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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
Subject: Re: [PATCH v1 07/20] x86/resctrl: Remove architecture copy of mbps_val
Date: Fri, 17 Sep 2021 17:57:51 +0100	[thread overview]
Message-ID: <2dd5ef98-9734-d1c4-e165-a290b5bcd1a7@arm.com> (raw)
In-Reply-To: <d52bee12-5c6c-04da-3044-7121a2c15f12@intel.com>

Hi Reinette,

On 01/09/2021 22:26, Reinette Chatre wrote:
> On 7/29/2021 3:35 PM, James Morse wrote:
>> The resctrl arch code provides a second configuration array mbps_val[]
>> for the mba socftware controller.
> 
> "mba socftware" -> "MBA software"

(fixed)

>> Since resctrl switched over to allocating and freeing its own array
>> when needed, nothing uses the arch code version.
>>
>> Remove it.

>> diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c
>> index 56b3541617b5..e864dbc6fe3d 100644
>> --- a/arch/x86/kernel/cpu/resctrl/core.c
>> +++ b/arch/x86/kernel/cpu/resctrl/core.c

>> @@ -406,12 +406,9 @@ void setup_default_ctrlval(struct rdt_resource *r, u32 *dc, u32 *dm)
>>        * Initialize the Control MSRs to having no control.
>>        * For Cache Allocation: Set all bits in cbm
>>        * For Memory Allocation: Set b/w requested to 100%
>> -     * and the bandwidth in MBps to U32_MAX
>>        */
>> -    for (i = 0; i < hw_res->num_closid; i++, dc++, dm++) {
>> +    for (i = 0; i < hw_res->num_closid; i++, dc++)
>>           *dc = r->default_ctrl;
>> -        *dm = MBA_MAX_MBPS;
>> -    }
> 
> Since this function used to reset the array to default I was expecting its callers to now
> reset the new array (more below).

dm/mbps_val? Its initialised when its allocated by mba_sc_domain_allocate() when the
filesystem is mounted, or the domain online callback is made.


>>   }
>>     static int domain_setup_ctrlval(struct rdt_resource *r, struct rdt_domain *d)

>> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> index 185f9bb992d1..297c20491549 100644
>> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> @@ -1906,7 +1906,7 @@ static int set_mba_sc(bool mba_sc)
>>       r->membw.mba_sc = mba_sc;
>>       list_for_each_entry(d, &r->domains, list) {
>>           hw_dom = resctrl_to_arch_dom(d);
>> -        setup_default_ctrlval(r, hw_dom->ctrl_val, hw_dom->mbps_val);
>> +        setup_default_ctrlval(r, hw_dom->ctrl_val);
>>       }
>>   
> 
> I am wondering why new array is not reset instead of original at this call site?

set_mba_sc() doesn't need to. During mount mba_sc is set to true in rdt_enable_ctx(),
which is before the mbps_val[] array is allocated. Once its allocated, its initialised.
While the filesystem is mounted, and domains come and go, the array is re-allocated and
re-initialised. On unmount, the array is freed when the schemata list is destroyed.

I think moving the allocation/free into set_mba_sc() will make this clearer.

> oh ... I
> see it is removed in following patch BUT it mentions that it is ok because
> reset_all_ctrls() does similar reset ... but it does not seem to do so for mbps_val.

That is about the ctrl_val[] array. The reset_all_ctrls() call should reset the hardware
that the arch code looks after. After these changes the mbps_val[] array is a resctrl
filesystem thing that the arch code doesn't need to know anything about.


