Re: [PATCH v5 10/13] nvme-pci: Add support for P2P memory in requests

[Logan Gunthorpe]

On 04/09/18 09:16 AM, Jason Gunthorpe wrote:
>>  	if (iod->nents) {
>> -		dma_unmap_sg(dev->dev, iod->sg, iod->nents, dma_dir);
>> +		/* P2PDMA requests do not need to be unmapped */
>> +		if (!is_pci_p2pdma_page(sg_page(iod->sg)))
>> +			dma_unmap_sg(dev->dev, iod->sg, iod->nents, dma_dir);
> 
> This seems like a poor direction, if we add IOMMU hairpin support we
> will need unmapping.

It can always be added later. In any case, you'll have to convince
Christoph who requested the change; I'm not that invested in this decision.

Logan