cxl/region: Add memory hotplug notifier for cxl region

When the CXL region is formed, the driver computes the performance data
for the region. However this data is not available at the node data
collection that has been populated by the HMAT during kernel
initialization. Add a memory hotplug notifier to update the access
coordinates to the 'struct memory_target' context kept by the
HMAT_REPORTING code.

Add CXL_CALLBACK_PRI for a memory hotplug callback priority. Set the
priority number to be called before HMAT_CALLBACK_PRI. The CXL update must
happen before hmat_callback().

A new HMAT_REPORTING helper hmat_update_target_coordinates() is added in
order to allow CXL to update the memory_target access coordinates.

A new ext_updated member is added to the memory_target to indicate that
the access coordinates within the memory_target has been updated by an
external agent such as CXL. This prevents data being overwritten by the
hmat_update_target_attrs() triggered by hmat_callback().

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Rafael J. Wysocki <rafael@kernel.org>
Reviewed-by: Huang, Ying <ying.huang@intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Tested-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/20240308220055.2172956-12-dave.jiang@intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

1 files changed, 34 insertions, 0 deletions

diff --git a/drivers/acpi/numa/hmat.c b/drivers/acpi/numa/hmat.c
index 75e9aac43228..2c8ccc91ebe6 100644
--- a/drivers/acpi/numa/hmat.c
+++ b/drivers/acpi/numa/hmat.c
@@ -74,6 +74,7 @@ struct memory_target {
 	struct node_cache_attrs cache_attrs;
 	u8 gen_port_device_handle[ACPI_SRAT_DEVICE_HANDLE_SIZE];
 	bool registered;
+	bool ext_updated;	/* externally updated */
 };
 
 struct memory_initiator {
@@ -328,6 +329,35 @@ static void hmat_update_target_access(struct memory_target *target,
 	}
 }
 
+int hmat_update_target_coordinates(int nid, struct access_coordinate *coord,
+				   enum access_coordinate_class access)
+{
+	struct memory_target *target;
+	int pxm;
+
+	if (nid == NUMA_NO_NODE)
+		return -EINVAL;
+
+	pxm = node_to_pxm(nid);
+	guard(mutex)(&target_lock);
+	target = find_mem_target(pxm);
+	if (!target)
+		return -ENODEV;
+
+	hmat_update_target_access(target, ACPI_HMAT_READ_LATENCY,
+				  coord->read_latency, access);
+	hmat_update_target_access(target, ACPI_HMAT_WRITE_LATENCY,
+				  coord->write_latency, access);
+	hmat_update_target_access(target, ACPI_HMAT_READ_BANDWIDTH,
+				  coord->read_bandwidth, access);
+	hmat_update_target_access(target, ACPI_HMAT_WRITE_BANDWIDTH,
+				  coord->write_bandwidth, access);
+	target->ext_updated = true;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(hmat_update_target_coordinates);
+
 static __init void hmat_add_locality(struct acpi_hmat_locality *hmat_loc)
 {
 	struct memory_locality *loc;
@@ -699,6 +729,10 @@ static void hmat_update_target_attrs(struct memory_target *target,
 	u32 best = 0;
 	int i;
 
+	/* Don't update if an external agent has changed the data.  */
+	if (target->ext_updated)
+		return;
+
 	/* Don't update for generic port if there's no device handle */
 	if ((access == NODE_ACCESS_CLASS_GENPORT_SINK_LOCAL ||
 	     access == NODE_ACCESS_CLASS_GENPORT_SINK_CPU) &&