Re: [PATCH v2 09/16] driver core: add iommu device fault reporting data

[Christoph Hellwig]

On Thu, Oct 05, 2017 at 04:03:37PM -0700, Jacob Pan wrote:
> DMA faults can be detected by IOMMU at device level. Adding a pointer
> to struct device allows IOMMU subsystem to report relevant faults
> back to the device driver for further handling.
> For direct assigned device (or user space drivers), guest OS holds
> responsibility to handle and respond per device IOMMU fault.
> Therefore we need fault reporting mechanism to propagate faults beyond
> IOMMU subsystem.

We use struct device all over the system, and I don't think we should
bloat it for fringe case IOMMU bits.

Someone really needs to take a step back and figure out how to move
this into a structure that's only allocated for device that actually
can do physical DMA (and/or have an iommu attached)

This is the 3rd iommu field, in addition to 8 dma-specific fields
that we carry around for each struct device.