linux-kernel - Re: [PATCH v4 18/24] x86/resctrl: Make ctrlval arrays the same size

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Message-ID: <46b42971-724c-c585-efec-c824838d7434@arm.com>
Date:   Thu, 17 Jun 2021 18:03:10 +0100
From:   James Morse <james.morse@....com>
To:     Reinette Chatre <reinette.chatre@...el.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Cc:     Fenghua Yu <fenghua.yu@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        H Peter Anvin <hpa@...or.com>,
        Babu Moger <Babu.Moger@....com>,
        shameerali.kolothum.thodi@...wei.com,
        Jamie Iles <jamie@...iainc.com>,
        D Scott Phillips OS <scott@...amperecomputing.com>,
        lcherian@...vell.com
Subject: Re: [PATCH v4 18/24] x86/resctrl: Make ctrlval arrays the same size

Hi Reinette,

On 15/06/2021 19:09, Reinette Chatre wrote:
> On 6/14/2021 1:09 PM, James Morse wrote:
>> The CODE and DATA resources report a num_closid that is half the
>> actual size supported by the hardware. This behaviour is visible
>> to user-space when CDP is enabled.
>> The CODE and DATA resources have their own ctrlval arrays which are half
>> the size of the underlying hardware because num_closid was already
>> adjusted. One holds the odd configurations values, the other even.
>>
>> Before the CDP resources can be merged, the 'half the closids'
>> behaviour needs to be implemented by schemata_list_create(), but
>> this causes the ctrl_val[] array to be full sized.
>>
>> Remove the logic from the architecture specific rdt_get_cdp_config()
>> setup, and add it to schemata_list_create(). Functions that
>> walk take num_closid directly from struct rdt_hw_resource also
> 
> This is unclear to me ... "Functions that walk ..." seems like it is missing to describe
> what they are walking.

Yup, I'm missing at least a word here! Fixed as:
| functions that walk all the configurations, such as domain_setup_ctrlval() and
| reset_all_ctrls() , take the num_closids directly from...


>> have to halve num_closid as only the lower half of each array is
>> in use. domain_setup_ctrlval() and reset_all_ctrls() both copy
>> struct rdt_hw_resource's num_closid to a struct msr_param. Correct
>> the value here. This is temporary as a subsequent patch will merge
>> the all three ctrl_val[] arrays such that when CDP is in use, the
> 
> the all three -> all three ?

Yes. Thanks!

(I've never managed to spot things like this in text I wrote)


Thanks,

James