linux-kernel - Re: [RFC PATCH V2 11/22] x86/intel_rdt: Associate pseudo-locked regions with its domain

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Date:   Mon, 19 Feb 2018 15:00:17 -0800
From:   Reinette Chatre <reinette.chatre@...el.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     fenghua.yu@...el.com, tony.luck@...el.com, gavin.hindman@...el.com,
        vikas.shivappa@...ux.intel.com, dave.hansen@...el.com,
        mingo@...hat.com, hpa@...or.com, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH V2 11/22] x86/intel_rdt: Associate pseudo-locked
 regions with its domain

Hi Thomas,

On 2/19/2018 1:19 PM, Thomas Gleixner wrote:
> On Tue, 13 Feb 2018, Reinette Chatre wrote:
> 
>> After a pseudo-locked region is locked it needs to be associated with
>> the RDT domain representing the pseudo-locked cache so that its life
>> cycle can be managed correctly.
>>
>> Only a single pseudo-locked region can exist on any cache instance so we
>> maintain a single pointer to a pseudo-locked region from each RDT
>> domain.
> 
> Why is only a single pseudo locked region possible? 

The setup of a pseudo-locked region requires the usage of wbinvd. If a
second pseudo-locked region is thus attempted it will evict the
pseudo-locked data of the first.

> 
>> Signed-off-by: Reinette Chatre <reinette.chatre@...el.com>
>> ---
>>  arch/x86/kernel/cpu/intel_rdt.h | 4 ++++
>>  1 file changed, 4 insertions(+)
>>
>> diff --git a/arch/x86/kernel/cpu/intel_rdt.h b/arch/x86/kernel/cpu/intel_rdt.h
>> index 060a0976ac00..f0e020686e99 100644
>> --- a/arch/x86/kernel/cpu/intel_rdt.h
>> +++ b/arch/x86/kernel/cpu/intel_rdt.h
>> @@ -187,6 +187,8 @@ struct mbm_state {
>>  	u64	prev_msr;
>>  };
>>  
>> +struct pseudo_lock_region;
>> +
>>  /**
>>   * struct rdt_domain - group of cpus sharing an RDT resource
>>   * @list:	all instances of this resource
>> @@ -205,6 +207,7 @@ struct mbm_state {
>>   * @ctrl_val:	array of cache or mem ctrl values (indexed by CLOSID)
>>   * @new_ctrl:	new ctrl value to be loaded
>>   * @have_new_ctrl: did user provide new_ctrl for this domain
>> + * @plr:	pseudo-locked region associated with this domain
>>   */
>>  struct rdt_domain {
>>  	struct list_head	list;
>> @@ -220,6 +223,7 @@ struct rdt_domain {
>>  	u32			*ctrl_val;
>>  	u32			new_ctrl;
>>  	bool			have_new_ctrl;
>> +	struct pseudo_lock_region	*plr;
> 
> Please keep the tabular fashion of the struct declaration intact.

Will fix.

Reinette