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

Liu, Yi L
2023-07-17T06:36:56Z

> 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.

> 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