linux-kernel - Re: [RFC PATCH v3 14/16] cxl/mem: Use CEL for enabling commands

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Date:   Thu, 14 Jan 2021 10:13:40 -0800
From:   Ben Widawsky <ben.widawsky@...el.com>
To:     Jonathan Cameron <Jonathan.Cameron@...wei.com>
Cc:     linux-cxl@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-pci@...r.kernel.org, linux-acpi@...r.kernel.org,
        Ira Weiny <ira.weiny@...el.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Vishal Verma <vishal.l.verma@...el.com>,
        "Kelley, Sean V" <sean.v.kelley@...el.com>,
        Rafael Wysocki <rafael.j.wysocki@...el.com>,
        Bjorn Helgaas <helgaas@...nel.org>,
        Jon Masters <jcm@...masters.org>,
        Chris Browy <cbrowy@...ry-design.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Christoph Hellwig <hch@...radead.org>,
        daniel.lll@...baba-inc.com
Subject: Re: [RFC PATCH v3 14/16] cxl/mem: Use CEL for enabling commands

On 21-01-14 18:02:11, Jonathan Cameron wrote:
> On Mon, 11 Jan 2021 14:51:19 -0800
> Ben Widawsky <ben.widawsky@...el.com> wrote:
> 
> > The Command Effects Log (CEL) is specified in the CXL 2.0 specification.
> > The CEL is one of two types of logs, the other being vendor specific.
> > They are distinguished in hardware/spec via UUID. The CEL is immediately
> > useful for 2 things:
> > 1. Determine which optional commands are supported by the CXL device.
> > 2. Enumerate any vendor specific commands
> > 
> > The CEL can be used by the driver to determine which commands are
> > available in the hardware (though it isn't, yet). That set of commands
> > might itself be a subset of commands which are available to be used via
> > CXL_MEM_SEND_COMMAND IOCTL.
> > 
> > Prior to this, all commands that the driver exposed were explicitly
> > enabled. After this, only those commands that are found in the CEL are
> > enabled.
> > 
> > Signed-off-by: Ben Widawsky <ben.widawsky@...el.com>
> 
> This patch made me wonder if the model for the command in quite right.
> I think it would end up simpler with a pair of payload pointers for send
> and receive (that can be equal when it makes sense).
> 
> A few other things inline.
> 
> Jonathan

I'll address the others separately, but could you elaborate on this? I'm not
sure I follow your meaning.

[snip]