Messages in this thread | | | Subject | Re: [PATCH v5 01/14] iommu: Add dma ownership management interfaces | From | Lu Baolu <> | Date | Thu, 6 Jan 2022 11:43:25 +0800 |
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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
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