PCI/P2PDMA: Gate the host bridge whitelist warning on verbose

calc_map_type_and_dist() prints every other diagnostic under its verbose
argument, but reaches the "Host bridge not in P2PDMA whitelist" warning
through host_bridge_whitelist(), which it hands acs_redirects instead.  A
caller that asked for a silent answer still gets the warning whenever any
port on the path has an ACS redirect bit set, the CPU is not whitelisted by
cpu_supports_p2pdma(), and the host bridge is not in
pci_p2pdma_whitelist[].

pci_p2pmem_find_many() is such a caller. It sweeps every device with
published p2pmem and asks for the distance to each client with
verbose=false, and pci_p2pdma_distance_many() recomputes rather than
consulting the map_types cache, so the warning repeats on every sweep.

The argument was never meant to say "ACS redirects were found". When commit
cf201bfe8cdc ("PCI/P2PDMA: Warn if host bridge not in whitelist") added it,
acs_redirects was a bool pointer that the quiet entry point passed as NULL:

  if (verbose)
	  map = calc_map_type_and_dist_warn(provider, pci_client,
					    &distance);
  else
	  map = calc_map_type_and_dist(provider, pci_client,
				       &distance, NULL, NULL);

so the argument was true on exactly the path that commit describes.
Folding the two entry points into one verbose flag turned the pointer into
a value and left the call site alone, silently narrowing the warning to
paths that carry an ACS redirect.

Pass verbose. This also restores the warning for a verbose caller that
takes the host bridge route with no ACS redirect on the path, which until
now was told it could not use peer-to-peer DMA without being told which
vendor and device would have to be added to the whitelist.

Fixes: d1b8dc09dd71 ("PCI/P2PDMA: Simplify distance calculation")
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Tested-by: Tushar Dave <tdave@nvidia.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
Link: https://patch.msgid.link/20260830-batch-p2p-fixes-v1-5-5044e8dfbe2e@nvidia.com

1 files changed, 1 insertions, 3 deletions

diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c
index bf5af4555f99..c8c414af7078 100644
--- a/drivers/pci/p2pdma.c
+++ b/drivers/pci/p2pdma.c
@@ -715,7 +715,6 @@ 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 acs_redirects = false;
 	struct pci_p2pdma *p2pdma;
 	struct seq_buf acs_list;
 	int acs_cnt = 0;
@@ -786,11 +785,10 @@ check_b_path_acs:
 		pci_warn(client, "to disable ACS redirect for this path, add the kernel parameter: pci=disable_acs_redir=%s\n",
 			 seq_buf_str(&acs_list));
 	}
-	acs_redirects = true;
 
 map_through_host_bridge:
 	if (!cpu_supports_p2pdma() &&
-	    !host_bridge_whitelist(provider, client, acs_redirects)) {
+	    !host_bridge_whitelist(provider, client, verbose)) {
 		if (verbose)
 			pci_warn(client, "cannot be used for peer-to-peer DMA as the client and provider (%s) do not share an upstream bridge or whitelisted host bridge\n",
 				 pci_name(provider));