Merge tag 'cxl-fixes-6.9-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/cxl/cxl

Pull cxl fix from Dave Jiang:
 "Add missing RCH support for endpoint access_coordinate calculation.

  A late bug was reported by Robert Richter that the Restricted CXL Host
  (RCH) support was missing in the CXL endpoint access_coordinate
  calculation.

  The missing support causes the topology iterator to stumble over a
  NULL pointer and triggers a kernel OOPS on a platform with CXL 1.1
  support.

  The fix bypasses RCH topology as the access_coordinate calculation is
  not necessary since RCH does not support hotplug and the memory region
  exported should be covered by the HMAT table already.

  A unit test is also added to cxl_test to check against future
  regressions on the topology iterator"

* tag 'cxl-fixes-6.9-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/cxl/cxl:
  cxl: Fix cxl_endpoint_get_perf_coordinate() support for RCH

Author: torvalds

drivers/cxl/core/port.c

@@ -2184,6 +2184,7 @@ static bool parent_port_is_cxl_root(struct cxl_port *port)
 int cxl_endpoint_get_perf_coordinates(struct cxl_port *port,
 				      struct access_coordinate *coord)
 {
+	struct cxl_memdev *cxlmd = to_cxl_memdev(port->uport_dev);
 	struct access_coordinate c[] = {
 		{
 			.read_bandwidth = UINT_MAX,
@@ -2197,12 +2198,20 @@ int cxl_endpoint_get_perf_coordinates(struct cxl_port *port,
 	struct cxl_port *iter = port;
 	struct cxl_dport *dport;
 	struct pci_dev *pdev;
+	struct device *dev;
 	unsigned int bw;
 	bool is_cxl_root;
 
 	if (!is_cxl_endpoint(port))
 		return -EINVAL;
 
+	/*
+	 * Skip calculation for RCD. Expectation is HMAT already covers RCD case
+	 * since RCH does not support hotplug.
+	 */
+	if (cxlmd->cxlds->rcd)
+		return 0;
+
 	/*
 	 * Exit the loop when the parent port of the current iter port is cxl
 	 * root. The iterative loop starts at the endpoint and gathers the
@@ -2232,8 +2241,12 @@ int cxl_endpoint_get_perf_coordinates(struct cxl_port *port,
 		return -EINVAL;
 	cxl_coordinates_combine(c, c, dport->coord);
 
+	dev = port->uport_dev->parent;
+	if (!dev_is_pci(dev))
+		return -ENODEV;
+
 	/* Get the calculated PCI paths bandwidth */
-	pdev = to_pci_dev(port->uport_dev->parent);
+	pdev = to_pci_dev(dev);
 	bw = pcie_bandwidth_available(pdev, NULL, NULL, NULL);
 	if (bw == 0)
 		return -ENXIO;

tools/testing/cxl/test/cxl.c

@@ -1001,6 +1001,7 @@ static void mock_cxl_endpoint_parse_cdat(struct cxl_port *port)
 	struct cxl_memdev *cxlmd = to_cxl_memdev(port->uport_dev);
 	struct cxl_dev_state *cxlds = cxlmd->cxlds;
 	struct cxl_memdev_state *mds = to_cxl_memdev_state(cxlds);
+	struct access_coordinate ep_c[ACCESS_COORDINATE_MAX];
 	struct range pmem_range = {
 		.start = cxlds->pmem_res.start,
 		.end = cxlds->pmem_res.end,
@@ -1020,6 +1021,12 @@ static void mock_cxl_endpoint_parse_cdat(struct cxl_port *port)
 		dpa_perf_setup(port, &pmem_range, &mds->pmem_perf);
 
 	cxl_memdev_update_perf(cxlmd);
+
+	/*
+	 * This function is here to only test the topology iterator. It serves
+	 * no other purpose.
+	 */
+	cxl_endpoint_get_perf_coordinates(port, ep_c);
 }
 
 static struct cxl_mock_ops cxl_mock_ops = {