linux-kernel - Re: [PATCH v6] vfio/cdx: add support for CDX bus

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Message-ID: <ZHin0Redl/YIgNFg@ziepe.ca>
Date:   Thu, 1 Jun 2023 11:14:41 -0300
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Nipun Gupta <nipun.gupta@....com>
Cc:     Alex Williamson <alex.williamson@...hat.com>,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        masahiroy@...nel.org, nathan@...nel.org, ndesaulniers@...gle.com,
        nicolas@...sle.eu, git@....com, harpreet.anand@....com,
        pieter.jansen-van-vuuren@....com, nikhil.agarwal@....com,
        michal.simek@....com
Subject: Re: [PATCH v6] vfio/cdx: add support for CDX bus

On Mon, May 29, 2023 at 01:36:30PM +0530, Nipun Gupta wrote:
> 
> 
> On 5/25/2023 1:18 AM, Alex Williamson wrote:
> > 
> > On Wed, 24 May 2023 10:45:29 -0600
> > Alex Williamson <alex.williamson@...hat.com> wrote:
> > 
> > > On Wed, 17 May 2023 15:27:18 +0530
> > > Nipun Gupta <nipun.gupta@....com> wrote:
> > > 
> 
> <snip>
> 
> > > > +
> > > > +MODULE_DEVICE_TABLE(cdx, vfio_cdx_table);
> > > > +
> > > > +static struct cdx_driver vfio_cdx_driver = {
> > > > +   .probe          = vfio_cdx_probe,
> > > > +   .remove         = vfio_cdx_remove,
> > > > +   .match_id_table = vfio_cdx_table,
> > > > +   .driver = {
> > > > +           .name   = "vfio-cdx",
> > > > +           .owner  = THIS_MODULE,
> > > > +   },
> > > > +   .driver_managed_dma = true,
> > 
> > Hmm, looks like cdx bus is broken here, there's no actual
> > implementation of a dma_configure callback and no setup of the IOMMU
> > default domain for theoretical cdx drivers that might want to use the
> > DMA API.  Without that, this driver_manged_dma flag doesn't provide any
> > guarantees to a vfio driver that we have exclusive ownership of the
> > group.  Please fix, this flag needs to actually have some meaning on
> > cdx.  Thanks,
> > 
> > Alex
> 
> Agree, this change was missed on CDX bus and we are working on fixing this.
> Shall I send this fix as a commit with this patch?

You should send it as a rc fixup for your already merged CDX bus stuff

Jason