Re: [PATCH v13 21/22] vfio: Compile vfio_group infrastructure optionally

[Alex Williamson <alex.williamson@redhat.com>]

On Mon, 17 Jul 2023 08:08:59 +0000
"Liu, Yi L" <yi.l.liu@intel.com> wrote:

> > From: Liu, Yi L <yi.l.liu@intel.com>
> > Sent: Monday, July 17, 2023 2:36 PM
> >   
> > > From: Liu, Yi L <yi.l.liu@intel.com>
> > > Sent: Friday, June 16, 2023 5:40 PM
> > >
> > > vfio_group is not needed for vfio device cdev, so with vfio device cdev
> > > introduced, the vfio_group infrastructures can be compiled out if only
> > > cdev is needed.
> > >
> > > Tested-by: Nicolin Chen <nicolinc@nvidia.com>
> > > Tested-by: Matthew Rosato <mjrosato@linux.ibm.com>
> > > Tested-by: Yanting Jiang <yanting.jiang@intel.com>
> > > Tested-by: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>
> > > Tested-by: Terrence Xu <terrence.xu@intel.com>
> > > Signed-off-by: Yi Liu <yi.l.liu@intel.com>
> > > ---
> > >  drivers/iommu/iommufd/Kconfig |  4 +-
> > >  drivers/vfio/Kconfig          | 15 ++++++
> > >  drivers/vfio/Makefile         |  2 +-
> > >  drivers/vfio/vfio.h           | 89 ++++++++++++++++++++++++++++++++---
> > >  include/linux/vfio.h          | 25 ++++++++--
> > >  5 files changed, 123 insertions(+), 12 deletions(-)
> > >
> > > diff --git a/drivers/iommu/iommufd/Kconfig b/drivers/iommu/iommufd/Kconfig
> > > index ada693ea51a7..99d4b075df49 100644
> > > --- a/drivers/iommu/iommufd/Kconfig
> > > +++ b/drivers/iommu/iommufd/Kconfig
> > > @@ -14,8 +14,8 @@ config IOMMUFD
> > >  if IOMMUFD
> > >  config IOMMUFD_VFIO_CONTAINER
> > >  	bool "IOMMUFD provides the VFIO container /dev/vfio/vfio"
> > > -	depends on VFIO && !VFIO_CONTAINER
> > > -	default VFIO && !VFIO_CONTAINER
> > > +	depends on VFIO_GROUP && !VFIO_CONTAINER
> > > +	default VFIO_GROUP && !VFIO_CONTAINER  
> > 
> > Hi Alex, Jason,
> > 
> > I found a minor nit on the kconfig. The below configuration is valid.
> > But user cannot use vfio directly as there is no /dev/vfio/vfio. Although
> > user can open /dev/iommu instead. This is not good.
> > 
> > CONFIG_IOMMUFD=y
> > CONFIG_VFIO_DEVICE_CDEv=n
> > CONFIG_VFIO_GROUP=y
> > CONFIG_VFIO_CONTAINER=n
> > CONFIG_IOMMUFD_VFIO_CONTAINER=n
> > 
> > So need to have the below change. I'll incorporate this change in
> > this series after your ack.
> > 
> > diff --git a/drivers/iommu/iommufd/Kconfig b/drivers/iommu/iommufd/Kconfig
> > index 99d4b075df49..d675c96c2bbb 100644
> > --- a/drivers/iommu/iommufd/Kconfig
> > +++ b/drivers/iommu/iommufd/Kconfig
> > @@ -14,8 +14,8 @@ config IOMMUFD
> >  if IOMMUFD
> >  config IOMMUFD_VFIO_CONTAINER
> >  	bool "IOMMUFD provides the VFIO container /dev/vfio/vfio"
> > -	depends on VFIO_GROUP && !VFIO_CONTAINER
> > -	default VFIO_GROUP && !VFIO_CONTAINER
> > +	depends on VFIO_GROUP
> > +	default n
> >  	help
> >  	  IOMMUFD will provide /dev/vfio/vfio instead of VFIO. This relies on
> >  	  IOMMUFD providing compatibility emulation to give the same ioctls.
