:

> From: James Morse <james.morse@....com>
> 
> We already have a helper for resetting an mpam class and component.  Hook
> it up to resctrl_arch_reset_all_ctrls() and the domain offline path.
> 
> Signed-off-by: James Morse <james.morse@....com>
> Signed-off-by: Ben Horgan <ben.horgan@....com>
I left all the context as my one comment on this is I don't see a reason
to expose mpam_reset_class()  Only the _locked() variant ever seems to be
used outside of mpam_devices.c

> ---
>  drivers/resctrl/mpam_devices.c  |  6 +++---
>  drivers/resctrl/mpam_internal.h |  7 +++++++
>  drivers/resctrl/mpam_resctrl.c  | 15 +++++++++++++++
>  3 files changed, 25 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c
> index 303aacfcb9d6..4f5d908d02a9 100644
> --- a/drivers/resctrl/mpam_devices.c
> +++ b/drivers/resctrl/mpam_devices.c
> @@ -2544,7 +2544,7 @@ static void mpam_enable_once(void)
>  	       mpam_partid_max + 1, mpam_pmg_max + 1);
>  }
>  
> -static void mpam_reset_component_locked(struct mpam_component *comp)
> +void mpam_reset_component_locked(struct mpam_component *comp)
>  {
>  	struct mpam_vmsc *vmsc;
>  
> @@ -2568,7 +2568,7 @@ static void mpam_reset_component_locked(struct mpam_component *comp)
>  	}
>  }
>  
> -static void mpam_reset_class_locked(struct mpam_class *class)
> +void mpam_reset_class_locked(struct mpam_class *class)
>  {
>  	struct mpam_component *comp;
>  
> @@ -2580,7 +2580,7 @@ static void mpam_reset_class_locked(struct mpam_class *class)
>  		mpam_reset_component_locked(comp);
>  }
>  
> -static void mpam_reset_class(struct mpam_class *class)
> +void mpam_reset_class(struct mpam_class *class)
>  {
>  	cpus_read_lock();
>  	mpam_reset_class_locked(class);
> diff --git a/drivers/resctrl/mpam_internal.h b/drivers/resctrl/mpam_internal.h
> index 554e4887ba81..b9a739abb101 100644
> --- a/drivers/resctrl/mpam_internal.h
> +++ b/drivers/resctrl/mpam_internal.h
> @@ -389,6 +389,13 @@ extern u8 mpam_pmg_max;
>  void mpam_enable(struct work_struct *work);
>  void mpam_disable(struct work_struct *work);
>  
> +/* Reset all the RIS in a class, optionally while holding cpus_read_lock() */
> +void mpam_reset_class_locked(struct mpam_class *class);
> +void mpam_reset_class(struct mpam_class *class);

Not clear from this patch why we need to expose mpam_reset_class()

> +
> +/* Reset all the RIS in a component under cpus_read_lock() */
> +void mpam_reset_component_locked(struct mpam_component *comp);
> +
>  int mpam_apply_config(struct mpam_component *comp, u16 partid,
>  		      struct mpam_config *cfg);
>  
> diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
> index bc4f1c80eab5..d32e87002457 100644
> --- a/drivers/resctrl/mpam_resctrl.c
> +++ b/drivers/resctrl/mpam_resctrl.c
> @@ -167,6 +167,19 @@ static int mpam_resctrl_pick_domain_id(int cpu, struct mpam_component *comp)
>  	return comp->comp_id;
>  }
>  
> +void resctrl_arch_reset_all_ctrls(struct rdt_resource *r)
> +{
> +	struct mpam_resctrl_res *res;
> +
> +	lockdep_assert_cpus_held();
> +
> +	if (!mpam_is_enabled())
> +		return;
> +
> +	res = container_of(r, struct mpam_resctrl_res, resctrl_res);
> +	mpam_reset_class_locked(res->class);
> +}
> +
>  static void mpam_resctrl_domain_hdr_init(int cpu, struct mpam_component *comp,
>  					 struct rdt_domain_hdr *hdr)
>  {
> @@ -353,6 +366,8 @@ void mpam_resctrl_offline_cpu(unsigned int cpu)
>  
>  		ctrl_dom_empty = true;
>  		if (exposed_alloc_capable) {
> +			mpam_reset_component_locked(dom->ctrl_comp);
> +
>  			ctrl_d = &dom->resctrl_ctrl_dom;
>  			ctrl_dom_empty = mpam_resctrl_offline_domain_hdr(cpu, &ctrl_d->hdr);
>  			if (ctrl_dom_empty)