ndctl: Add support of qos_class for CXL CLI

From: Dave Jiang <dave.jiang@intel.com>
To: linux-cxl@vger.kernel.org, nvdimm@lists.linux.dev
Cc: vishal.l.verma@intel.com
Subject: ndctl: Add support of qos_class for CXL CLI
Date: Thu,  1 Feb 2024 16:05:03 -0700	[thread overview]
Message-ID: <20240201230646.1328211-1-dave.jiang@intel.com> (raw)

v5:
- split out test to its own bash script. (Vishal)
v4:
- Update against changes in kernel from multi to single qos_class entry
- Add test in cxl-topology.sh (Dan)
- See individual patch log for details
v3:
- Rebase against latest ndctl/pending branch.

The series adds support for the kernel enabling of QoS class in the v6.8
kernel. The kernel exports a qos_class token for the root decoders (CFMWS) and as
well as for the CXL memory devices. The qos_class exported for a device is
calculated by the driver during device probe. Currently a qos_class is exported
for the volatile partition (ram) and another for the persistent partition (pmem).
In the future qos_class will be exported for DCD regions. Display of qos_class is
through the CXL CLI list command.

A qos_class check as also been added for region creation. A warning is emitted
when the qos_class of a memory range of a CXL memory device being included in
the CXL region assembly does not match the qos_class of the root decoder. Options
are available to suppress the warning or to fail the region creation. This
enabling provides a guidance on flagging memory ranges being used is not
optimal for performance for the CXL region to be formed.