Re: [PATCH v9 2/4] vfio: ap: register IOMMU VFIO notifier

[Harald Freudenberger <freude@linux.ibm.com>]

On 21.05.19 17:34, Pierre Morel wrote:
> To be able to use the VFIO interface to facilitate the
> mediated device memory pinning/unpinning we need to register
> a notifier for IOMMU.
>
> While we will start to pin one guest page for the interrupt indicator
> byte, this is still ok with ballooning as this page will never be
> used by the guest virtio-balloon driver.
> So the pinned page will never be freed. And even a broken guest does
> so, that would not impact the host as the original page is still
> in control by vfio.
>
> Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
> Reviewed-by: Cornelia Huck <cohuck@redhat.com>
> Reviewed-by: Tony Krowiak <akrowiak@linux.ibm.com>
> ---
>  drivers/s390/crypto/vfio_ap_ops.c     | 43 ++++++++++++++++++++++++++++++++++-
>  drivers/s390/crypto/vfio_ap_private.h |  2 ++
>  2 files changed, 44 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
> index 900b9cf..e8e87bf 100644
> --- a/drivers/s390/crypto/vfio_ap_ops.c
> +++ b/drivers/s390/crypto/vfio_ap_ops.c
> @@ -759,6 +759,35 @@ static int vfio_ap_mdev_set_kvm(struct ap_matrix_mdev *matrix_mdev,
>  	return 0;
>  }
>  
> +/*
> + * vfio_ap_mdev_iommu_notifier: IOMMU notifier callback
> + *
> + * @nb: The notifier block
> + * @action: Action to be taken
> + * @data: data associated with the request
> + *
> + * For an UNMAP request, unpin the guest IOVA (the NIB guest address we
> + * pinned before). Other requests are ignored.
> + *
> + */
> +static int vfio_ap_mdev_iommu_notifier(struct notifier_block *nb,
> +				       unsigned long action, void *data)
> +{
> +	struct ap_matrix_mdev *matrix_mdev;
> +
> +	matrix_mdev = container_of(nb, struct ap_matrix_mdev, iommu_notifier);
> +
> +	if (action == VFIO_IOMMU_NOTIFY_DMA_UNMAP) {
> +		struct vfio_iommu_type1_dma_unmap *unmap = data;
> +		unsigned long g_pfn = unmap->iova >> PAGE_SHIFT;
> +
> +		vfio_unpin_pages(mdev_dev(matrix_mdev->mdev), &g_pfn, 1);
> +		return NOTIFY_OK;
> +	}
> +
> +	return NOTIFY_DONE;
> +}
> +
>  static int vfio_ap_mdev_group_notifier(struct notifier_block *nb,
>  				       unsigned long action, void *data)
>  {
> @@ -858,7 +887,17 @@ static int vfio_ap_mdev_open(struct mdev_device *mdev)
>  		return ret;
>  	}
>  
> -	return 0;
> +	matrix_mdev->iommu_notifier.notifier_call = vfio_ap_mdev_iommu_notifier;
> +	events = VFIO_IOMMU_NOTIFY_DMA_UNMAP;
> +	ret = vfio_register_notifier(mdev_dev(mdev), VFIO_IOMMU_NOTIFY,
> +				     &events, &matrix_mdev->iommu_notifier);
> +	if (!ret)
> +		return ret;
> +
> +	vfio_unregister_notifier(mdev_dev(mdev), VFIO_GROUP_NOTIFY,
> +				 &matrix_mdev->group_notifier);
> +	module_put(THIS_MODULE);
> +	return ret;
>  }
>  
>  static void vfio_ap_mdev_release(struct mdev_device *mdev)
> @@ -869,6 +908,8 @@ static void vfio_ap_mdev_release(struct mdev_device *mdev)
>  		kvm_arch_crypto_clear_masks(matrix_mdev->kvm);
>  
>  	vfio_ap_mdev_reset_queues(mdev);
> +	vfio_unregister_notifier(mdev_dev(mdev), VFIO_IOMMU_NOTIFY,
> +				 &matrix_mdev->iommu_notifier);
>  	vfio_unregister_notifier(mdev_dev(mdev), VFIO_GROUP_NOTIFY,
>  				 &matrix_mdev->group_notifier);
>  	matrix_mdev->kvm = NULL;
> diff --git a/drivers/s390/crypto/vfio_ap_private.h b/drivers/s390/crypto/vfio_ap_private.h
> index a910be1..18dcc4d 100644
> --- a/drivers/s390/crypto/vfio_ap_private.h
> +++ b/drivers/s390/crypto/vfio_ap_private.h
> @@ -81,8 +81,10 @@ struct ap_matrix_mdev {
>  	struct list_head node;
>  	struct ap_matrix matrix;
>  	struct notifier_block group_notifier;
> +	struct notifier_block iommu_notifier;
>  	struct kvm *kvm;
>  	struct kvm_s390_module_hook pqap_hook;
> +	struct mdev_device *mdev;
>  };
>  
>  extern int vfio_ap_mdev_register(void);
acked-by: Harald Freudenberger <freude@linux.ibm.com>