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| author | Christian König <ckoenig.leichtzumerken@gmail.com> | 2019-04-18 13:58:59 +0200 |
|---|---|---|
| committer | Bjorn Helgaas <bhelgaas@google.com> | 2019-05-01 16:53:39 -0500 |
| commit | 0f97da83102610db886e8b688b9029e080e6d511 (patch) | |
| tree | f76f4b8095249e8266ca231ff82c5aceaa530477 /drivers | |
| parent | 9e98c678c2d6ae3a17cb2de55d17f69dddaa231b (diff) | |
| download | linux-0f97da83102610db886e8b688b9029e080e6d511.tar.bz2 | |
PCI/P2PDMA: Allow P2P DMA between any devices under AMD ZEN Root Complex
The PCI specs say that peer-to-peer DMA should be supported between any two
devices that have a common upstream PCI-to-PCI bridge. But devices under
different Root Ports don't share a common upstream bridge, and PCIe r4.0,
sec 1.3.1, says routing peer-to-peer transactions between Root Ports in the
same Root Complex is optional.
Many Root Complexes, including AMD ZEN, *do* support peer-to-peer DMA even
between Root Ports. Add a whitelist and allow peer-to-peer DMA if both
participants are attached to a Root Complex known to support it.
Link: https://lore.kernel.org/linux-pci/20190418115859.2394-1-christian.koenig@amd.com
Signed-off-by: Christian König <christian.koenig@amd.com>
[bhelgaas: changelog]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/pci/p2pdma.c | 38 |
1 files changed, 35 insertions, 3 deletions
diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c index c52298d76e64..742928d0053e 100644 --- a/drivers/pci/p2pdma.c +++ b/drivers/pci/p2pdma.c @@ -275,6 +275,30 @@ static void seq_buf_print_bus_devfn(struct seq_buf *buf, struct pci_dev *pdev) } /* + * If we can't find a common upstream bridge take a look at the root + * complex and compare it to a whitelist of known good hardware. + */ +static bool root_complex_whitelist(struct pci_dev *dev) +{ + struct pci_host_bridge *host = pci_find_host_bridge(dev->bus); + struct pci_dev *root = pci_get_slot(host->bus, PCI_DEVFN(0, 0)); + unsigned short vendor, device; + + if (!root) + return false; + + vendor = root->vendor; + device = root->device; + pci_dev_put(root); + + /* AMD ZEN host bridges can do peer to peer */ + if (vendor == PCI_VENDOR_ID_AMD && device == 0x1450) + return true; + + return false; +} + +/* * Find the distance through the nearest common upstream bridge between * two PCI devices. * @@ -317,13 +341,13 @@ static void seq_buf_print_bus_devfn(struct seq_buf *buf, struct pci_dev *pdev) * 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 *a, - struct pci_dev *b, +static int upstream_bridge_distance(struct pci_dev *provider, + struct pci_dev *client, struct seq_buf *acs_list) { + struct pci_dev *a = provider, *b = client, *bb; int dist_a = 0; int dist_b = 0; - struct pci_dev *bb = NULL; int acs_cnt = 0; /* @@ -354,6 +378,14 @@ static int upstream_bridge_distance(struct pci_dev *a, dist_a++; } + /* + * Allow the connection if both devices are on a whitelisted root + * complex, but add an arbitary large value to the distance. + */ + if (root_complex_whitelist(provider) && + root_complex_whitelist(client)) + return 0x1000 + dist_a + dist_b; + return -1; check_b_path_acs: |