From: James Morse <james.morse@arm.com>
To: Reinette Chatre <reinette.chatre@intel.com>,
x86@kernel.org, linux-kernel@vger.kernel.org
Cc: Fenghua Yu <fenghua.yu@intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
H Peter Anvin <hpa@zytor.com>, Babu Moger <Babu.Moger@amd.com>,
shameerali.kolothum.thodi@huawei.com,
Jamie Iles <jamie@nuviainc.com>,
D Scott Phillips OS <scott@os.amperecomputing.com>,
lcherian@marvell.com, bobo.shaobowang@huawei.com,
tan.shaopeng@fujitsu.com
Subject: Re: [PATCH v3 07/21] x86/resctrl: Create mba_sc configuration in the rdt_domain
Date: Mon, 4 Apr 2022 17:35:45 +0100 [thread overview]
Message-ID: <f5f8166e-1831-1fa0-123c-53d3632451a8@arm.com> (raw)
In-Reply-To: <91a43681-524e-c12d-612d-259e51bde12c@intel.com>
Hi Reinette,
On 4/1/22 23:54, Reinette Chatre wrote:
> On 3/30/2022 9:43 AM, James Morse wrote:
>> On 16/03/2022 21:50, Reinette Chatre wrote:
>>> On 2/17/2022 10:20 AM, James Morse wrote:
>>>> To support resctrl's MBA software controller, the architecture must provide
>>>> a second configuration array to hold the mbps_val[] from user-space.
>>>>
>>>> This complicates the interface between the architecture specific code and
>>>> the filesystem portions of resctrl that will move to /fs/, to allow
>>>> multiple architectures to support resctrl.
>>>>
>>>> Make the filesystem parts of resctrl create an array for the mba_sc
>>>> values when is_mba_sc() is set to true. The software controller
>>>> can be changed to use this, allowing the architecture code to only
>>>> consider the values configured in hardware.
[...]
>>> Considering that no domain belonging to RDT_RESOURCE_MBA will have this array this
>>> always ends up being a null pointer de-reference.
>>
>> Ugh. I'm not sure how I managed to miss that. Thanks for debugging it!
>>
>> That loop was added to reset the array when the filesystem is mounted, as it may hold
>> stale values from a previous mount of the filesystem. Its currently done by
>> reset_all_ctrls(), but that function should really belong to the architecture code.
>>
>> Because mbm_handle_overflow() always passes a domain from the L3 to update_mba_bw(), I
>> think the cleanest thing to do is move the reset to a helper that always operates on the
>> L3 array. (and leave some breadcrumbs in the comments).
> I think this points to more than a need to reset the correct array on mount/unmount ... or
> perhaps I am not understanding this correctly?
>
> As the analysis above shows the mbps_val array only exists for rdt_domains associated
> with RDT_RESOURCE_L3 but yet mbps_val will contain the MB value provided by user space
> associated with RDT_RESOURCE_MBA.
I've finally got my head round what is going on here: I've muddled up whether mon_capable
is a resource or system property. mba_sc depends on the L3 being mon_capable, but the
configuration should be associated with MBA (wherever that is).
(basically ignore my previous reply!)
The creation of the mbps_val[] should depend on supports_mba_mbps(), which uses
is_mbm_enabled() to check whether the L3 is mon_capable. I'll check the rid too
to make it clear its only MBA that has this.
The call to allocate the domain in resctrl_online_domain() should be above the mon_capable
check. (which is still needed to avoid the work guarded by is_mbm_enabled() and friends
running for each domain).
