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

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Date:   Tue, 15 Jun 2021 11:09:11 -0700
From:   Reinette Chatre <reinette.chatre@...el.com>
To:     James Morse <james.morse@....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 James,

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.

> 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 ?

Reinette