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PCI/P2PDMA: Whitelist Intel Skylake-E Root Ports at any devfn

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In 7b94b53db3 ("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 <maorg@nvidia.com>
Signed-off-by: Shlomo Pongratz <shlomop@pliops.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: Andrew Maier <andrew.maier@eideticom.com>
This commit is contained in:
Shlomo Pongratz 2022-04-10 13:52:13 +03:00 committed by Bjorn Helgaas
parent 3123109284
commit 1af7c26c59
1 changed files with 15 additions and 10 deletions
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25
drivers/pci/p2pdma.c
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@ -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,