Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Received-SPF: Pass (protection.outlook.com: domain of nvidia.com designates
 216.228.112.34 as permitted sender) receiver=protection.outlook.com;
 client-ip=216.228.112.34; helo=mail.nvidia.com;
Subject: Re: [PATCH 04/16] PCI/P2PDMA: Refactor pci_p2pdma_map_type() to take
 pagmap and device
To:     Jason Gunthorpe <jgg@ziepe.ca>
CC:     Logan Gunthorpe <logang@deltatee.com>,
        <linux-kernel@vger.kernel.org>, <linux-nvme@lists.infradead.org>,
        <linux-block@vger.kernel.org>, <linux-pci@vger.kernel.org>,
        <linux-mm@kvack.org>, <iommu@lists.linux-foundation.org>,
        Stephen Bates <sbates@raithlin.com>,
        Christoph Hellwig <hch@lst.de>,
        Dan Williams <dan.j.williams@intel.com>,
        =?UTF-8?Q?Christian_K=c3=b6nig?= <christian.koenig@amd.com>,
        Don Dutile <ddutile@redhat.com>,
        Matthew Wilcox <willy@infradead.org>,
        Daniel Vetter <daniel.vetter@ffwll.ch>,
        Jakowski Andrzej <andrzej.jakowski@intel.com>,
        Minturn Dave B <dave.b.minturn@intel.com>,
        Jason Ekstrand <jason@jlekstrand.net>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Xiong Jianxin <jianxin.xiong@intel.com>,
        Bjorn Helgaas <helgaas@kernel.org>,
        Ira Weiny <ira.weiny@intel.com>,
        Robin Murphy <robin.murphy@arm.com>
References: <20210408170123.8788-1-logang@deltatee.com>
 <20210408170123.8788-5-logang@deltatee.com>
 <ce04d398-e4a1-b3aa-2a4e-b1b868470144@nvidia.com>
 <f719ba91-07ba-c703-2dc9-32cb1214e9c0@deltatee.com>
 <f07f0ca7-9772-5b3b-4cea-9defcefaaf8b@nvidia.com>
 <ab0e4256-79c9-c181-5aec-f6869a92a80c@deltatee.com>
 <d4f19947-d4c1-451b-311f-9e31a4ded6fc@nvidia.com>
 <20210503225705.GA2047089@ziepe.ca>
From:   John Hubbard <jhubbard@nvidia.com>
Message-ID: <4fd9381a-d9aa-31fe-c1d8-660e2dbaab62@nvidia.com>
Date:   Mon, 3 May 2021 16:40:02 -0700
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101
 Thunderbird/78.10.0
MIME-Version: 1.0
In-Reply-To: <20210503225705.GA2047089@ziepe.ca>
Content-Type: text/plain; charset="utf-8"; format=flowed
Content-Language: en-US
Content-Transfer-Encoding: 7bit
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 03 May 2021 23:40:03.8504
 (UTC)
X-MS-Exchange-CrossTenant-Network-Message-Id: deea838f-aa53-493e-1b57-08d90e8cc6a1
X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a
X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.112.34];Helo=[mail.nvidia.com]
X-MS-Exchange-CrossTenant-AuthSource: BN8NAM11FT049.eop-nam11.prod.protection.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Anonymous
X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem
X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR12MB4629
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

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