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From:   Logan Gunthorpe <logang@deltatee.com>
Message-ID: <d5548f5d-59df-f38e-255d-59b46a17a219@deltatee.com>
Date:   Tue, 4 Sep 2018 09:47:07 -0600
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Subject: Re: [PATCH v5 10/13] nvme-pci: Add support for P2P memory in requests
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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