A PCI device is "external_facing" if it's a Root Port with the ACPI "ExternalFacingPort" property or if it has the DT "external-facing" property. We consider everything downstream from such a device to be removable by user. We're mainly concerned with consumer platforms with user accessible thunderbolt ports that are vulnerable to DMA attacks, and we expect those ports to be identified as "ExternalFacingPort". Devices in traditional hotplug slots can technically be removed, but the expectation is that unless the port is marked with "ExternalFacingPort", such devices are less accessible to user / may not be removed by end user, and thus not exposed as "removable" to userspace. Set pci_dev_type.supports_removable so the device core exposes the "removable" file in sysfs, and tell the device core about removable devices. This can be used by userspace to implment any policies it wants to, tailored specifically for user removable devices. Eg usage: https://chromium-review.googlesource.com/c/chromiumos/platform2/+/2591812 https://chromium-review.googlesource.com/c/chromiumos/platform2/+/2795038 (code uses such an attribute to remove external PCI devicces or disable features on them as needed by the policy desired) Signed-off-by: Rajat Jain <rajatja@xxxxxxxxxx> --- v3: - commit log updated - Rename set_pci_dev_removable() -> pci_set_removable() - Call it after applying early PCI quirks. v2: Add documentation Documentation/ABI/testing/sysfs-devices-removable | 3 ++- drivers/pci/pci-sysfs.c | 1 + drivers/pci/probe.c | 12 ++++++++++++ 3 files changed, 15 insertions(+), 1 deletion(-) diff --git a/Documentation/ABI/testing/sysfs-devices-removable b/Documentation/ABI/testing/sysfs-devices-removable index 9dabcad7cdcd..ec0b243f5db4 100644 --- a/Documentation/ABI/testing/sysfs-devices-removable +++ b/Documentation/ABI/testing/sysfs-devices-removable @@ -14,4 +14,5 @@ Description: Currently this is only supported by USB (which infers the information from a combination of hub descriptor bits and - platform-specific data such as ACPI). + platform-specific data such as ACPI) and PCI (which gets this + from ACPI / device tree). diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c index beb8d1f4fafe..38b3259ba333 100644 --- a/drivers/pci/pci-sysfs.c +++ b/drivers/pci/pci-sysfs.c @@ -1541,4 +1541,5 @@ static const struct attribute_group *pci_dev_attr_groups[] = { const struct device_type pci_dev_type = { .groups = pci_dev_attr_groups, + .supports_removable = true, }; diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c index 3a62d09b8869..3515afeeaba8 100644 --- a/drivers/pci/probe.c +++ b/drivers/pci/probe.c @@ -1575,6 +1575,16 @@ static void set_pcie_untrusted(struct pci_dev *dev) dev->untrusted = true; } +static void pci_set_removable(struct pci_dev *dev) +{ + struct pci_dev *parent = pci_upstream_bridge(dev); + if (parent && + (parent->external_facing || dev_is_removable(&parent->dev))) + dev_set_removable(&dev->dev, DEVICE_REMOVABLE); + else + dev_set_removable(&dev->dev, DEVICE_FIXED); +} + /** * pci_ext_cfg_is_aliased - Is ext config space just an alias of std config? * @dev: PCI device @@ -1822,6 +1832,8 @@ int pci_setup_device(struct pci_dev *dev) /* Early fixups, before probing the BARs */ pci_fixup_device(pci_fixup_early, dev); + pci_set_removable(dev); + pci_info(dev, "[%04x:%04x] type %02x class %#08x\n", dev->vendor, dev->device, dev->hdr_type, dev->class); -- 2.31.1.607.g51e8a6a459-goog
