On Tue, Feb 16, 2021 at 08:09:50PM -0800, Ben Widawsky wrote:

From: Dan Williams <redacted>

The CXL.mem protocol allows a device to act as a provider of "System
RAM" and/or "Persistent Memory" that is fully coherent as if the memory
was attached to the typical CPU memory controller.

With the CXL-2.0 specification a PCI endpoint can implement a "Type-3"
device interface and give the operating system control over "Host
Managed Device Memory". See section 2.3 Type 3 CXL Device.

The memory range exported by the device may optionally be described by
the platform firmware memory map, or by infrastructure like LIBNVDIMM to
provision persistent memory capacity from one, or more, CXL.mem devices.

A pre-requisite for Linux-managed memory-capacity provisioning is this
cxl_mem driver that can speak the mailbox protocol defined in section
8.2.8.4 Mailbox Registers.

For now just land the initial driver boiler-plate and Documentation/
infrastructure.

Link: https://www.computeexpresslink.org/download-the-specification
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Dan Williams <redacted>
Signed-off-by: Ben Widawsky <redacted>
Acked-by: David Rientjes <rientjes@google.com> (v1)

Reviewed-by: Konrad Rzeszutek Wilk <redacted>

Albeit you may want to modify 2020 to 2021 in the Copyright sections.