cxl, acpi/hmat: Update CXL access coordinates directly instead of through HMAT

The current implementation of CXL memory hotplug notifier gets called
before the HMAT memory hotplug notifier. The CXL driver calculates the
access coordinates (bandwidth and latency values) for the CXL end to
end path (i.e. CPU to endpoint). When the CXL region is onlined, the CXL
memory hotplug notifier writes the access coordinates to the HMAT target
structs. Then the HMAT memory hotplug notifier is called and it creates
the access coordinates for the node sysfs attributes.

During testing on an Intel platform, it was found that although the
newly calculated coordinates were pushed to sysfs, the sysfs attributes for
the access coordinates showed up with the wrong initiator. The system has
4 nodes (0, 1, 2, 3) where node 0 and 1 are CPU nodes and node 2 and 3 are
CXL nodes. The expectation is that node 2 would show up as a target to node
0:
/sys/devices/system/node/node2/access0/initiators/node0

However it was observed that node 2 showed up as a target under node 1:
/sys/devices/system/node/node2/access0/initiators/node1

The original intent of the 'ext_updated' flag in HMAT handling code was to
stop HMAT memory hotplug callback from clobbering the access coordinates
after CXL has injected its calculated coordinates and replaced the generic
target access coordinates provided by the HMAT table in the HMAT target
structs. However the flag is hacky at best and blocks the updates from
other CXL regions that are onlined in the same node later on. Remove the
'ext_updated' flag usage and just update the access coordinates for the
nodes directly without touching HMAT target data.

The hotplug memory callback ordering is changed. Instead of changing CXL,
move HMAT back so there's room for the levels rather than have CXL share
the same level as SLAB_CALLBACK_PRI. The change will resulting in the CXL
callback to be executed after the HMAT callback.

With the change, the CXL hotplug memory notifier runs after the HMAT
callback. The HMAT callback will create the node sysfs attributes for
access coordinates. The CXL callback will write the access coordinates to
the now created node sysfs attributes directly and will not pollute the
HMAT target values.

A nodemask is introduced to keep track if a node has been updated and
prevents further updates.

Fixes: 067353a46d8c ("cxl/region: Add memory hotplug notifier for cxl region")
Cc: stable@vger.kernel.org
Tested-by: Marc Herbert <marc.herbert@linux.intel.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Link: https://patch.msgid.link/20250829222907.1290912-4-dave.jiang@intel.com
Signed-off-by: Dave Jiang <dave.jiang@intel.com>

0 files changed, 0 insertions, 0 deletions