Re: [PATCH v12 1/6] cxl/mbox: Add GET_POISON_LIST mailbox command

[Dan Williams <dan.j.williams@intel.com>]

Alison Schofield wrote:
> On Tue, Apr 11, 2023 at 06:47:56PM -0700, Dan Williams wrote:
> > alison.schofield@ wrote:
> > > From: Alison Schofield <alison.schofield@intel.com>
> > > 
> 
> follow up on the deprecate patch...
> 
> snip
> 
> > 
> > With this new interface I do not expect we want to support user tooling
> > that wants to retrieve the list via ioctl. So I think this wants a
> > lead-in patch that deprecates the poison command support so that the
> > linux-cxl community only has one mechanism to maintain going forward.
> > 
> > Something like the below as a lead-in, and then you would add code to
> > cxl_walk_cel() to set a flag for the "get poison" machinery.
> > 
> > -- >8 --
> > From f2cd1d1e09fe6f36255f3b8cd831b2b4903045d4 Mon Sep 17 00:00:00 2001
> > From: Dan Williams <dan.j.williams@intel.com>
> > Date: Tue, 11 Apr 2023 17:48:45 -0700
> > Subject: [PATCH] cxl/mbox: Deprecate poison commands
> > 
> > The CXL subsystem is adding a formal mechanism for retrieving the poison
> > list. Minimize the maintenance burden going forward, and maximize the
> > investment in common tooling by deprecating direct user access to issue
> > this command outside of CXL_MEM_RAW_COMMANDS debug scenarios.
> 
> I'm expanding the scope of this deprecate patch to include Scan
> commands, and want to make above statement correct, wrt what is
> allowed in raw mode.
> 
> Today, Scan Media (& Results) are not allowed in raw.
> It seems like in the spirit of raw, we should allow the scans. That
> would be same as the raw allowed commands Get Poison, Inject & Clear.
> 
> Thoughts?

The goal of blocking commands even for raw access is for the kernel to
say "hey, there's a formal interface for this, use that instead". At the
same time there is the "raw_allow_all" mechanism for those debug
scenarios to opt-in and say "I really know what I am doing". I think the
raw_allow_all hurdle is high enough to prevent splintering of user
tooling and encourage collaboration on the commons.

So I would say feel free to continue to list commands in
cxl_disabled_raw_commands as a way to document the commands that we,
linux-cxl@ community, believe need to be kernel managed. Rely on
raw_allow_all as the release valve for expert debugging.