RE: [PATCH v3 14/15] iommufd: vfio container FD ioctl compatibility

From: Jason Gunthorpe jgg@nvidia.com Sent: Wednesday, October 26, 2022 2:12 AM

+int iommufd_vfio_compat_ioas_id(struct iommufd_ctx *ictx, u32 *out_ioas_id) +{

• struct iommufd_ioas *ioas = NULL;
• struct iommufd_ioas *out_ioas;
• ioas = iommufd_ioas_alloc(ictx);
• if (IS_ERR(ioas))

• return PTR_ERR(ioas);
  

I tried to find out where the auto-created compat_ioas is destroyed.

Is my understanding correct that nobody holds a long-term users count on it then we expect it to be destroyed in iommufd release?

If yes, probably worth adding a comment to explain this behavior.

• case IOMMU_VFIO_IOAS_SET:

• ioas = iommufd_get_ioas(ucmd, cmd->ioas_id);
  

• if (IS_ERR(ioas))
  

• 	return PTR_ERR(ioas);
  

• xa_lock(&ucmd->ictx->objects);
  

• ucmd->ictx->vfio_ioas = ioas;
  

• xa_unlock(&ucmd->ictx->objects);
  

• iommufd_put_object(&ioas->obj);
  

• return 0;
  

disallow changing vfio_ioas when it's already in-use e.g. has a list of hwpt attached?