linux-kernel - RE: [PATCH V13 8/9] cxl/port: Retry reading CDAT on failure

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Date:   Thu, 14 Jul 2022 09:27:04 -0700
From:   Dan Williams <dan.j.williams@...el.com>
To:     <ira.weiny@...el.com>, Dan Williams <dan.j.williams@...el.com>,
        "Bjorn Helgaas" <bhelgaas@...gle.com>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>
CC:     Ira Weiny <ira.weiny@...el.com>,
        Ben Widawsky <bwidawsk@...nel.org>,
        Alison Schofield <alison.schofield@...el.com>,
        Lukas Wunner <lukas@...ner.de>,
        Vishal Verma <vishal.l.verma@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        <linux-kernel@...r.kernel.org>, <linux-cxl@...r.kernel.org>,
        <linux-pci@...r.kernel.org>
Subject: RE: [PATCH V13 8/9] cxl/port: Retry reading CDAT on failure

ira.weiny@ wrote:
> From: Ira Weiny <ira.weiny@...el.com>
> 
> The CDAT read may fail for a number of reasons but mainly it is possible
> to get different parts of a valid state.  The checksum in the CDAT table
> protects against this.

I don't know what "different parts of a valid state" means. The CDAT
should not be changing as it is being read unless someone is issuing a
set-partition while the DOE operation is happening. Rather than
arbitrary retries, block out set-partition while CDAT is being read.

You can use {set,clear}_exclusive_cxl_commands() to temporarily lock out
set-partition while the CDAT read is happening.

...and since this series is only for enabling