vfio: Add iommufd VFIO compat support to group_fd

IOMMUFD has VFIO compatibility so user space can open /dev/iommu
to reuse existing VFIO IOMMU ioctls. However, the group_fd used
for VFIO_GROUP_SET/UNSET_CONTAINER is still a VFIO thing and is
not supported using new IOMMUFD ioctls, which go for an approach
of attaching and dettaching a VFIO device directly instead of a
VFIO group.

In order to fill this gap, IOMMUFD provides a pair of helpers to
VFIO to call, so as to bind/unbind all devices in the VFIO group
to/from the iommufd and to attach/detach them to/from the ioas.

So this patch simply calls those two helpers in cases where user
space uses VFIO ioctls on top of /dev/iommu and wants to connect
group_fd to that.

Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Yi Liu <yi.l.liu@intel.com>

drivers/iommu/iommufd/vfio_compat.c

@@ -153,7 +153,7 @@ static int iommufd_vfio_unmap_dma(struct iommufd_ctx *ictx, unsigned int cmd,
 	return rc;
 }
 
-static int iommufd_vfio_check_extension(unsigned long type)
+int iommufd_vfio_check_extension(unsigned long type)
 {
 	switch (type) {
 	case VFIO_TYPE1v2_IOMMU:
@@ -205,6 +205,7 @@ static int iommufd_vfio_check_extension(unsigned long type)
   * review along side HW drivers implementing it.
   */
 }
+EXPORT_SYMBOL_GPL(iommufd_vfio_check_extension);
 
 static int iommufd_vfio_set_iommu(struct iommufd_ctx *ictx, unsigned long type)
 {

drivers/vfio/Kconfig

@@ -2,6 +2,7 @@
 menuconfig VFIO
 	tristate "VFIO Non-Privileged userspace driver framework"
 	select IOMMU_API
+	select IOMMUFD if MMU && (X86 || S390 || ARM || ARM64)
 	select VFIO_IOMMU_TYPE1 if MMU && (X86 || S390 || ARM || ARM64)
 	help
 	  VFIO provides a framework for secure userspace device drivers.

drivers/vfio/vfio.c

@@ -84,6 +84,7 @@ struct vfio_group {
 	unsigned int			dev_counter;
 	struct kvm			*kvm;
 	struct blocking_notifier_head	notifier;
+	void				*iommufd;
 };
 
 #ifdef CONFIG_VFIO_NOIOMMU
@@ -1079,6 +1080,12 @@ static void __vfio_group_unset_container(struct vfio_group *group)
 	struct vfio_container *container = group->container;
 	struct vfio_iommu_driver *driver;
 
+	if (group->iommufd) {
+		vfio_group_unset_iommufd(group->iommufd, &group->device_list);
+		group->iommufd = NULL;
+		return;
+	}
+
 	down_write(&container->group_lock);
 
 	driver = container->iommu_driver;
@@ -1150,6 +1157,13 @@ static int vfio_group_set_container(struct vfio_group *group, int container_fd)
 	if (group->type == VFIO_NO_IOMMU && !capable(CAP_SYS_RAWIO))
 		return -EPERM;
 
+	group->iommufd = vfio_group_set_iommufd(container_fd,
+						&group->device_list);
+	if (group->iommufd) {
+		atomic_inc(&group->container_users);
+		return ret;
+	}
+
 	f = fdget(container_fd);
 	if (!f.file)
 		return -EBADF;
@@ -1210,7 +1224,7 @@ static int vfio_group_add_container_user(struct vfio_group *group)
 		atomic_dec(&group->container_users);
 		return -EPERM;
 	}
-	if (!group->container->iommu_driver) {
+	if ((group->container && !group->container->iommu_driver) || !group->iommufd) {
 		atomic_dec(&group->container_users);
 		return -EINVAL;
 	}
@@ -1261,7 +1275,8 @@ static int vfio_group_get_device_fd(struct vfio_group *group, char *buf)
 	int ret = 0;
 
 	if (0 == atomic_read(&group->container_users) ||
-	    !group->container->iommu_driver)
+	    (group->container && !group->container->iommu_driver) ||
+	    (!group->container && !group->iommufd))
 		return -EINVAL;
 
 	if (group->type == VFIO_NO_IOMMU && !capable(CAP_SYS_RAWIO))
@@ -1775,6 +1790,9 @@ EXPORT_SYMBOL_GPL(vfio_external_user_iommu_id);
 
 long vfio_external_check_extension(struct vfio_group *group, unsigned long arg)
 {
+	if (group->iommufd)
+		return iommufd_vfio_check_extension(arg);
+
 	return vfio_ioctl_check_extension(group->container, arg);
 }
 EXPORT_SYMBOL_GPL(vfio_external_check_extension);

include/linux/iommufd.h

@@ -31,6 +31,7 @@ void iommufd_device_detach(struct iommufd_device *idev);
 
 struct iommufd_ctx *vfio_group_set_iommufd(int fd, struct list_head *device_list);
 void vfio_group_unset_iommufd(void *iommufd, struct list_head *device_list);
+int iommufd_vfio_check_extension(unsigned long type);
 #else /* !CONFIG_IOMMUFD */
 static inline struct iommufd_device *
 iommufd_bind_pci_device(int fd, struct pci_dev *pdev, u32 *id)
@@ -62,5 +63,10 @@ static inline void vfio_group_unset_iommufd(void *iommufd,
 					    struct list_head *device_list)
 {
 }
+
+static int iommufd_vfio_check_extension(unsigned long type)
+{
+	return -EOPNOTSUPP;
+}
 #endif /* CONFIG_IOMMUFD */
 #endif