Hi Bjorn,
On 1/5/22 12:41 AM, Bjorn Helgaas wrote:
This adds dma ownership management in iommu core and exposes several
interfaces for the device drivers and the device userspace assignment
framework (i.e. vfio), so that any conflict between user and kernel
controlled DMA could be detected at the beginning.
Maybe I'm missing the point because I don't know what "conflict
between user and kernel controlled DMA" is. Are you talking about
both userspace and the kernel programming the same device to do DMA?
It's about both userspace and kernel programming different devices
belonging to a same iommu group to do DMA. For example, PCI device A and
B sit in a some iommu group. Userspace programs device A for DMA and a
kernel driver programs device B. Userspace may intentionally or
unintentionally program device A to access and change device B's MMIO
with P2P DMA transactions which cause the kernel driver for device B
result in an inconsistent state.
This may not be all, just an example.
Best regards,
baolu
