cxl: Fail AFU initialisation if an invalid configuration record is found

If an AFU claims to have a configuration record but doesn't actually
contain a vendor and device ID, fail the AFU initialisation. Right now
this is just a way of politely letting AFU developers know that they
need to fix their config space, but later on we may expose the AFUs as
actual PCI devices in their own right and don't want to inadvertendly
expose an AFU with a bad config space.
Signed-off-by: Ian Munsie <imunsie@au1.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

drivers/misc/cxl/pci.c

@@ -598,6 +598,8 @@ static int cxl_read_afu_descriptor(struct cxl_afu *afu)
 
 static int cxl_afu_descriptor_looks_ok(struct cxl_afu *afu)
 {
+	int i;
+
 	if (afu->psa && afu->adapter->ps_size <
 			(afu->pp_offset + afu->pp_size*afu->max_procs_virtualised)) {
 		dev_err(&afu->dev, "per-process PSA can't fit inside the PSA!\n");
@@ -607,6 +609,13 @@ static int cxl_afu_descriptor_looks_ok(struct cxl_afu *afu)
 	if (afu->pp_psa && (afu->pp_size < PAGE_SIZE))
 		dev_warn(&afu->dev, "AFU uses < PAGE_SIZE per-process PSA!");
 
+	for (i = 0; i < afu->crs_num; i++) {
+		if ((cxl_afu_cr_read32(afu, i, 0) == 0)) {
+			dev_err(&afu->dev, "ABORTING: AFU configuration record %i is invalid\n", i);
+			return -EINVAL;
+		}
+	}
+
 	return 0;
 }