linux-kernel - Re: [PATCH 14/16] nvme-rdma: Ensure dma support when using p2pdma

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Date:   Tue, 27 Apr 2021 16:59:57 -0600
From:   Logan Gunthorpe <logang@...tatee.com>
To:     Jason Gunthorpe <jgg@...pe.ca>
Cc:     linux-kernel@...r.kernel.org, linux-nvme@...ts.infradead.org,
        linux-block@...r.kernel.org, linux-pci@...r.kernel.org,
        linux-mm@...ck.org, iommu@...ts.linux-foundation.org,
        Stephen Bates <sbates@...thlin.com>,
        Christoph Hellwig <hch@....de>,
        Dan Williams <dan.j.williams@...el.com>,
        Christian König <christian.koenig@....com>,
        John Hubbard <jhubbard@...dia.com>,
        Don Dutile <ddutile@...hat.com>,
        Matthew Wilcox <willy@...radead.org>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Jakowski Andrzej <andrzej.jakowski@...el.com>,
        Minturn Dave B <dave.b.minturn@...el.com>,
        Jason Ekstrand <jason@...kstrand.net>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Xiong Jianxin <jianxin.xiong@...el.com>,
        Bjorn Helgaas <helgaas@...nel.org>,
        Ira Weiny <ira.weiny@...el.com>,
        Robin Murphy <robin.murphy@....com>
Subject: Re: [PATCH 14/16] nvme-rdma: Ensure dma support when using p2pdma



On 2021-04-27 1:47 p.m., Jason Gunthorpe wrote:
> On Thu, Apr 08, 2021 at 11:01:21AM -0600, Logan Gunthorpe wrote:
>> Ensure the dma operations support p2pdma before using the RDMA
>> device for P2PDMA. This allows switching the RDMA driver from
>> pci_p2pdma_map_sg() to dma_map_sg_p2pdma().
>>
>> Signed-off-by: Logan Gunthorpe <logang@...tatee.com>
>>  drivers/nvme/target/rdma.c | 3 ++-
>>  1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/nvme/target/rdma.c b/drivers/nvme/target/rdma.c
>> index 6c1f3ab7649c..3ec7e77e5416 100644
>> +++ b/drivers/nvme/target/rdma.c
>> @@ -414,7 +414,8 @@ static int nvmet_rdma_alloc_rsp(struct nvmet_rdma_device *ndev,
>>  	if (ib_dma_mapping_error(ndev->device, r->send_sge.addr))
>>  		goto out_free_rsp;
>>  
>> -	if (!ib_uses_virt_dma(ndev->device))
>> +	if (!ib_uses_virt_dma(ndev->device) &&
>> +	    dma_pci_p2pdma_supported(&ndev->device->dev))
> 
> ib_uses_virt_dma() should not be called by nvme and this is using the
> wrong device pointer to query for DMA related properties.
> 
> I suspect this wants a ib_dma_pci_p2p_dma_supported() wrapper like
> everything else.

Makes sense. Will add for v2.

Logan