linux-kernel - Re: [PATCH 31/33] arm_mpam: Add helper to reset saved mbwu state

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Message-ID: <67a36e6d-daab-479f-a1c5-3b2444a71d7c@redhat.com>
Date: Mon, 10 Nov 2025 09:18:14 +1000
From: Gavin Shan <gshan@...hat.com>
To: Ben Horgan <ben.horgan@....com>, james.morse@....com
Cc: amitsinght@...vell.com, baisheng.gao@...soc.com,
 baolin.wang@...ux.alibaba.com, bobo.shaobowang@...wei.com,
 carl@...amperecomputing.com, catalin.marinas@....com, dakr@...nel.org,
 dave.martin@....com, david@...hat.com, dfustini@...libre.com,
 fenghuay@...dia.com, gregkh@...uxfoundation.org, guohanjun@...wei.com,
 jeremy.linton@....com, jonathan.cameron@...wei.com, kobak@...dia.com,
 lcherian@...vell.com, lenb@...nel.org, linux-acpi@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
 lpieralisi@...nel.org, peternewman@...gle.com, quic_jiles@...cinc.com,
 rafael@...nel.org, robh@...nel.org, rohit.mathew@....com,
 scott@...amperecomputing.com, sdonthineni@...dia.com, sudeep.holla@....com,
 tan.shaopeng@...itsu.com, will@...nel.org, xhao@...ux.alibaba.com,
 Fenghua Yu <fenghuay@...ia.com>
Subject: Re: [PATCH 31/33] arm_mpam: Add helper to reset saved mbwu state

On 11/7/25 10:34 PM, Ben Horgan wrote:
> From: James Morse <james.morse@....com>
> 
> resctrl expects to reset the bandwidth counters when the filesystem
> is mounted.
> 
> To allow this, add a helper that clears the saved mbwu state. Instead
> of cross calling to each CPU that can access the component MSC to
> write to the counter, set a flag that causes it to be zero'd on the
> the next read. This is easily done by forcing a configuration update.
> 
> Signed-off-by: James Morse <james.morse@....com>
> Reviewed-by: Fenghua Yu <fenghuay@...ia.com>
> Tested-by: Fenghua Yu <fenghuay@...dia.com>
> Cc: Peter Newman <peternewman@...gle.com>
> Signed-off-by: Ben Horgan <ben.horgan@....com>
> ---
> Changes since v3:
> Correct type checking, use mpam_feat_msmon_mbwu_<n>counter
> ---
>   drivers/resctrl/mpam_devices.c  | 48 ++++++++++++++++++++++++++++++++-
>   drivers/resctrl/mpam_internal.h |  2 ++
>   2 files changed, 49 insertions(+), 1 deletion(-)
> 
Reviewed-by: Gavin Shan <gshan@...hat.com>