Merge branch 'pci/peer-to-peer'

  - Add a whitelist of Root Complexes known to support peer-to-peer DMA
    between Root Ports (Christian König)

* pci/peer-to-peer:
  PCI/P2PDMA: Allow P2P DMA between any devices under AMD ZEN Root Complex

1 files changed, 35 insertions, 3 deletions

diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c
index c52298d76e64..742928d0053e 100644
--- a/drivers/pci/p2pdma.c
+++ b/drivers/pci/p2pdma.c
@@ -275,6 +275,30 @@ static void seq_buf_print_bus_devfn(struct seq_buf *buf, struct pci_dev *pdev)
 }
 
 /*
+ * If we can't find a common upstream bridge take a look at the root
+ * complex and compare it to a whitelist of known good hardware.
+ */
+static bool root_complex_whitelist(struct pci_dev *dev)
+{
+        struct pci_host_bridge *host = pci_find_host_bridge(dev->bus);
+        struct pci_dev *root = pci_get_slot(host->bus, PCI_DEVFN(0, 0));
+        unsigned short vendor, device;
+
+        if (!root)
+                return false;
+
+        vendor = root->vendor;
+        device = root->device;
+        pci_dev_put(root);
+
+        /* AMD ZEN host bridges can do peer to peer */
+        if (vendor == PCI_VENDOR_ID_AMD && device == 0x1450)
+                return true;
+
+        return false;
+}
+
+/*
  * Find the distance through the nearest common upstream bridge between
  * two PCI devices.
  *
@@ -317,13 +341,13 @@ static void seq_buf_print_bus_devfn(struct seq_buf *buf, struct pci_dev *pdev)
  * In this case, a list of all infringing bridge addresses will be
  * populated in acs_list (assuming it's non-null) for printk purposes.
  */
-static int upstream_bridge_distance(struct pci_dev *a,
-                                    struct pci_dev *b,
+static int upstream_bridge_distance(struct pci_dev *provider,
+                                    struct pci_dev *client,
                                     struct seq_buf *acs_list)
 {
+        struct pci_dev *a = provider, *b = client, *bb;
         int dist_a = 0;
         int dist_b = 0;
-        struct pci_dev *bb = NULL;
         int acs_cnt = 0;
 
         /*
@@ -354,6 +378,14 @@ static int upstream_bridge_distance(struct pci_dev *a,
                 dist_a++;
         }
 
+        /*
+         * Allow the connection if both devices are on a whitelisted root
+         * complex, but add an arbitary large value to the distance.
+         */
+        if (root_complex_whitelist(provider) &&
+            root_complex_whitelist(client))
+                return 0x1000 + dist_a + dist_b;
+
         return -1;
 
 check_b_path_acs: