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

Liu, Yi L
2023-07-17T08:09:52Z

> 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?

Regards,
Yi Liu

> > 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