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Date:   Thu, 16 Feb 2023 09:03:43 +0100
From:   Lukas Wunner <lukas@wunner.de>
To:     Ira Weiny <ira.weiny@intel.com>
Cc:     Bjorn Helgaas <helgaas@kernel.org>, linux-pci@vger.kernel.org,
        Gregory Price <gregory.price@memverge.com>,
        Jonathan Cameron <Jonathan.Cameron@huawei.com>,
        Dan Williams <dan.j.williams@intel.com>,
        Alison Schofield <alison.schofield@intel.com>,
        Vishal Verma <vishal.l.verma@intel.com>,
        Dave Jiang <dave.jiang@intel.com>,
        "Li, Ming" <ming4.li@intel.com>, Hillf Danton <hdanton@sina.com>,
        Ben Widawsky <bwidawsk@kernel.org>, linuxarm@huawei.com,
        linux-cxl@vger.kernel.org
Subject: Re: [PATCH v3 16/16] cxl/pci: Rightsize CDAT response allocation
Message-ID: <20230216080343.GA23125@wunner.de>
References: <cover.1676043318.git.lukas@wunner.de>
 <49c5299afc660ac33fee9a116ea37df0de938432.1676043318.git.lukas@wunner.de>
 <63ed7f50ed22b_19cbb72946d@iweiny-mobl.notmuch>
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On Wed, Feb 15, 2023 at 04:56:48PM -0800, Ira Weiny wrote:
> Lukas Wunner wrote:
> > Jonathan notes that cxl_cdat_get_length() and cxl_cdat_read_table()
> > allocate 32 dwords for the DOE response even though it may be smaller.
> > 
> > In the case of cxl_cdat_get_length(), only the second dword of the
> > response is of interest (it contains the length).  So reduce the
> > allocation to 2 dwords and let DOE discard the remainder.
> > 
> > In the case of cxl_cdat_read_table(), a correctly sized allocation for
> > the full CDAT already exists.  Let DOE write each table entry directly
> > into that allocation.  There's a snag in that the table entry is
> > preceded by a Table Access Response Header (1 dword).
> 
> Where is this 'Table Access Response Header' defined?

CXL r3.0 table 8-14 (sec 8.1.11.1, page 399).

I'll amend the commit message with a reference to the spec.

Thanks,

Lukas