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Date:   Mon, 20 Jan 2020 09:55:00 +0100
From:   Cornelia Huck <cohuck@redhat.com>
To:     "Liu, Yi L" <yi.l.liu@intel.com>
Cc:     "alex.williamson@redhat.com" <alex.williamson@redhat.com>,
        "kwankhede@nvidia.com" <kwankhede@nvidia.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
        "Tian, Kevin" <kevin.tian@intel.com>,
        "joro@8bytes.org" <joro@8bytes.org>,
        "peterx@redhat.com" <peterx@redhat.com>,
        "baolu.lu@linux.intel.com" <baolu.lu@linux.intel.com>,
        Masahiro Yamada <yamada.masahiro@socionext.com>
Subject: Re: [PATCH v4 11/12] samples: add vfio-mdev-pci driver
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On Sat, 18 Jan 2020 14:23:45 +0000
"Liu, Yi L" <yi.l.liu@intel.com> wrote:

> > From: Cornelia Huck [mailto:cohuck@redhat.com]
> > Sent: Friday, January 17, 2020 1:40 AM
> > To: Liu, Yi L <yi.l.liu@intel.com>
> > Subject: Re: [PATCH v4 11/12] samples: add vfio-mdev-pci driver
> > 
> > On Thu, 16 Jan 2020 13:23:28 +0000
> > "Liu, Yi L" <yi.l.liu@intel.com> wrote:
> >   
> > > > From: Cornelia Huck [mailto:cohuck@redhat.com]
> > > > Sent: Wednesday, January 15, 2020 8:30 PM
> > > > To: Liu, Yi L <yi.l.liu@intel.com>
> > > > Subject: Re: [PATCH v4 11/12] samples: add vfio-mdev-pci driver
> > > >
> > > > On Tue,  7 Jan 2020 20:01:48 +0800
> > > > Liu Yi L <yi.l.liu@intel.com> wrote:  
> >   
> > > > > diff --git a/samples/Kconfig b/samples/Kconfig index
> > > > > 9d236c3..50d207c 100644
> > > > > --- a/samples/Kconfig
> > > > > +++ b/samples/Kconfig
> > > > > @@ -190,5 +190,15 @@ config SAMPLE_INTEL_MEI
> > > > >  	help
> > > > >  	  Build a sample program to work with mei device.
> > > > >
> > > > > +config SAMPLE_VFIO_MDEV_PCI
> > > > > +	tristate "Sample driver for wrapping PCI device as a mdev"
> > > > > +	select VFIO_PCI_COMMON
> > > > > +	select VFIO_PCI  
> > > >
> > > > Why does this still need to select VFIO_PCI? Shouldn't all needed
> > > > infrastructure rather be covered by VFIO_PCI_COMMON already?  
> > >
> > > VFIO_PCI_COMMON is supposed to be the dependency of both VFIO_PCI and
> > > SAMPLE_VFIO_MDEV_PCI. However, the source code of VFIO_PCI_COMMON are
> > > under drivers/vfio/pci which is compiled per the configuration of VFIO_PCI.
> > > Besides of letting SAMPLE_VFIO_MDEV_PCI select VFIO_PCI, I can also
> > > add a line in drivers/vfio/Makefile to make the source code under
> > > drivers/vfio/pci to be compiled when either VFIO_PCI or
> > > VFIO_PCI_COMMON are configed. But I'm afraid it is a bit ugly. So I
> > > choose to let SAMPLE_VFIO_MDEV_PCI select VFIO_PCI. If you have other
> > > idea, I would be pleased to know it. :-)  
> > 
> > Shouldn't building drivers/vfio/pci/ for CONFIG_VFIO_PCI_COMMON already be
> > enough (the Makefile changes look fine to me)? Or am I missing something obvious?  
> 
> The problem is in the drivers/vfio/Makefile. If CONFIG_VFIO_PCI is not
> selected then the pci/ directory is not compiled. Even CONFIG_VFIO_PCI=M,
> it will throw error if SAMPLE_VFIO_MDEV_PCI=y. So I let SAMPLE_VFIO_MDEV_PCI
> select CONFIG_VFIO_PCI all the same. I'm not sure if this is good. Or maybe
> there is better way to ensure pci/ is compiled.
> 
> # SPDX-License-Identifier: GPL-2.0
> vfio_virqfd-y := virqfd.o
> 
> obj-$(CONFIG_VFIO) += vfio.o
> obj-$(CONFIG_VFIO_VIRQFD) += vfio_virqfd.o
> obj-$(CONFIG_VFIO_IOMMU_TYPE1) += vfio_iommu_type1.o
> obj-$(CONFIG_VFIO_IOMMU_SPAPR_TCE) += vfio_iommu_spapr_tce.o
> obj-$(CONFIG_VFIO_SPAPR_EEH) += vfio_spapr_eeh.o
> obj-$(CONFIG_VFIO_PCI) += pci/

That's actually what I meant: s/CONFIG_VFIO_PCI/CONFIG_VFIO_PCI_COMMON/ here.

> obj-$(CONFIG_VFIO_PLATFORM) += platform/
> obj-$(CONFIG_VFIO_MDEV) += mdev/
> 
> Thanks,
> Yi Liu
>