Add constant flags to indicate how two devices will be mapped or if they are unsupported. upstream_bridge_distance() will now return the mapping type and the distance in a passed-by-reference argument. This helps annotate the code better, but the main reason is so we can use the information to store the required mapping method in an xarray. Link: https://lore.kernel.org/r/20190730163545.4915-4-logang@xxxxxxxxxxxx Signed-off-by: Logan Gunthorpe <logang@xxxxxxxxxxxx> Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx> Reviewed-by: Christian König <christian.koenig@xxxxxxx> --- drivers/pci/p2pdma.c | 95 +++++++++++++++++++++++++++----------------- 1 file changed, 58 insertions(+), 37 deletions(-) diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c index 93fbda14f4a9..8f0688201aec 100644 --- a/drivers/pci/p2pdma.c +++ b/drivers/pci/p2pdma.c @@ -20,6 +20,13 @@ #include <linux/seq_buf.h> #include <linux/iommu.h> +enum pci_p2pdma_map_type { + PCI_P2PDMA_MAP_UNKNOWN = 0, + PCI_P2PDMA_MAP_NOT_SUPPORTED, + PCI_P2PDMA_MAP_BUS_ADDR, + PCI_P2PDMA_MAP_THRU_HOST_BRIDGE, +}; + struct pci_p2pdma { struct gen_pool *pool; bool p2pmem_published; @@ -313,34 +320,33 @@ static bool root_complex_whitelist(struct pci_dev *dev) * port of the switch, to the common upstream port, back up to the second * downstream port and then to Device B. * - * Any two devices that don't have a common upstream bridge will return -1. - * In this way devices on separate PCIe root ports will be rejected, which - * is what we want for peer-to-peer seeing each PCIe root port defines a - * separate hierarchy domain and there's no way to determine whether the root - * complex supports forwarding between them. + * Any two devices that cannot communicate using p2pdma will return + * PCI_P2PDMA_MAP_NOT_SUPPORTED. + * + * Any two devices that have a data path that goes through the host bridge + * will consult a whitelist. If the host bridges are on the whitelist, + * this function will return PCI_P2PDMA_MAP_THRU_HOST_BRIDGE. * - * In the case where two devices are connected to different PCIe switches, - * this function will still return a positive distance as long as both - * switches eventually have a common upstream bridge. Note this covers - * the case of using multiple PCIe switches to achieve a desired level of - * fan-out from a root port. The exact distance will be a function of the - * number of switches between Device A and Device B. + * If either bridge is not on the whitelist this function returns + * PCI_P2PDMA_MAP_NOT_SUPPORTED. * - * If a bridge which has any ACS redirection bits set is in the path - * then this functions will return -2. This is so we reject any - * cases where the TLPs are forwarded up into the root complex. - * In this case, a list of all infringing bridge addresses will be - * populated in acs_list (assuming it's non-null) for printk purposes. + * If a bridge which has any ACS redirection bits set is in the path, + * acs_redirects will be set to true. 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 *provider, - struct pci_dev *client, - struct seq_buf *acs_list) +static enum pci_p2pdma_map_type +upstream_bridge_distance(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 @@ -369,15 +375,18 @@ static int upstream_bridge_distance(struct pci_dev *provider, dist_a++; } + if (dist) + *dist = dist_a + dist_b; + /* * Allow the connection if both devices are on a whitelisted root * complex, but add an arbitrary large value to the distance. */ if (root_complex_whitelist(provider) && root_complex_whitelist(client)) - return 0x1000 + dist_a + dist_b; + return PCI_P2PDMA_MAP_THRU_HOST_BRIDGE; - return -1; + return PCI_P2PDMA_MAP_NOT_SUPPORTED; check_b_path_acs: bb = b; @@ -394,33 +403,44 @@ static int upstream_bridge_distance(struct pci_dev *provider, bb = pci_upstream_bridge(bb); } - if (acs_cnt) - return -2; + if (dist) + *dist = dist_a + dist_b; - return dist_a + dist_b; + if (acs_cnt) { + if (acs_redirects) + *acs_redirects = true; + + return PCI_P2PDMA_MAP_NOT_SUPPORTED; + } + + return PCI_P2PDMA_MAP_BUS_ADDR; } -static int upstream_bridge_distance_warn(struct pci_dev *provider, - struct pci_dev *client) +static enum pci_p2pdma_map_type +upstream_bridge_distance_warn(struct pci_dev *provider, struct pci_dev *client, + int *dist) { struct seq_buf acs_list; + bool acs_redirects; int ret; seq_buf_init(&acs_list, kmalloc(PAGE_SIZE, GFP_KERNEL), PAGE_SIZE); if (!acs_list.buffer) return -ENOMEM; - ret = upstream_bridge_distance(provider, client, &acs_list); - if (ret == -2) { - pci_warn(client, "cannot be used for peer-to-peer DMA as ACS redirect is set between the client and provider (%s)\n", + ret = upstream_bridge_distance(provider, client, dist, &acs_redirects, + &acs_list); + if (acs_redirects) { + 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); + } - } else if (ret < 0) { - pci_warn(client, "cannot be used for peer-to-peer DMA as the client and provider (%s) do not share an upstream bridge\n", + 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)); } @@ -452,7 +472,8 @@ int pci_p2pdma_distance_many(struct pci_dev *provider, struct device **clients, { bool not_supported = false; struct pci_dev *pci_client; - int distance = 0; + int total_dist = 0; + int distance; int i, ret; if (num_clients == 0) @@ -477,26 +498,26 @@ int pci_p2pdma_distance_many(struct pci_dev *provider, struct device **clients, if (verbose) ret = upstream_bridge_distance_warn(provider, - pci_client); + pci_client, &distance); else ret = upstream_bridge_distance(provider, pci_client, - NULL); + &distance, NULL, NULL); pci_dev_put(pci_client); - if (ret < 0) + if (ret == PCI_P2PDMA_MAP_NOT_SUPPORTED) not_supported = true; if (not_supported && !verbose) break; - distance += ret; + total_dist += distance; } if (not_supported) return -1; - return distance; + return total_dist; } EXPORT_SYMBOL_GPL(pci_p2pdma_distance_many); -- 2.20.1
