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

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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
cf201bfe8c ("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: d1b8dc09dd ("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
This commit is contained in:
Leon Romanovsky 2026-08-30 14:16:23 +03:00 committed by Bjorn Helgaas
parent fa291d6429
commit 36038f0e83
1 changed files with 1 additions and 3 deletions
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4
drivers/pci/p2pdma.c
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@ -721,7 +721,6 @@ 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;
@ -792,11 +791,10 @@ calc_map_type_and_dist(struct pci_dev *provider, struct pci_dev *client,
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));