cxl/test: Skip cxl_setup_parent_dport() for emulated dports

The cxl_test unit test environment on qemu always hits below call trace
with KASAN enabled:

 BUG: KASAN: slab-out-of-bounds in cxl_setup_parent_dport+0x480/0x530 [cxl_core]
 Read of size 1 at addr ff110000676014f8 by task (udev-worker)/676[   24.424403] CPU: 2 PID: 676 Comm: (udev-worker) Tainted: G           O     N 6.10.0-qemucxl #1
 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS edk2-20240214-2.el9 02/14/2024
 Call Trace:
  <TASK>
  dump_stack_lvl+0xea/0x150
  print_report+0xce/0x610
  ? kasan_complete_mode_report_info+0x40/0x200
  kasan_report+0xcc/0x110
  __asan_report_load1_noabort+0x18/0x20
  cxl_setup_parent_dport+0x480/0x530 [cxl_core]
  cxl_mem_probe+0x49b/0xaa0 [cxl_mem]

cxl_test module models a CXL topology for testing, it creates some
emulated dports with platform devices in the CXL topology, so the
dport_dev of an emulated dport points to a platform device rather than a
pci device or a pci host bridge in the case. Currently,
cxl_setup_parent_dport() is used to set up RAS and AER capability on the
dport connected to the CXL memory device, but cxl_test does not support
RAS or AER functionality yet, so the fix is implementing a
__wrap_cxl_setup_parent_dport() to filter out all emulated dports,
guarantees only real dports can be handled by cxl_setup_parent_dport().

Fixes: f05fd10 ("cxl/pci: Add RCH downstream port AER register discovery")
Reported-by: Pengfei Xu <[email protected]>
Closes: https://lore.kernel.org/linux-cxl/[email protected]/T/#t
Signed-off-by: Li Ming <[email protected]>
Reviewed-by: Dan Williams <[email protected]>
Reviewed-by: Ira Weiny <[email protected]>
Reviewed-by: Alison Schofield <[email protected]>
Tested-by: Ira Weiny <[email protected]>
Tested-by: Alison Schofield <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Dave Jiang <[email protected]>

Author: ming4li

tools/testing/cxl/Kbuild

@@ -14,6 +14,7 @@ ldflags-y += --wrap=cxl_dvsec_rr_decode
 ldflags-y += --wrap=devm_cxl_add_rch_dport
 ldflags-y += --wrap=cxl_rcd_component_reg_phys
 ldflags-y += --wrap=cxl_endpoint_parse_cdat
+ldflags-y += --wrap=cxl_setup_parent_dport
 
 DRIVERS := ../../../drivers
 CXL_SRC := $(DRIVERS)/cxl

tools/testing/cxl/test/mock.c

@@ -299,6 +299,18 @@ void __wrap_cxl_endpoint_parse_cdat(struct cxl_port *port)
 }
 EXPORT_SYMBOL_NS_GPL(__wrap_cxl_endpoint_parse_cdat, CXL);
 
+void __wrap_cxl_setup_parent_dport(struct device *host, struct cxl_dport *dport)
+{
+	int index;
+	struct cxl_mock_ops *ops = get_cxl_mock_ops(&index);
+
+	if (!ops || !ops->is_mock_port(dport->dport_dev))
+		cxl_setup_parent_dport(host, dport);
+
+	put_cxl_mock_ops(index);
+}
+EXPORT_SYMBOL_NS_GPL(__wrap_cxl_setup_parent_dport, CXL);
+
 MODULE_LICENSE("GPL v2");
 MODULE_IMPORT_NS(ACPI);
 MODULE_IMPORT_NS(CXL);