The "DmaProperty" is supported and documented by Microsoft here:
https://docs.microsoft.com/en-us/windows-hardware/drivers/pci/dsd-for-pcie-root-ports
They use this property for DMA protection:
https://docs.microsoft.com/en-us/windows/security/information-protection/kernel-dma-protection-for-thunderbolt
Support the "DmaProperty" with the same semantics. This is useful for
internal PCI devices that do not hang off a PCIe rootport, but offer
an attack surface for DMA attacks (e.g. internal network devices).
Signed-off-by: Rajat Jain <raja...@google.com>
---
v4: * Add the GUID.
* Use the (now) renamed property - pci_dev->poses_dma_risk)
* Update the comment and commitlog.
v3: * Use Microsoft's documented property "DmaProperty"
* Resctrict to ACPI only
drivers/acpi/property.c | 3 +++
drivers/pci/pci-acpi.c | 16 ++++++++++++++++
2 files changed, 19 insertions(+)
diff --git a/drivers/acpi/property.c b/drivers/acpi/property.c
index d0986bda2964..20603cacc28d 100644
--- a/drivers/acpi/property.c
+++ b/drivers/acpi/property.c
@@ -48,6 +48,9 @@ static const guid_t prp_guids[] = {
/* Storage device needs D3 GUID: 5025030f-842f-4ab4-a561-99a5189762d0 */
GUID_INIT(0x5025030f, 0x842f, 0x4ab4,
0xa5, 0x61, 0x99, 0xa5, 0x18, 0x97, 0x62, 0xd0),
+ /* DmaProperty for PCI devices GUID:
70d24161-6dd5-4c9e-8070-705531292865 */
+ GUID_INIT(0x70d24161, 0x6dd5, 0x4c9e,
+ 0x80, 0x70, 0x70, 0x55, 0x31, 0x29, 0x28, 0x65),
};
/* ACPI _DSD data subnodes GUID: dbb8e3e6-5886-4ba6-8795-1319f52a966b */
diff --git a/drivers/pci/pci-acpi.c b/drivers/pci/pci-acpi.c
index 1f15ab7eabf8..5360f1af2ed3 100644
--- a/drivers/pci/pci-acpi.c
+++ b/drivers/pci/pci-acpi.c
@@ -1350,12 +1350,28 @@ static void pci_acpi_set_external_facing(struct pci_dev
*dev)
dev->external_facing = 1;
}
+static void pci_acpi_check_for_dma_protection(struct pci_dev *dev)
+{
+ u8 val;
+
+ /*
+ * Property also used by Microsoft Windows for same purpose,
+ * (to implement DMA protection from a device, using the IOMMU).
+ */
+ if (device_property_read_u8(&dev->dev, "DmaProperty", &val))
+ return;
+
+ if (val)
+ dev->poses_dma_risk = 1;
+}
+
void pci_acpi_setup(struct device *dev, struct acpi_device *adev)
{
struct pci_dev *pci_dev = to_pci_dev(dev);
pci_acpi_optimize_delay(pci_dev, adev->handle);
pci_acpi_set_external_facing(pci_dev);
+ pci_acpi_check_for_dma_protection(pci_dev);
pci_acpi_add_edr_notifier(pci_dev);
pci_acpi_add_pm_notifier(adev, pci_dev);
--
2.35.1.894.gb6a874cedc-goog
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