Re: [PATCH v2 10/11] vfio: Make vfio_container optionally compiled

From: Alex Williamson <alex.williamson@redhat.com>
To: Jason Gunthorpe <jgg@nvidia.com>
Cc: kvm@vger.kernel.org, Kevin Tian <kevin.tian@intel.com>,
	dri-devel@lists.freedesktop.org,
	Vineeth Vijayan <vneethv@linux.ibm.com>,
	Diana Craciun <diana.craciun@oss.nxp.com>,
	Alexander Gordeev <agordeev@linux.ibm.com>,
	Longfang Liu <liulongfang@huawei.com>,
	linux-s390@vger.kernel.org, "Liu, Yi L" <yi.l.liu@intel.com>,
	Matthew Rosato <mjrosato@linux.ibm.com>,
	Will Deacon <will@kernel.org>, Joerg Roedel <joro@8bytes.org>,
	Halil Pasic <pasic@linux.ibm.com>,
	iommu@lists.linux.dev, Nicolin Chen <nicolinc@nvidia.com>,
	Christian Borntraeger <borntraeger@linux.ibm.com>,
	intel-gfx@lists.freedesktop.org, Zhi Wang <zhi.a.wang@intel.com>,
	Jason Herne <jjherne@linux.ibm.com>,
	Eric Farman <farman@linux.ibm.com>,
	Vasily Gorbik <gor@linux.ibm.com>,
	Heiko Carstens <hca@linux.ibm.com>,
	Eric Auger <eric.auger@redhat.com>,
	Harald Freudenberger <freude@linux.ibm.com>,
	Rodrigo Vivi <rodrigo.vivi@intel.com>,
	intel-gvt-dev@lists.freedesktop.org,
	Tony Krowiak <akrowiak@linux.ibm.com>,
	Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>,
	Yishai Hadas <yishaih@nvidia.com>,
	Cornelia Huck <cohuck@redhat.com>,
	Peter Oberparleiter <oberpar@linux.ibm.com>,
	Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>,
	Sven Schnelle <svens@linux.ibm.com>,
	Robin Murphy <robin.murphy@arm.com>,
	Lu Baolu <baolu.lu@linux.intel.com>
Subject: Re: [PATCH v2 10/11] vfio: Make vfio_container optionally compiled
Date: Tue, 8 Nov 2022 15:28:31 -0700	[thread overview]
Message-ID: <20221108152831.1a2ed3df.alex.williamson@redhat.com> (raw)
In-Reply-To: <10-v2-65016290f146+33e-vfio_iommufd_jgg@nvidia.com>

On Mon,  7 Nov 2022 20:52:54 -0400
Jason Gunthorpe <jgg@nvidia.com> wrote:

> Add a kconfig CONFIG_VFIO_CONTAINER that controls compiling the container
> code. If 'n' then only iommufd will provide the container service. All the
> support for vfio iommu drivers, including type1, will not be built.
> 
> This allows a compilation check that no inappropriate dependencies between
> the device/group and container have been created.
> 
> Tested-by: Nicolin Chen <nicolinc@nvidia.com>
> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
> ---
>  drivers/vfio/Kconfig  | 35 +++++++++++++++--------
>  drivers/vfio/Makefile |  4 +--
>  drivers/vfio/vfio.h   | 65 +++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 91 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/vfio/Kconfig b/drivers/vfio/Kconfig
> index 1118d322eec97d..286c1663bd7564 100644
> --- a/drivers/vfio/Kconfig
> +++ b/drivers/vfio/Kconfig
> @@ -3,8 +3,8 @@ menuconfig VFIO
>  	tristate "VFIO Non-Privileged userspace driver framework"
>  	select IOMMU_API
>  	depends on IOMMUFD || !IOMMUFD
> -	select VFIO_IOMMU_TYPE1 if MMU && (X86 || S390 || ARM || ARM64)
>  	select INTERVAL_TREE
> +	select VFIO_CONTAINER if IOMMUFD=n
>  	help
>  	  VFIO provides a framework for secure userspace device drivers.
>  	  See Documentation/driver-api/vfio.rst for more details.
> @@ -12,6 +12,18 @@ menuconfig VFIO
>  	  If you don't know what to do here, say N.
>  
>  if VFIO
> +config VFIO_CONTAINER
> +	bool "Support for the VFIO container /dev/vfio/vfio"
> +	select VFIO_IOMMU_TYPE1 if MMU && (X86 || S390 || ARM || ARM64)
> +	default y
> +	help
> +	  The VFIO container is the classic interface to VFIO for establishing
> +	  IOMMU mappings. If N is selected here then IOMMUFD must be used to
> +	  manage the mappings.
> +
> +	  Unless testing IOMMUFD say Y here.
> +
> +if VFIO_CONTAINER
>  config VFIO_IOMMU_TYPE1
>  	tristate
>  	default n
> @@ -21,16 +33,6 @@ config VFIO_IOMMU_SPAPR_TCE
>  	depends on SPAPR_TCE_IOMMU
>  	default VFIO
>  
> -config VFIO_SPAPR_EEH
> -	tristate
> -	depends on EEH && VFIO_IOMMU_SPAPR_TCE
> -	default VFIO
> -
> -config VFIO_VIRQFD
> -	tristate
> -	select EVENTFD
> -	default n
> -
>  config VFIO_NOIOMMU
>  	bool "VFIO No-IOMMU support"
>  	help

Perhaps this should have been obvious, but I'm realizing that
vfio-noiommu mode is completely missing without VFIO_CONTAINER, which
seems a barrier to deprecating VFIO_CONTAINER and perhaps makes it a
question whether IOMMUFD should really be taking over /dev/vfio/vfio.
No-iommu mode has users.  Thanks,

Alex