Thanks,

James

  reply	other threads:[~2021-09-17 16:58 UTC|newest]

Thread overview: 50+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-29 22:35 [PATCH v1 00/20] x86/resctrl: Make resctrl_arch_rmid_read() return values in bytes James Morse
2021-07-29 22:35 ` [PATCH v1 01/20] x86/resctrl: Kill off alloc_enabled James Morse
2021-08-11 12:12   ` Jamie Iles
2021-09-01 21:18   ` Reinette Chatre
2021-07-29 22:35 ` [PATCH v1 02/20] x86/resctrl: Merge mon_capable and mon_enabled James Morse
2021-08-11 12:15   ` Jamie Iles
2021-08-11 15:16     ` James Morse
2021-07-29 22:35 ` [PATCH v1 03/20] x86/resctrl: Add domain online callback for resctrl work James Morse
2021-09-01 21:19   ` Reinette Chatre
2021-09-17 16:57     ` James Morse
2021-07-29 22:35 ` [PATCH v1 04/20] x86/resctrl: Add domain offline " James Morse
2021-08-11 16:10   ` Jamie Iles
2021-09-01 21:21   ` Reinette Chatre
2021-07-29 22:35 ` [PATCH v1 05/20] x86/resctrl: Create mba_sc configuration in the rdt_domain James Morse
2021-08-11 16:32   ` Jamie Iles
2021-08-31 16:24     ` James Morse
2021-09-01 21:22   ` Reinette Chatre
2021-09-17 16:57     ` James Morse
2021-07-29 22:35 ` [PATCH v1 06/20] x86/resctrl: Switch over to the resctrl mbps_val list James Morse
2021-09-01 21:25   ` Reinette Chatre
2021-09-17 16:57     ` James Morse
2021-09-17 18:20       ` Reinette Chatre
2021-10-01 16:02         ` James Morse
2021-07-29 22:35 ` [PATCH v1 07/20] x86/resctrl: Remove architecture copy of mbps_val James Morse
2021-09-01 21:26   ` Reinette Chatre
2021-09-17 16:57     ` James Morse [this message]
2021-07-29 22:35 ` [PATCH v1 08/20] x86/resctrl: Remove set_mba_sc()s control array re-initialisation James Morse
2021-07-29 22:35 ` [PATCH v1 09/20] x86/resctrl: Abstract and use supports_mba_mbps() James Morse
2021-09-01 21:27   ` Reinette Chatre
2021-09-17 16:57     ` James Morse
2021-09-24  6:23   ` tan.shaopeng
2021-10-01 16:01     ` James Morse
2021-07-29 22:36 ` [PATCH v1 10/20] x86/resctrl: Allow update_mba_bw() to update controls directly James Morse
2021-09-01 21:28   ` Reinette Chatre
2021-07-29 22:36 ` [PATCH v1 11/20] x86/resctrl: Calculate bandwidth from the total bytes counter James Morse
2021-09-01 21:31   ` Reinette Chatre
2021-09-17 16:58     ` James Morse
2021-07-29 22:36 ` [PATCH v1 12/20] x86/recstrl: Add per-rmid arch private storage for overflow and chunks James Morse
2021-08-11 17:14   ` Jamie Iles
2021-08-31 16:25     ` James Morse
2021-07-29 22:36 ` [PATCH v1 13/20] x86/recstrl: Allow per-rmid arch private storage to be reset James Morse
2021-09-24  6:34   ` tan.shaopeng
2021-10-01 16:01     ` James Morse
2021-07-29 22:36 ` [PATCH v1 14/20] x86/resctrl: Abstract __rmid_read() James Morse
2021-07-29 22:36 ` [PATCH v1 15/20] x86/resctrl: Pass the required parameters into resctrl_arch_rmid_read() James Morse
2021-07-29 22:36 ` [PATCH v1 16/20] x86/resctrl: Move mbm_overflow_count() " James Morse
2021-07-29 22:36 ` [PATCH v1 17/20] x86/resctrl: Move get_corrected_mbm_count() " James Morse
2021-07-29 22:36 ` [PATCH v1 18/20] x86/resctrl: Rename and change the units of resctrl_cqm_threshold James Morse
2021-07-29 22:36 ` [PATCH v1 19/20] x86/resctrl: Add resctrl_rmid_realloc_limit to abstract x86's boot_cpu_data James Morse
2021-07-29 22:36 ` [PATCH v1 20/20] x86/resctrl: Make resctrl_arch_rmid_read() return values in bytes James Morse

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