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Message-ID: <e2b9bcd1-4b5d-4eb9-8e3c-604a4c5cafe8@intel.com>
Date: Fri, 16 Aug 2024 14:41:41 -0700
From: Reinette Chatre <reinette.chatre@...el.com>
To: Babu Moger <babu.moger@....com>, <corbet@....net>, <fenghua.yu@...el.com>,
<tglx@...utronix.de>, <mingo@...hat.com>, <bp@...en8.de>,
<dave.hansen@...ux.intel.com>
CC: <x86@...nel.org>, <hpa@...or.com>, <paulmck@...nel.org>,
<rdunlap@...radead.org>, <tj@...nel.org>, <peterz@...radead.org>,
<yanjiewtw@...il.com>, <kim.phillips@....com>, <lukas.bulwahn@...il.com>,
<seanjc@...gle.com>, <jmattson@...gle.com>, <leitao@...ian.org>,
<jpoimboe@...nel.org>, <rick.p.edgecombe@...el.com>,
<kirill.shutemov@...ux.intel.com>, <jithu.joseph@...el.com>,
<kai.huang@...el.com>, <kan.liang@...ux.intel.com>,
<daniel.sneddon@...ux.intel.com>, <pbonzini@...hat.com>,
<sandipan.das@....com>, <ilpo.jarvinen@...ux.intel.com>,
<peternewman@...gle.com>, <maciej.wieczor-retman@...el.com>,
<linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
<eranian@...gle.com>, <james.morse@....com>
Subject: Re: [PATCH v6 16/22] x86/resctrl: Add the interface to unassign a MBM
counter
Hi Babu,
On 8/6/24 3:00 PM, Babu Moger wrote:
> The ABMC feature provides an option to the user to assign a hardware
This is about resctrl fs so "The ABMC feature" -> "mbm_cntr_assign mode"
(please check whole series).
> counter to an RMID and monitor the bandwidth as long as it is assigned.
> The assigned RMID will be tracked by the hardware until the user unassigns
> it manually.
>
> Hardware provides only limited number of counters. If the system runs out
> of assignable counters, kernel will display an error when a new assignment
> is requested. Users need to unassign a already assigned counter to make
> space for new assignment.
>
> Provide the interface to unassign the counter ids from the group. Free the
> counter if it is not assigned in any of the domains.
>
> The feature details are documented in the APM listed below [1].
> [1] AMD64 Architecture Programmer's Manual Volume 2: System Programming
> Publication # 24593 Revision 3.41 section 19.3.3.3 Assignable Bandwidth
> Monitoring (ABMC).
>
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=206537
> Signed-off-by: Babu Moger <babu.moger@....com>
> ---
> v6: Removed mbm_cntr_free from this patch.
> Added counter test in all the domains and free if it is not assigned to
> any domains.
>
> v5: Few name changes to match cntr_id.
> Changed the function names to
> rdtgroup_unassign_cntr
> More comments on commit log.
>
> v4: Added domain specific unassign feature.
> Few name changes.
>
> v3: Removed the static from the prototype of rdtgroup_unassign_abmc.
> The function is not called directly from user anymore. These
> changes are related to global assignment interface.
>
> v2: No changes.
> ---
> arch/x86/kernel/cpu/resctrl/internal.h | 2 +
> arch/x86/kernel/cpu/resctrl/rdtgroup.c | 52 ++++++++++++++++++++++++++
> 2 files changed, 54 insertions(+)
>
> diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
> index 4e8109dee174..cc832955b787 100644
> --- a/arch/x86/kernel/cpu/resctrl/internal.h
> +++ b/arch/x86/kernel/cpu/resctrl/internal.h
> @@ -689,6 +689,8 @@ int resctrl_arch_assign_cntr(struct rdt_mon_domain *d, enum resctrl_event_id evt
> u32 rmid, u32 cntr_id, u32 closid, bool assign);
> int rdtgroup_assign_cntr(struct rdtgroup *rdtgrp, enum resctrl_event_id evtid);
> int rdtgroup_alloc_cntr(struct rdtgroup *rdtgrp, int index);
> +int rdtgroup_unassign_cntr(struct rdtgroup *rdtgrp, enum resctrl_event_id evtid);
> +void rdtgroup_free_cntr(struct rdt_resource *r, struct rdtgroup *rdtgrp, int index);
> void rdt_staged_configs_clear(void);
> bool closid_allocated(unsigned int closid);
> int resctrl_find_cleanest_closid(void);
> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> index 1ee91a7293a8..0c2215dbd497 100644
> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> @@ -1961,6 +1961,58 @@ int rdtgroup_assign_cntr(struct rdtgroup *rdtgrp, enum resctrl_event_id evtid)
> return 0;
> }
>
> +static int rdtgroup_mbm_cntr_test(struct rdt_resource *r, u32 cntr_id)
Could "test" be replaced with something more specific about what is tested?
for example, "rdtgroup_mbm_cntr_is_assigned()" or something better? The function
looks like a good candidate for returning a bool.
Is this function needed though? (more below)
> +{
> + struct rdt_mon_domain *d;
> +
> + list_for_each_entry(d, &r->mon_domains, hdr.list)
> + if (test_bit(cntr_id, d->mbm_cntr_map))
> + return 1;
> +
> + return 0;
> +}
> +
> +/* Free the counter id after the event is unassigned */
> +void rdtgroup_free_cntr(struct rdt_resource *r, struct rdtgroup *rdtgrp,
> + int index)
> +{
> + /* Update the counter bitmap */
> + if (!rdtgroup_mbm_cntr_test(r, rdtgrp->mon.cntr_id[index])) {
> + mbm_cntr_free(rdtgrp->mon.cntr_id[index]);
> + rdtgrp->mon.cntr_id[index] = MON_CNTR_UNSET;
> + }
> +}
> +
> +/*
> + * Unassign a hardware counter from the group and update all the domains
> + * in the group.
> + */
> +int rdtgroup_unassign_cntr(struct rdtgroup *rdtgrp, enum resctrl_event_id evtid)
> +{
> + struct rdt_resource *r = &rdt_resources_all[RDT_RESOURCE_L3].r_resctrl;
> + struct rdt_mon_domain *d;
> + int index;
> +
> + index = mon_event_config_index_get(evtid);
> + if (index == INVALID_CONFIG_INDEX)
> + return -EINVAL;
> +
> + if (rdtgrp->mon.cntr_id[index] != MON_CNTR_UNSET) {
> + list_for_each_entry(d, &r->mon_domains, hdr.list) {
> + resctrl_arch_assign_cntr(d, evtid, rdtgrp->mon.rmid,
> + rdtgrp->mon.cntr_id[index],
> + rdtgrp->closid, false);
> + clear_bit(rdtgrp->mon.cntr_id[index],
> + d->mbm_cntr_map);
> + }
> +
> + /* Free the counter at group level */
> + rdtgroup_free_cntr(r, rdtgrp, index);
rdtgroup_free_cntr() is called right after the counter has been unassigned
from all domains. Will rdtgroup_mbm_cntr_test() thus not always return 0?
It seems unnecessary to have rdtgroup_mbm_cntr_test() and considering that,
rdtgroup_free_cntr() can just be open coded here?
> + }
> +
> + return 0;
> +}
> +
> /* rdtgroup information files for one cache resource. */
> static struct rftype res_common_files[] = {
> {
Reinette
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