From 1af7c26c59ebcf241e865dd16dcc251e61472a37 Mon Sep 17 00:00:00 2001 From: Shlomo Pongratz Date: Sun, 10 Apr 2022 13:52:13 +0300 Subject: [PATCH] PCI/P2PDMA: Whitelist Intel Skylake-E Root Ports at any devfn In 7b94b53db34f ("PCI/P2PDMA: Add Intel Sky Lake-E Root Ports B, C, D to the whitelist"), Andrew Maier added Skylake-E 2031, 2032, and 2033 Root Ports to the pci_p2pdma_whitelist[], so we assume P2PDMA between devices below these ports works. Previously we only checked the whitelist for a device at devfn 00.0 on the root bus, which is often a "host bridge". But these Skylake Root Ports may be at any devfn and there may be no "host bridge" device. Generalize pci_host_bridge_dev() so we check the first device on the root bus, whether it is devfn 00.0 or a PCIe Root Port, against the whitelist. [bhelgaas: commit log, comment] Link: https://lore.kernel.org/r/20220410105213.690-2-shlomop@pliops.com Tested-by: Maor Gottlieb Signed-off-by: Shlomo Pongratz Signed-off-by: Bjorn Helgaas Cc: Andrew Maier --- drivers/pci/p2pdma.c | 25 +++++++++++++++---------- 1 file changed, 15 insertions(+), 10 deletions(-) diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c index 30b1df3c9d2f..462b429ad243 100644 --- a/drivers/pci/p2pdma.c +++ b/drivers/pci/p2pdma.c @@ -326,15 +326,16 @@ static const struct pci_p2pdma_whitelist_entry { }; /* - * This lookup function tries to find the PCI device corresponding to a given - * host bridge. + * If the first device on host's root bus is either devfn 00.0 or a PCIe + * Root Port, return it. Otherwise return NULL. * - * It assumes the host bridge device is the first PCI device in the - * bus->devices list and that the devfn is 00.0. These assumptions should hold - * for all the devices in the whitelist above. + * We often use a devfn 00.0 "host bridge" in the pci_p2pdma_whitelist[] + * (though there is no PCI/PCIe requirement for such a device). On some + * platforms, e.g., Intel Skylake, there is no such host bridge device, and + * pci_p2pdma_whitelist[] may contain a Root Port at any devfn. * - * This function is equivalent to pci_get_slot(host->bus, 0), however it does - * not take the pci_bus_sem lock seeing __host_bridge_whitelist() must not + * This function is similar to pci_get_slot(host->bus, 0), but it does + * not take the pci_bus_sem lock since __host_bridge_whitelist() must not * sleep. * * For this to be safe, the caller should hold a reference to a device on the @@ -350,10 +351,14 @@ static struct pci_dev *pci_host_bridge_dev(struct pci_host_bridge *host) if (!root) return NULL; - if (root->devfn != PCI_DEVFN(0, 0)) - return NULL; - return root; + if (root->devfn == PCI_DEVFN(0, 0)) + return root; + + if (pci_pcie_type(root) == PCI_EXP_TYPE_ROOT_PORT) + return root; + + return NULL; } static bool __host_bridge_whitelist(struct pci_host_bridge *host,