> > diff --git a/drivers/vfio/Kconfig b/drivers/vfio/Kconfig
> > index 6bda6dbb4878..ee3bbad6beb8 100644
> > --- a/drivers/vfio/Kconfig
> > +++ b/drivers/vfio/Kconfig
> > @@ -6,7 +6,7 @@ menuconfig VFIO
> >  	select INTERVAL_TREE
> >  	select VFIO_GROUP if SPAPR_TCE_IOMMU || IOMMUFD=n
> >  	select VFIO_DEVICE_CDEV if !VFIO_GROUP
> > -	select VFIO_CONTAINER if IOMMUFD=n
> > +	select VFIO_CONTAINER if IOMMUFD_VFIO_CONTAINER=n
> >  	help
> >  	  VFIO provides a framework for secure userspace device drivers.
> >  	  See Documentation/driver-api/vfio.rst for more details.
> >   
> 
> Just realized that it is possible to config both VFIO_CONTAINER and
> IOMMUFD_VFIO_CONTAINER to "y". Then there will be a conflict when
> registering /dev/vfio/vfio. Any suggestion?

This is only an issue with the proposed change, right?  I agree with
Jason, removing /dev/vfio/vfio entirely should be possible.  That's
actually our ultimate goal, but obviously it breaks current userspace
depending on vfio container compatibility.  It's a configuration error,
not a Kconfig error if someone finds themselves without /dev/vfio/vfio
currently.  Thanks,

Alex

> > >  	help
> > >  	  IOMMUFD will provide /dev/vfio/vfio instead of VFIO. This relies on
> > >  	  IOMMUFD providing compatibility emulation to give the same ioctls.
> > > diff --git a/drivers/vfio/Kconfig b/drivers/vfio/Kconfig
> > > index 1cab8e4729de..35ab8ab87688 100644
> > > --- a/drivers/vfio/Kconfig
> > > +++ b/drivers/vfio/Kconfig
> > > @@ -4,6 +4,8 @@ menuconfig VFIO
> > >  	select IOMMU_API
> > >  	depends on IOMMUFD || !IOMMUFD
> > >  	select INTERVAL_TREE
> > > +	select VFIO_GROUP if SPAPR_TCE_IOMMU || IOMMUFD=n
> > > +	select VFIO_DEVICE_CDEV if !VFIO_GROUP
> > >  	select VFIO_CONTAINER if IOMMUFD=n  
> > 
> > This should be " select VFIO_CONTAINER if IOMMUFD_VFIO_CONTAINER=n"
> > 
> > Regards,
> > Yi Liu
> >   
> > >  	help
> > >  	  VFIO provides a framework for secure userspace device drivers.
> > > @@ -15,6 +17,7 @@ if VFIO
> > >  config VFIO_DEVICE_CDEV
> > >  	bool "Support for the VFIO cdev /dev/vfio/devices/vfioX"
> > >  	depends on IOMMUFD
> > > +	default !VFIO_GROUP
> > >  	help
> > >  	  The VFIO device cdev is another way for userspace to get device
> > >  	  access. Userspace gets device fd by opening device cdev under
> > > @@ -24,9 +27,20 @@ config VFIO_DEVICE_CDEV
> > >
> > >  	  If you don't know what to do here, say N.
> > >
> > > +config VFIO_GROUP
> > > +	bool "Support for the VFIO group /dev/vfio/$group_id"
> > > +	default y
> > > +	help
> > > +	   VFIO group support provides the traditional model for accessing
> > > +	   devices through VFIO and is used by the majority of userspace
> > > +	   applications and drivers making use of VFIO.
> > > +
> > > +	   If you don't know what to do here, say Y.
> > > +
> > >  config VFIO_CONTAINER
> > >  	bool "Support for the VFIO container /dev/vfio/vfio"
> > >  	select VFIO_IOMMU_TYPE1 if MMU && (X86 || S390 || ARM || ARM64)
> > > +	depends on VFIO_GROUP
> > >  	default y
> > >  	help
> > >  	  The VFIO container is the classic interface to VFIO for establishing
> > > @@ -48,6 +62,7 @@ endif
> > >
> > >  config VFIO_NOIOMMU
> > >  	bool "VFIO No-IOMMU support"
> > > +	depends on VFIO_GROUP
> > >  	help
> > >  	  VFIO is built on the ability to isolate devices using the IOMMU.
