linux-kernel - Re: [PATCH v5 02/14] driver core: Add dma_cleanup callback in bus

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Message-ID: <YgJVj/EmzjtR2SKk@kroah.com>
Date:   Tue, 8 Feb 2022 12:35:43 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Lu Baolu <baolu.lu@...ux.intel.com>
Cc:     Jason Gunthorpe <jgg@...dia.com>,
        Christoph Hellwig <hch@...radead.org>,
        Joerg Roedel <joro@...tes.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        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 02/14] driver core: Add dma_cleanup callback in
 bus_type

On Tue, Feb 08, 2022 at 01:55:29PM +0800, Lu Baolu wrote:
> Hi Greg,
> 
> On 1/4/22 9:04 PM, Greg Kroah-Hartman wrote:
> > On Tue, Jan 04, 2022 at 08:39:11AM -0400, Jason Gunthorpe wrote:
> > > On Tue, Jan 04, 2022 at 02:08:36AM -0800, Christoph Hellwig wrote:
> > > > All these bus callouts still looks horrible and just create tons of
> > > > boilerplate code.
> > > 
> > > Yes, Lu - Greg asked questions then didn't respond to their answers
> > > meaning he accepts them, you should stick with the v4 version.
> > 
> > Trying to catch up on emails from the break, that was way down my list
> > of things to get back to as it's messy and non-obvious.  I'll revisit it
> > again after 5.17-rc1 is out, this is too late for that merge window
> > anyway.
> 
> In this series we want to add calls into the iommu subsystem during
> device driver binding/unbinding, so that the device DMA ownership
> conflict (kernel driver vs. user-space) could be detected and avoided
> before calling into device driver's .probe().
> 
> In this v5 series, we implemented this in the affected buses (amba/
> platform/fsl-mc/pci) which are known to support assigning devices to
> user space through the vfio framework currently. And more buses are
> possible to be affected in the future if they also want to support
> device assignment. Christoph commented that this will create boilerplate
> code in various bus drivers.
> 
> Back to v4 of this series (please refer to below link [1]), we added
> this call in the driver core if buses have provided the dma_configure()
> callback (please refer to below link [2]).
> 
> Which would you prefer, or any other suggestions? We need your guide to
> move this series ahead. Please help to suggest.
> 
> [1] https://lore.kernel.org/linux-iommu/20211217063708.1740334-1-baolu.lu@linux.intel.com/
> [2] https://lore.kernel.org/linux-iommu/20211217063708.1740334-3-baolu.lu@linux.intel.com/

Let me look over the series again this afternooon.

thanks,

greg k-h