Re: [RFC PATCH 0/1] cxl: Media Operations

[Jonathan Cameron <jonathan.cameron@huawei.com>]

On Mon, 23 Mar 2026 13:40:12 -0700
Davidlohr Bueso <dave@stgolabs.net> wrote:

> Hello,
> 
> This implements support for Media Operation cmd. It is marked RFC because of these
> noteworthy points:
> 
>  (i) Sysfs interfaces. These changes implement 'security/zero' and multiplex
>      'security/sanitize' to allow dpa, len pairs for the range (no impact for
>      current usage as whole-device). This breaks the 1 value per file "rule",
>      and would be a first for drivers/cxl/*, so am I open to suggestions.     

Value is a vague sort of term.  It's one thing (an range) so seems fine to me.

>   
>  (ii) Background cmd handling semantics. Media operations are synchronous,
>       which for raged zeroing operations makes sense and for range sanitize

ranged

>       differs from the current async handling for whole-device, so user response
>       differs significantly, something I am not crazy about. Another downside
>       of this is that it exposes lock hold times to be user-controllable, but is
>       no different than what we do for fw. Fundamentally, users have the
>       responsibility to break up the work into sane ranges.

We could apply a limit on this and make that discoverable via another sysfs attribute.
So let userspace request in say 1Gig chunks.  Would have to check that the device
supports that granularity though.
I don't think there is anything in the spec today to let us query how long
something takes (which would be a better way to bound this).


> Further, this is
>       without considering abortable bg cmds[0], which, per-spec, are unsupported
>       today for media operations.
> 
> Tested with qemu + fixlets (https://lore.kernel.org/all/20260319184256.3762391-1-dave@stgolabs.net/)

I think those all landed upstream today and are getting pulled into qemu stable as well.

> 
> Applies against latest 'next' from cxl.git.
> 
> [0] https://lore.kernel.org/all/20250617193611.564668-1-dave@stgolabs.net/
> 
> Thanks!
> 
> Davidlohr Bueso (1):
>   cxl/mbox: Support Media Operation
> 
>  Documentation/ABI/testing/sysfs-bus-cxl |  31 +++-
>  drivers/cxl/core/mbox.c                 | 235 ++++++++++++++++++++++++
>  drivers/cxl/core/memdev.c               |  45 ++++-
>  drivers/cxl/cxlmem.h                    |  59 ++++++
>  drivers/cxl/pci.c                       |   4 +
>  5 files changed, 369 insertions(+), 5 deletions(-)
> 
> --
> 2.39.5
> 
>