1 files changed, 38 insertions, 6 deletions

diff --git a/arch/x86/kernel/amd_nb.c b/arch/x86/kernel/amd_nb.c
index 19d489ee2b1e..cc34266e3c62 100644
--- a/arch/x86/kernel/amd_nb.c
+++ b/arch/x86/kernel/amd_nb.c
@@ -213,7 +213,10 @@ int amd_cache_northbridges(void)
         const struct pci_device_id *root_ids = amd_root_ids;
         struct pci_dev *root, *misc, *link;
         struct amd_northbridge *nb;
-        u16 i = 0;
+        u16 roots_per_misc = 0;
+        u16 misc_count = 0;
+        u16 root_count = 0;
+        u16 i, j;
 
         if (amd_northbridges.num)
                 return 0;
@@ -226,26 +229,55 @@ int amd_cache_northbridges(void)
 
         misc = NULL;
         while ((misc = next_northbridge(misc, misc_ids)) != NULL)
-                i++;
+                misc_count++;
 
-        if (!i)
+        if (!misc_count)
                 return -ENODEV;
 
-        nb = kcalloc(i, sizeof(struct amd_northbridge), GFP_KERNEL);
+        root = NULL;
+        while ((root = next_northbridge(root, root_ids)) != NULL)
+                root_count++;
+
+        if (root_count) {
+                roots_per_misc = root_count / misc_count;
+
+                /*
+                 * There should be _exactly_ N roots for each DF/SMN
+                 * interface.
+                 */
+                if (!roots_per_misc || (root_count % roots_per_misc)) {
+                        pr_info("Unsupported AMD DF/PCI configuration found\n");
+                        return -ENODEV;
+                }
+        }
+
+        nb = kcalloc(misc_count, sizeof(struct amd_northbridge), GFP_KERNEL);
         if (!nb)
                 return -ENOMEM;
 
         amd_northbridges.nb = nb;
-        amd_northbridges.num = i;
+        amd_northbridges.num = misc_count;
 
         link = misc = root = NULL;
-        for (i = 0; i != amd_northbridges.num; i++) {
+        for (i = 0; i < amd_northbridges.num; i++) {
                 node_to_amd_nb(i)->root = root =
                         next_northbridge(root, root_ids);
                 node_to_amd_nb(i)->misc = misc =
                         next_northbridge(misc, misc_ids);
                 node_to_amd_nb(i)->link = link =
                         next_northbridge(link, link_ids);
+
+                /*
+                 * If there are more PCI root devices than data fabric/
+                 * system management network interfaces, then the (N)
+                 * PCI roots per DF/SMN interface are functionally the
+                 * same (for DF/SMN access) and N-1 are redundant.  N-1
+                 * PCI roots should be skipped per DF/SMN interface so
+                 * the following DF/SMN interfaces get mapped to
+                 * correct PCI roots.
+                 */
+                for (j = 1; j < roots_per_misc; j++)
+                        root = next_northbridge(root, root_ids);
         }
 
         if (amd_gart_present())