[RFC] virtio: Use DMA MAP API for devices without an IOMMU

Anshuman Khandual khandual at linux.vnet.ibm.com
Fri Apr 6 12:53:10 AEST 2018


On 04/06/2018 02:48 AM, Benjamin Herrenschmidt wrote:
> On Thu, 2018-04-05 at 21:34 +0300, Michael S. Tsirkin wrote:
>>> In this specific case, because that would make qemu expect an iommu,
>>> and there isn't one.
>>
>>
>> I think that you can set iommu_platform in qemu without an iommu.
> 
> No I mean the platform has one but it's not desirable for it to be used
> due to the performance hit.

Also the only requirement is to bounce the I/O buffers through SWIOTLB
implemented as DMA API which the virtio core understands. There is no
need for an IOMMU to be involved for the device representation in this
case IMHO.



More information about the Linuxppc-dev mailing list