On Wed, Feb 16, 2022 at 02:05:41PM -0800, Rajat Jain wrote: > 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. Windows documents the > property to apply to PCIe root ports only. Extend it to apply to any > PCI device. 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 <rajatja@xxxxxxxxxx> > --- > v3: * Use Microsoft's documented property "DmaProperty" > * Resctrict to ACPI only > > drivers/pci/pci-acpi.c | 18 ++++++++++++++++++ > 1 file changed, 18 insertions(+) > > diff --git a/drivers/pci/pci-acpi.c b/drivers/pci/pci-acpi.c > index a42dbf448860..660baa60c040 100644 > --- a/drivers/pci/pci-acpi.c > +++ b/drivers/pci/pci-acpi.c > @@ -1350,12 +1350,30 @@ 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; > + > + /* > + * Microsoft Windows uses this property, and is documented here: > + * https://docs.microsoft.com/en-us/windows-hardware/drivers/pci/dsd-for-pcie-root-ports > + * While Microsoft documents this property as only applicable to PCIe > + * root ports, we expand it to be applicable to any PCI device. > + */ > + if (device_property_read_u8(&dev->dev, "DmaProperty", &val)) > + return; Why not continue to only do this for PCIe devices like it is actually being used for? Why expand it? And what driver/device is going to use this? thanks, greg k-h
