linux-kernel - Re: [PATCH 04/16] PCI/P2PDMA: Refactor pci_p2pdma_map

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Date:   Mon, 3 May 2021 16:40:02 -0700
From:   John Hubbard <jhubbard@...dia.com>
To:     Jason Gunthorpe <jgg@...pe.ca>
CC:     Logan Gunthorpe <logang@...tatee.com>,
        <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>,
        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 04/16] PCI/P2PDMA: Refactor pci_p2pdma_map_type() to take
 pagmap and device

On 5/3/21 3:57 PM, Jason Gunthorpe wrote:
> On Mon, May 03, 2021 at 02:54:26PM -0700, John Hubbard wrote:
> 
>> I guess my main concern here is that there are these pci*() functions
>> that somehow want to pass around struct device.
> 
> Well, this is the main issue - helpers being used inside IOMMU code
> should not be called pci* functions. This is some generic device p2p
> interface that happens to only support PCI to PCI transfers today.
> 

Yes, maybe renaming a few levels of functions would help at least clarify
what the code can do. Once the code reaches layers that truly are
PCI-specific, that's where it should transition to using pci_dev args,
and that's also where it should return -ENOTSUPP back up the calling
stack.

thanks,
-- 
John Hubbard
NVIDIA