A lot of root complexes can still do P2P even when PCI devices
don't share a common upstream bridge.
Start adding a whitelist and allow P2P if both participants are
attached to known good root complex.
Signed-off-by: Christian König <christian.koenig@xxxxxxx>
---
drivers/pci/p2pdma.c | 38 +++++++++++++++++++++++++++++++++++---
1 file changed, 35 insertions(+), 3 deletions(-)
diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c
index c52298d76e64..212baaa7f93b 100644
--- a/drivers/pci/p2pdma.c
+++ b/drivers/pci/p2pdma.c
@@ -274,6 +274,31 @@ static void seq_buf_print_bus_devfn(struct seq_buf *buf, struct pci_dev *pdev)
seq_buf_printf(buf, "%s;", pci_name(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;
+
+ /* TODO: Extend that to a proper whitelist */
+ return false;
+}
+
/*
* Find the distance through the nearest common upstream bridge between
* two PCI devices.
@@ -317,13 +342,13 @@ 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 +379,13 @@ 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:
--
2.17.1