> > >  	  Only with an IOMMU can userspace access to DMA capable devices be
> > > diff --git a/drivers/vfio/Makefile b/drivers/vfio/Makefile
> > > index 245394aeb94b..57c3515af606 100644
> > > --- a/drivers/vfio/Makefile
> > > +++ b/drivers/vfio/Makefile
> > > @@ -2,9 +2,9 @@
> > >  obj-$(CONFIG_VFIO) += vfio.o
> > >
> > >  vfio-y += vfio_main.o \
> > > -	  group.o \
> > >  	  iova_bitmap.o
> > >  vfio-$(CONFIG_VFIO_DEVICE_CDEV) += device_cdev.o
> > > +vfio-$(CONFIG_VFIO_GROUP) += group.o
> > >  vfio-$(CONFIG_IOMMUFD) += iommufd.o
> > >  vfio-$(CONFIG_VFIO_CONTAINER) += container.o
> > >  vfio-$(CONFIG_VFIO_VIRQFD) += virqfd.o
> > > diff --git a/drivers/vfio/vfio.h b/drivers/vfio/vfio.h
> > > index e7a3fe093362..b27a3915e6c9 100644
> > > --- a/drivers/vfio/vfio.h
> > > +++ b/drivers/vfio/vfio.h
> > > @@ -36,6 +36,12 @@ vfio_allocate_device_file(struct vfio_device *device);
> > >
> > >  extern const struct file_operations vfio_device_fops;
> > >
> > > +#ifdef CONFIG_VFIO_NOIOMMU
> > > +extern bool vfio_noiommu __read_mostly;
> > > +#else
> > > +enum { vfio_noiommu = false };
> > > +#endif
> > > +
> > >  enum vfio_group_type {
> > >  	/*
> > >  	 * Physical device with IOMMU backing.
> > > @@ -60,6 +66,7 @@ enum vfio_group_type {
> > >  	VFIO_NO_IOMMU,
> > >  };
> > >
> > > +#if IS_ENABLED(CONFIG_VFIO_GROUP)
> > >  struct vfio_group {
> > >  	struct device 			dev;
> > >  	struct cdev			cdev;
> > > @@ -111,6 +118,82 @@ static inline bool vfio_device_is_noiommu(struct vfio_device
> > > *vdev)
> > >  	return IS_ENABLED(CONFIG_VFIO_NOIOMMU) &&
> > >  	       vdev->group->type == VFIO_NO_IOMMU;
> > >  }
> > > +#else
> > > +struct vfio_group;
> > > +
> > > +static inline int vfio_device_block_group(struct vfio_device *device)
> > > +{
> > > +	return 0;
> > > +}
> > > +
> > > +static inline void vfio_device_unblock_group(struct vfio_device *device)
> > > +{
> > > +}
> > > +
> > > +static inline int vfio_device_set_group(struct vfio_device *device,
> > > +					enum vfio_group_type type)
> > > +{
> > > +	return 0;
> > > +}
> > > +
> > > +static inline void vfio_device_remove_group(struct vfio_device *device)
> > > +{
> > > +}
> > > +
> > > +static inline void vfio_device_group_register(struct vfio_device *device)
> > > +{
> > > +}
> > > +
> > > +static inline void vfio_device_group_unregister(struct vfio_device *device)
> > > +{
> > > +}
> > > +
> > > +static inline int vfio_device_group_use_iommu(struct vfio_device *device)
> > > +{
> > > +	return -EOPNOTSUPP;
> > > +}
> > > +
> > > +static inline void vfio_device_group_unuse_iommu(struct vfio_device *device)
> > > +{
> > > +}
> > > +
> > > +static inline void vfio_df_group_close(struct vfio_device_file *df)
> > > +{
> > > +}
> > > +
> > > +static inline struct vfio_group *vfio_group_from_file(struct file *file)
> > > +{
> > > +	return NULL;
> > > +}
> > > +
> > > +static inline bool vfio_group_enforced_coherent(struct vfio_group *group)
> > > +{
> > > +	return true;
> > > +}
> > > +
> > > +static inline void vfio_group_set_kvm(struct vfio_group *group, struct kvm *kvm)
> > > +{
> > > +}
