linux-kernel - Re: [PATCH v4 13/21] x86/resctrl: Add per-rmid arch private storage for overflow and chunks

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Message-ID: <3cefbfff-1beb-bf16-f9b0-ebb526d70500@intel.com>
Date:   Wed, 18 May 2022 09:06:47 -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>,
        D Scott Phillips OS <scott@...amperecomputing.com>,
        <lcherian@...vell.com>, <bobo.shaobowang@...wei.com>,
        <tan.shaopeng@...itsu.com>, Jamie Iles <quic_jiles@...cinc.com>,
        Cristian Marussi <cristian.marussi@....com>,
        "Xin Hao" <xhao@...ux.alibaba.com>, <xingxin.hx@...nanolis.org>,
        <baolin.wang@...ux.alibaba.com>
Subject: Re: [PATCH v4 13/21] x86/resctrl: Add per-rmid arch private storage
 for overflow and chunks

Hi James,

On 4/12/2022 5:44 AM, James Morse wrote:
> A renamed __rmid_read() is intended as the function that an
> architecture agnostic resctrl filesystem driver can use to
> read a value in bytes from a counter. Currently the function returns
> the MBM values in chunks directly from hardware. For bandwidth
> counters the resctrl filesystem uses this to calculate the number of
> bytes ever seen.
> 
> MPAM's scaling of counters can be changed at runtime, reducing the
> resolution but increasing the range. When this is changed the prev_msr
> values need to be converted by the architecture code.
> 
> Add an array for per-rmid private storage. The prev_msr and chunks
> values will move here to allow resctrl_arch_rmid_read() to always
> return the number of bytes read by this counter without assistance
> from the filesystem. The values are moved in later patches when
> the overflow and correction calls are moved into __rmid_read().
> 
> Reviewed-by: Jamie Iles <quic_jiles@...cinc.com>
> Tested-by: Xin Hao <xhao@...ux.alibaba.com>
> Reviewed-by: Shaopeng Tan <tan.shaopeng@...itsu.com>
> Tested-by: Shaopeng Tan <tan.shaopeng@...itsu.com>
> Tested-by: Cristian Marussi <cristian.marussi@....com>
> Signed-off-by: James Morse <james.morse@....com>
> ----
> Changes since v2:
>  * Capitalisation
>  * Use __rmid_read() as this patch is earlier in the series.
>  * kfree() one array in arch_domain_mbm_alloc() when allocating the other
>    fails, instead of relying on domain_free().
>  * Remove the documentation that domain_free() has to be called to cleanup
>    if this call fails.
> ---

Please ensure that this list of changes are always preceded by "---". In this
patch and patch 21/21 that uses "----" the list of changes ends up as part of
the changelog when using b4 to pick up patches.

Reinette