linux-kernel - Re: [PATCH v3] x86/resctrl: Preserve CDP enable over cpuhp

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Date:   Wed, 15 Apr 2020 08:57:34 -0700
From:   Reinette Chatre <reinette.chatre@...el.com>
To:     James Morse <james.morse@....com>, x86@...nel.org,
        linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>
Cc:     Fenghua Yu <fenghua.yu@...el.com>, Ingo Molnar <mingo@...hat.com>,
        "H . Peter Anvin" <hpa@...or.com>, Babu Moger <Babu.Moger@....com>
Subject: Re: [PATCH v3] x86/resctrl: Preserve CDP enable over cpuhp

Hi Thomas and Borislav,

Could you please consider this patch for inclusion as a fix for v5.7?

Thank you

Reinette

On 2/24/2020 10:23 AM, Reinette Chatre wrote:
> Hi James,
> 
> On 2/21/2020 8:21 AM, James Morse wrote:
>> Resctrl assumes that all CPUs are online when the filesystem is
>> mounted, and that CPUs remember their CDP-enabled state over CPU
>> hotplug.
>>
>> This goes wrong when resctrl's CDP-enabled state changes while all
>> the CPUs in a domain are offline.
>>
>> When a domain comes online, enable (or disable!) CDP to match resctrl's
>> current setting.
>>
>> Fixes: 5ff193fbde20 ("x86/intel_rdt: Add basic resctrl filesystem support")
>> Suggested-by: Reinette Chatre <reinette.chatre@...el.com>
>> Signed-off-by: James Morse <james.morse@....com>
>> ---
>>  arch/x86/kernel/cpu/resctrl/core.c     |  2 ++
>>  arch/x86/kernel/cpu/resctrl/internal.h |  1 +
>>  arch/x86/kernel/cpu/resctrl/rdtgroup.c | 13 +++++++++++++
>>  3 files changed, 16 insertions(+)
>>
>> diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c
>> index 89049b343c7a..d8cc5223b7ce 100644
>> --- a/arch/x86/kernel/cpu/resctrl/core.c
>> +++ b/arch/x86/kernel/cpu/resctrl/core.c
>> @@ -578,6 +578,8 @@ static void domain_add_cpu(int cpu, struct rdt_resource *r)
>>  	d->id = id;
>>  	cpumask_set_cpu(cpu, &d->cpu_mask);
>>  
>> +	rdt_domain_reconfigure_cdp(r);
>> +
>>  	if (r->alloc_capable && domain_setup_ctrlval(r, d)) {
>>  		kfree(d);
>>  		return;
>> diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
>> index 181c992f448c..3dd13f3a8b23 100644
>> --- a/arch/x86/kernel/cpu/resctrl/internal.h
>> +++ b/arch/x86/kernel/cpu/resctrl/internal.h
>> @@ -601,5 +601,6 @@ bool has_busy_rmid(struct rdt_resource *r, struct rdt_domain *d);
>>  void __check_limbo(struct rdt_domain *d, bool force_free);
>>  bool cbm_validate_intel(char *buf, u32 *data, struct rdt_resource *r);
>>  bool cbm_validate_amd(char *buf, u32 *data, struct rdt_resource *r);
>> +void rdt_domain_reconfigure_cdp(struct rdt_resource *r);
>>  
>>  #endif /* _ASM_X86_RESCTRL_INTERNAL_H */
>> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> index 064e9ef44cd6..1c78908ef395 100644
>> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> @@ -1859,6 +1859,19 @@ static int set_cache_qos_cfg(int level, bool enable)
>>  	return 0;
>>  }
>>  
>> +/* Restore the qos cfg state when a domain comes online */
>> +void rdt_domain_reconfigure_cdp(struct rdt_resource *r)
>> +{
>> +	if (!r->alloc_capable)
>> +		return;
>> +
>> +	if (r == &rdt_resources_all[RDT_RESOURCE_L2DATA])
>> +		l2_qos_cfg_update(&r->alloc_enabled);
>> +
>> +	if (r == &rdt_resources_all[RDT_RESOURCE_L3DATA])
>> +		l3_qos_cfg_update(&r->alloc_enabled);
>> +}
>> +
>>  /*
>>   * Enable or disable the MBA software controller
>>   * which helps user specify bandwidth in MBps.
>>
> 
> As mentioned in my response to v2 the lockdep annotation that formed
> part of this fix is welcome. It is not clear to me if you will be
> submitting again with the annotation added back. Since it is not
> required for this fix I will add my tag here and you could include it if
> you do decide to resubmit.
> 
> Thank you
> 
> Reviewed-by: Reinette Chatre <reinette.chatre@...el.com>
> 
> Reinette
>