> > > +
> > > +static inline bool vfio_device_has_container(struct vfio_device *device)
> > > +{
> > > +	return false;
> > > +}
> > > +
> > > +static inline int __init vfio_group_init(void)
> > > +{
> > > +	return 0;
> > > +}
> > > +
> > > +static inline void vfio_group_cleanup(void)
> > > +{
> > > +}
> > > +
> > > +static inline bool vfio_device_is_noiommu(struct vfio_device *vdev)
> > > +{
> > > +	return false;
> > > +}
> > > +#endif /* CONFIG_VFIO_GROUP */
> > >
> > >  #if IS_ENABLED(CONFIG_VFIO_CONTAINER)
> > >  /**
> > > @@ -362,12 +445,6 @@ static inline void vfio_virqfd_exit(void)
> > >  }
> > >  #endif
> > >
> > > -#ifdef CONFIG_VFIO_NOIOMMU
> > > -extern bool vfio_noiommu __read_mostly;
> > > -#else
> > > -enum { vfio_noiommu = false };
> > > -#endif
> > > -
> > >  #ifdef CONFIG_HAVE_KVM
> > >  void _vfio_device_get_kvm_safe(struct vfio_device *device, struct kvm *kvm);
> > >  void vfio_device_put_kvm(struct vfio_device *device);
> > > diff --git a/include/linux/vfio.h b/include/linux/vfio.h
> > > index d6228c839c44..5a1dee983f17 100644
> > > --- a/include/linux/vfio.h
> > > +++ b/include/linux/vfio.h
> > > @@ -43,7 +43,11 @@ struct vfio_device {
> > >  	 */
> > >  	const struct vfio_migration_ops *mig_ops;
> > >  	const struct vfio_log_ops *log_ops;
> > > +#if IS_ENABLED(CONFIG_VFIO_GROUP)
> > >  	struct vfio_group *group;
> > > +	struct list_head group_next;
> > > +	struct list_head iommu_entry;
> > > +#endif
> > >  	struct vfio_device_set *dev_set;
> > >  	struct list_head dev_set_list;
> > >  	unsigned int migration_flags;
> > > @@ -58,8 +62,6 @@ struct vfio_device {
> > >  	refcount_t refcount;	/* user count on registered device*/
> > >  	unsigned int open_count;
> > >  	struct completion comp;
> > > -	struct list_head group_next;
> > > -	struct list_head iommu_entry;
> > >  	struct iommufd_access *iommufd_access;
> > >  	void (*put_kvm)(struct kvm *kvm);
> > >  #if IS_ENABLED(CONFIG_IOMMUFD)
> > > @@ -284,12 +286,29 @@ int vfio_mig_get_next_state(struct vfio_device *device,
> > >  /*
> > >   * External user API
> > >   */
> > > +#if IS_ENABLED(CONFIG_VFIO_GROUP)
> > >  struct iommu_group *vfio_file_iommu_group(struct file *file);
> > >  bool vfio_file_is_group(struct file *file);
> > > +bool vfio_file_has_dev(struct file *file, struct vfio_device *device);
> > > +#else
> > > +static inline struct iommu_group *vfio_file_iommu_group(struct file *file)
> > > +{
> > > +	return NULL;
> > > +}
> > > +
> > > +static inline bool vfio_file_is_group(struct file *file)
> > > +{
> > > +	return false;
> > > +}
> > > +
> > > +static inline bool vfio_file_has_dev(struct file *file, struct vfio_device *device)
> > > +{
> > > +	return false;
> > > +}
> > > +#endif
> > >  bool vfio_file_is_valid(struct file *file);
> > >  bool vfio_file_enforced_coherent(struct file *file);
> > >  void vfio_file_set_kvm(struct file *file, struct kvm *kvm);
> > > -bool vfio_file_has_dev(struct file *file, struct vfio_device *device);
> > >
> > >  #define VFIO_PIN_PAGES_MAX_ENTRIES	(PAGE_SIZE/sizeof(unsigned long))
> > >
> > > --
> > > 2.34.1  
>