Re: [PATCH v5 4/9] cxl/mem: Add basic IOCTL interface

[Jonathan Cameron]

On Tue, 16 Feb 2021 20:09:53 -0800
Ben Widawsky <ben.widawsky@xxxxxxxxx> wrote:

> Add a straightforward IOCTL that provides a mechanism for userspace to
> query the supported memory device commands. CXL commands as they appear
> to userspace are described as part of the UAPI kerneldoc. The command
> list returned via this IOCTL will contain the full set of commands that
> the driver supports, however, some of those commands may not be
> available for use by userspace.
> 
> Memory device commands first appear in the CXL 2.0 specification. They
> are submitted through a mailbox mechanism specified in the CXL 2.0
> specification.
> 
> The send command allows userspace to issue mailbox commands directly to
> the hardware. The list of available commands to send are the output of
> the query command. The driver verifies basic properties of the command
> and possibly inspect the input (or output) payload to determine whether
> or not the command is allowed (or might taint the kernel).
> 
> Reported-by: kernel test robot <lkp@xxxxxxxxx> # bug in earlier revision
> Reported-by: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>
> Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
> Signed-off-by: Ben Widawsky <ben.widawsky@xxxxxxxxx>
> Reviewed-by: Dan Williams <dan.j.williams@xxxxxxxxx> (v2)

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>