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References: <20230113175459.14825-1-james.morse@arm.com> <20230113175459.14825-10-james.morse@arm.com>
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From:   Peter Newman <peternewman@google.com>
Date:   Mon, 23 Jan 2023 16:33:45 +0100
Message-ID: <CALPaoCg4T52ju5XJC-BVX-EuZUtc67LruWbgyH5s8CoiEwOUPw@mail.gmail.com>
Subject: Re: [PATCH v2 09/18] x86/resctrl: Allow resctrl_arch_rmid_read() to sleep
To:     James Morse <james.morse@arm.com>
Cc:     x86@kernel.org, linux-kernel@vger.kernel.org,
        Fenghua Yu <fenghua.yu@intel.com>,
        Reinette Chatre <reinette.chatre@intel.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        H Peter Anvin <hpa@zytor.com>,
        Babu Moger <Babu.Moger@amd.com>,
        shameerali.kolothum.thodi@huawei.com,
        D Scott Phillips OS <scott@os.amperecomputing.com>,
        carl@os.amperecomputing.com, lcherian@marvell.com,
        bobo.shaobowang@huawei.com, tan.shaopeng@fujitsu.com,
        xingxin.hx@openanolis.org, baolin.wang@linux.alibaba.com,
        Jamie Iles <quic_jiles@quicinc.com>,
        Xin Hao <xhao@linux.alibaba.com>
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On Fri, Jan 13, 2023 at 6:56 PM James Morse <james.morse@arm.com> wrote:
> MPAM's cache occupancy counters can take a little while to settle once
> the monitor has been configured. The maximum settling time is described
> to the driver via a firmware table. The value could be large enough
> that it makes sense to sleep.

Would it be easier to return an error when reading the occupancy count
too soon after configuration? On Intel it is already normal for counter
reads to fail on newly-allocated RMIDs.

-Peter