Re: [PATCH v5 02/10] iommu/vt-d: Use per-device dma_ops

[Christoph Hellwig]

On Fri, Jul 26, 2019 at 09:56:51AM +0800, Lu Baolu wrote:
> I think current code doesn't do the right thing. The user asks the iommu
> driver to use identity domain for a device, but the driver force it back
> to DMA domain because of the device address capability.
>
>> expensive.  I don't think that this change is a good idea, and even if
>> we decide that this is a good idea after all that should be done in a
>> separate prep patch that explains the rationale.
>
> Yes. Make sense.

Now that the bounce code has landed it might be good time to revisit
this patch in isolation and with a better explanation.