linux-kernel - Re: [PATCH v5 07/14] PCI: Add driver dma ownership management

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Message-ID: <ee9c2210-f718-223f-c678-038d3ea4a93e@linux.intel.com>
Date:   Tue, 15 Feb 2022 11:06:54 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     Jason Gunthorpe <jgg@...dia.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     baolu.lu@...ux.intel.com, Joerg Roedel <joro@...tes.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Christoph Hellwig <hch@...radead.org>,
        Kevin Tian <kevin.tian@...el.com>,
        Ashok Raj <ashok.raj@...el.com>, Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Dan Williams <dan.j.williams@...el.com>, rafael@...nel.org,
        Diana Craciun <diana.craciun@....nxp.com>,
        Cornelia Huck <cohuck@...hat.com>,
        Eric Auger <eric.auger@...hat.com>,
        Liu Yi L <yi.l.liu@...el.com>,
        Jacob jun Pan <jacob.jun.pan@...el.com>,
        Chaitanya Kulkarni <kch@...dia.com>,
        Stuart Yoder <stuyoder@...il.com>,
        Laurentiu Tudor <laurentiu.tudor@....com>,
        Thierry Reding <thierry.reding@...il.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Li Yang <leoyang.li@....com>,
        Dmitry Osipenko <digetx@...il.com>,
        iommu@...ts.linux-foundation.org, linux-pci@...r.kernel.org,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 07/14] PCI: Add driver dma ownership management

On 2/14/22 9:43 PM, Jason Gunthorpe wrote:
> On Mon, Feb 14, 2022 at 02:39:18PM +0100, Greg Kroah-Hartman wrote:
> 
>>> A driver that sets this flag can still decide to enable the dma API on
>>> its own. eg tegra drivers do this.
>>
>> So you are just forcing the driver to manage this all on their own, so
>> how about, "driver_managed_dma", or even shorter "managed_dma"?
> 
> Yeah, I like "driver_managed_dma" alot, it captures the entire idea

This makes a lot of sense. For most drivers, they don't need to care
about this flag as all DMAs are handled through the kernel DMA API. For
VFIO or similar drivers, they know how to manage the DMA themselves and
set this flag so that the IOMMU layer will allow them to setup and
manage their own I/O address space.

If there is no better naming, I'd like to use this and add some comments
for device drivers developers.

Thanks a lot to Greg and Jason.

Best regards,
baolu