PCI/P2PDMA: Simplify distance calculation
authorChristoph Hellwig <hch@lst.de>
Mon, 14 Jun 2021 05:53:10 +0000 (07:53 +0200)
committerBjorn Helgaas <bhelgaas@google.com>
Wed, 16 Jun 2021 21:09:41 +0000 (16:09 -0500)
Merge __calc_map_type_and_dist() and calc_map_type_and_dist_warn() into
calc_map_type_and_dist() to simplify the code a bit.  This now means we add
the devfn strings to the acs_buf unconditionally even if the buffer is not
printed, but that is not a lot of overhead and keeps the code much simpler.

Link: https://lore.kernel.org/r/20210614055310.3960791-1-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
drivers/pci/p2pdma.c

index deb097c..ca2574d 100644 (file)
@@ -388,79 +388,6 @@ static bool host_bridge_whitelist(struct pci_dev *a, struct pci_dev *b,
        return false;
 }
 
-static enum pci_p2pdma_map_type
-__calc_map_type_and_dist(struct pci_dev *provider, struct pci_dev *client,
-               int *dist, bool *acs_redirects, struct seq_buf *acs_list)
-{
-       struct pci_dev *a = provider, *b = client, *bb;
-       int dist_a = 0;
-       int dist_b = 0;
-       int acs_cnt = 0;
-
-       if (acs_redirects)
-               *acs_redirects = false;
-
-       /*
-        * Note, we don't need to take references to devices returned by
-        * pci_upstream_bridge() seeing we hold a reference to a child
-        * device which will already hold a reference to the upstream bridge.
-        */
-
-       while (a) {
-               dist_b = 0;
-
-               if (pci_bridge_has_acs_redir(a)) {
-                       seq_buf_print_bus_devfn(acs_list, a);
-                       acs_cnt++;
-               }
-
-               bb = b;
-
-               while (bb) {
-                       if (a == bb)
-                               goto check_b_path_acs;
-
-                       bb = pci_upstream_bridge(bb);
-                       dist_b++;
-               }
-
-               a = pci_upstream_bridge(a);
-               dist_a++;
-       }
-
-       if (dist)
-               *dist = dist_a + dist_b;
-
-       return PCI_P2PDMA_MAP_THRU_HOST_BRIDGE;
-
-check_b_path_acs:
-       bb = b;
-
-       while (bb) {
-               if (a == bb)
-                       break;
-
-               if (pci_bridge_has_acs_redir(bb)) {
-                       seq_buf_print_bus_devfn(acs_list, bb);
-                       acs_cnt++;
-               }
-
-               bb = pci_upstream_bridge(bb);
-       }
-
-       if (dist)
-               *dist = dist_a + dist_b;
-
-       if (acs_cnt) {
-               if (acs_redirects)
-                       *acs_redirects = true;
-
-               return PCI_P2PDMA_MAP_THRU_HOST_BRIDGE;
-       }
-
-       return PCI_P2PDMA_MAP_BUS_ADDR;
-}
-
 static unsigned long map_types_idx(struct pci_dev *client)
 {
        return (pci_domain_nr(client->bus) << 16) |
@@ -502,63 +429,96 @@ static unsigned long map_types_idx(struct pci_dev *client)
  * PCI_P2PDMA_MAP_THRU_HOST_BRIDGE with the distance set to the number of
  * ports per above. If the device is not in the whitelist, return
  * PCI_P2PDMA_MAP_NOT_SUPPORTED.
- *
- * If any ACS redirect bits are set, then acs_redirects boolean will be set
- * to true and their PCI device names will be appended to the acs_list
- * seq_buf. This seq_buf is used to print a warning informing the user how
- * to disable ACS using a command line parameter.  (See
- * calc_map_type_and_dist_warn() below)
  */
 static enum pci_p2pdma_map_type
 calc_map_type_and_dist(struct pci_dev *provider, struct pci_dev *client,
-               int *dist, bool *acs_redirects, struct seq_buf *acs_list)
+               int *dist, bool verbose)
 {
-       enum pci_p2pdma_map_type map_type;
+       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 seq_buf acs_list;
+       int acs_cnt = 0;
+       int dist_a = 0;
+       int dist_b = 0;
+       char buf[128];
+
+       seq_buf_init(&acs_list, buf, sizeof(buf));
+
+       /*
+        * Note, we don't need to take references to devices returned by
+        * pci_upstream_bridge() seeing we hold a reference to a child
+        * device which will already hold a reference to the upstream bridge.
+        */
+       while (a) {
+               dist_b = 0;
 