Thanks,
James
-----------------------%<-----------------------
diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index e3c90f33baf2..ad0411eb2147 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -3345,6 +3345,14 @@ int resctrl_online_domain(struct rdt_resource *r, struct rdt_domain *d)
lockdep_assert_held(&rdtgroup_mutex);
+ if (is_mbm_enabled() && r->rid == RDT_RESOURCE_MBA) {
+ err = mba_sc_domain_allocate(r, d);
+ if (err) {
+ domain_destroy_mon_state(d);
+ return err;
+ }
+ }
+
if (!r->mon_capable)
return 0;
@@ -3352,12 +3360,6 @@ int resctrl_online_domain(struct rdt_resource *r, struct rdt_domain *d)
if (err)
return err;
- err = mba_sc_domain_allocate(r, d);
- if (err) {
- domain_destroy_mon_state(d);
- return err;
- }
-
if (is_mbm_enabled()) {
INIT_DELAYED_WORK(&d->mbm_over, mbm_handle_overflow);
mbm_setup_overflow_handler(d, MBM_OVERFLOW_INTERVAL);
-----------------------%<-----------------------
next prev parent reply other threads:[~2022-04-04 22:08 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-17 18:20 [PATCH v3 00/21] x86/resctrl: Make resctrl_arch_rmid_read() return values in bytes James Morse
2022-02-17 18:20 ` [PATCH v3 01/21] x86/resctrl: Kill off alloc_enabled James Morse
2022-03-16 21:48 ` Reinette Chatre
2022-02-17 18:20 ` [PATCH v3 02/21] x86/resctrl: Merge mon_capable and mon_enabled James Morse
2022-02-17 18:20 ` [PATCH v3 03/21] x86/resctrl: Add domain online callback for resctrl work James Morse
2022-02-17 18:20 ` [PATCH v3 04/21] x86/resctrl: Group struct rdt_hw_domain cleanup James Morse
2022-02-17 18:20 ` [PATCH v3 05/21] x86/resctrl: Add domain offline callback for resctrl work James Morse
2022-02-17 18:20 ` [PATCH v3 06/21] x86/resctrl: Remove set_mba_sc()s control array re-initialisation James Morse
2022-02-17 18:20 ` [PATCH v3 07/21] x86/resctrl: Create mba_sc configuration in the rdt_domain James Morse
2022-03-05 0:26 ` Reinette Chatre
2022-03-30 16:43 ` James Morse
2022-03-16 21:50 ` Reinette Chatre
2022-03-30 16:43 ` James Morse
2022-04-01 22:54 ` Reinette Chatre
2022-04-04 16:35 ` James Morse [this message]
2022-04-04 20:43 ` Reinette Chatre
2022-02-17 18:20 ` [PATCH v3 08/21] x86/resctrl: Switch over to the resctrl mbps_val list James Morse
2022-02-17 18:20 ` [PATCH v3 09/21] x86/resctrl: Remove architecture copy of mbps_val James Morse
2022-02-17 18:20 ` [PATCH v3 10/21] x86/resctrl: Abstract and use supports_mba_mbps() James Morse
2022-02-17 18:21 ` [PATCH v3 11/21] x86/resctrl: Allow update_mba_bw() to update controls directly James Morse
2022-02-17 18:21 ` [PATCH v3 12/21] x86/resctrl: Calculate bandwidth from the previous __mon_event_count() chunks James Morse
2022-03-05 0:27 ` Reinette Chatre
2022-03-30 16:44 ` James Morse
2022-02-17 18:21 ` [PATCH v3 13/21] x86/recstrl: Add per-rmid arch private storage for overflow and chunks James Morse
2022-03-16 21:50 ` Reinette Chatre
2022-02-17 18:21 ` [PATCH v3 14/21] x86/recstrl: Allow per-rmid arch private storage to be reset James Morse
2022-03-16 21:50 ` Reinette Chatre
2022-02-17 18:21 ` [PATCH v3 15/21] x86/resctrl: Abstract __rmid_read() James Morse
2022-03-16 21:52 ` Reinette Chatre
2022-03-30 16:44 ` James Morse
2022-02-17 18:21 ` [PATCH v3 16/21] x86/resctrl: Pass the required parameters into resctrl_arch_rmid_read() James Morse
2022-03-23 20:58 ` Rob Herring
2022-03-30 16:45 ` James Morse
2022-02-17 18:21 ` [PATCH v3 17/21] x86/resctrl: Move mbm_overflow_count() " James Morse
2022-02-17 18:21 ` [PATCH v3 18/21] x86/resctrl: Move get_corrected_mbm_count() " James Morse
2022-02-17 18:21 ` [PATCH v3 19/21] x86/resctrl: Rename and change the units of resctrl_cqm_threshold James Morse
2022-03-17 17:00 ` Reinette Chatre
2022-03-30 16:45 ` James Morse
2022-04-01 22:55 ` Reinette Chatre
2022-02-17 18:21 ` [PATCH v3 20/21] x86/resctrl: Add resctrl_rmid_realloc_limit to abstract x86's boot_cpu_data James Morse
2022-02-17 18:21 ` [PATCH v3 21/21] x86/resctrl: Make resctrl_arch_rmid_read() return values in bytes James Morse
2022-03-23 21:17 ` Rob Herring
2022-04-04 16:36 ` James Morse
2022-03-07 12:56 ` [PATCH v3 00/21] " Jamie Iles
2022-04-04 16:36 ` James Morse
2022-03-15 6:41 ` Xin Hao
2022-04-04 16:36 ` James Morse
2022-03-15 8:16 ` tan.shaopeng
2022-04-04 16:35 ` James Morse
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