On Fri, Feb 18, 2022 at 08:55:14AM +0800, Lu Baolu wrote: > The devices on platform/amba/fsl-mc/PCI buses could be bound to drivers > with the device DMA managed by kernel drivers or user-space applications. > Unfortunately, multiple devices may be placed in the same IOMMU group > because they cannot be isolated from each other. The DMA on these devices > must either be entirely under kernel control or userspace control, never > a mixture. Otherwise the driver integrity is not guaranteed because they > could access each other through the peer-to-peer accesses which by-pass > the IOMMU protection. > > This checks and sets the default DMA mode during driver binding, and > cleanups during driver unbinding. In the default mode, the device DMA is > managed by the device driver which handles DMA operations through the > kernel DMA APIs (see Documentation/core-api/dma-api.rst). > > For cases where the devices are assigned for userspace control through the > userspace driver framework(i.e. VFIO), the drivers(for example, vfio_pci/ > vfio_platfrom etc.) may set a new flag (driver_managed_dma) to skip this > default setting in the assumption that the drivers know what they are > doing with the device DMA. > > With the IOMMU layer knowing DMA ownership of each device, above problem > can be solved. > > Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> > Cc: Bjorn Helgaas <bhelgaas@xxxxxxxxxx> > Cc: Stuart Yoder <stuyoder@xxxxxxxxx> > Cc: Laurentiu Tudor <laurentiu.tudor@xxxxxxx> > Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx> > --- > include/linux/amba/bus.h | 8 ++++++++ > include/linux/fsl/mc.h | 8 ++++++++ > include/linux/pci.h | 8 ++++++++ > include/linux/platform_device.h | 8 ++++++++ > drivers/amba/bus.c | 20 ++++++++++++++++++++ > drivers/base/platform.c | 20 ++++++++++++++++++++ > drivers/bus/fsl-mc/fsl-mc-bus.c | 26 ++++++++++++++++++++++++-- > drivers/pci/pci-driver.c | 21 +++++++++++++++++++++ > 8 files changed, 117 insertions(+), 2 deletions(-) For the platform.c stuff: Reviewed-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> thanks for renaming this. greg k-h
