[PATCH 02/13] PCI/P2PDMA: Report ACS ports when the paths share no upstream bridge

[Leon Romanovsky]

From: Leon Romanovsky <leonro@xxxxxxxxxx>

A provider and a client below different Root Ports share no upstream
bridge, so the search ends without a match and the walk takes the
host-bridge route directly. Neither path is examined for ACS, so no
redirect diagnostic is emitted and the host-bridge whitelist warning
stays suppressed.

Examine the paths before taking that route, so every redirecting port is
named in the pci=disable_acs_redir= hint. The mapping type is unchanged.

Signed-off-by: Leon Romanovsky <leonro@xxxxxxxxxx>
---
 drivers/pci/p2pdma.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c
index 2d3b380cc578..801c183ae6b7 100644
--- a/drivers/pci/p2pdma.c
+++ b/drivers/pci/p2pdma.c
@@ -703,6 +703,7 @@ calc_map_type_and_dist(struct pci_dev *provider, struct pci_dev *client,
 {
 	enum pci_p2pdma_map_type map_type = PCI_P2PDMA_MAP_THRU_HOST_BRIDGE;
 	struct pci_dev *a = provider, *b = client, *bb;
+	bool no_common_upstream = false;
 	bool acs_redirects = false;
 	struct pci_p2pdma *p2pdma;
 	struct seq_buf acs_list;
@@ -740,8 +741,12 @@ calc_map_type_and_dist(struct pci_dev *provider, struct pci_dev *client,
 		dist_a++;
 	}
 
-	*dist = dist_a + dist_b;
-	goto map_through_host_bridge;
+	/*
+	 * The paths share no upstream bridge, so the request can only reach
+	 * the peer through the host bridge. Examine the client path anyway,
+	 * so the diagnostics below name every ACS port on both paths.
+	 */
+	no_common_upstream = true;
 
 check_b_path_acs:
 	bb = b;
@@ -761,6 +766,9 @@ calc_map_type_and_dist(struct pci_dev *provider, struct pci_dev *client,
 	*dist = dist_a + dist_b;
 
 	if (!acs_cnt) {
+		if (no_common_upstream)
+			goto map_through_host_bridge;
+
 		map_type = PCI_P2PDMA_MAP_BUS_ADDR;
 		goto done;
 	}

-- 
2.55.0