-       map_type = __calc_map_type_and_dist(provider, client, dist,
-                                           acs_redirects, acs_list);
+               if (pci_bridge_has_acs_redir(a)) {
+                       seq_buf_print_bus_devfn(&acs_list, a);
+                       acs_cnt++;
+               }
 
-       if (map_type == PCI_P2PDMA_MAP_THRU_HOST_BRIDGE) {
-               if (!cpu_supports_p2pdma() &&
-                   !host_bridge_whitelist(provider, client, acs_redirects))
-                       map_type = PCI_P2PDMA_MAP_NOT_SUPPORTED;
+               bb = b;
+
+               while (bb) {
+                       if (a == bb)
+                               goto check_b_path_acs;
+
+                       bb = pci_upstream_bridge(bb);
+                       dist_b++;
+               }
+
+               a = pci_upstream_bridge(a);
+               dist_a++;
        }
 
-       if (provider->p2pdma)
-               xa_store(&provider->p2pdma->map_types, map_types_idx(client),
-                        xa_mk_value(map_type), GFP_KERNEL);
+       *dist = dist_a + dist_b;
+       goto map_through_host_bridge;
 
-       return map_type;
-}
+check_b_path_acs:
+       bb = b;
 
-static enum pci_p2pdma_map_type
-calc_map_type_and_dist_warn(struct pci_dev *provider, struct pci_dev *client,
-                           int *dist)
-{
-       struct seq_buf acs_list;
-       bool acs_redirects;
-       char buf[128];
-       int ret;
+       while (bb) {
+               if (a == bb)
+                       break;
 
-       seq_buf_init(&acs_list, buf, sizeof(buf));
+               if (pci_bridge_has_acs_redir(bb)) {
+                       seq_buf_print_bus_devfn(&acs_list, bb);
+                       acs_cnt++;
+               }
 
-       ret = calc_map_type_and_dist(provider, client, dist, &acs_redirects,
-                                    &acs_list);
-       if (acs_redirects) {
+               bb = pci_upstream_bridge(bb);
+       }
+
+       *dist = dist_a + dist_b;
+
+       if (!acs_cnt) {
+               map_type = PCI_P2PDMA_MAP_BUS_ADDR;
+               goto done;
+       }
+
+       if (verbose) {
+               acs_list.buffer[acs_list.len-1] = 0; /* drop final semicolon */
                pci_warn(client, "ACS redirect is set between the client and provider (%s)\n",
                         pci_name(provider));
-               /* Drop final semicolon */
-               acs_list.buffer[acs_list.len-1] = 0;
                pci_warn(client, "to disable ACS redirect for this path, add the kernel parameter: pci=disable_acs_redir=%s\n",
                         acs_list.buffer);
        }
+       acs_redirects = true;
 
-       if (ret == PCI_P2PDMA_MAP_NOT_SUPPORTED) {
-               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));
+map_through_host_bridge:
+       if (!cpu_supports_p2pdma() &&
+           !host_bridge_whitelist(provider, client, acs_redirects)) {
+               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));
+               map_type = PCI_P2PDMA_MAP_NOT_SUPPORTED;
        }
-
-       return ret;
+done:
+       if (provider->p2pdma)
+               xa_store(&provider->p2pdma->map_types, map_types_idx(client),
+                        xa_mk_value(map_type), GFP_KERNEL);
+       return map_type;
 }
 
 /**
@@ -599,12 +559,8 @@ int pci_p2pdma_distance_many(struct pci_dev *provider, struct device **clients,
                        return -1;
                }
 
-               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);
+               map = calc_map_type_and_dist(provider, pci_client, &distance,
+                                            verbose);
 
                pci_dev_put(pci_client);