Re: [PATCH v4 4/7] vfio: ap: register IOMMU VFIO notifier

[Pierre Morel]

On 28/02/2019 09:23, Christian Borntraeger wrote:
> On 22.02.2019 16:29, Pierre Morel wrote:
> > To be able to use the VFIO interface to facilitate the
> > mediated device memory pining/unpining we need to register
> > a notifier for IOMMU.
>
> You might want to add that while we start to pin one guest page for the
> interrupt indicator byte in the next patch, 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.

Thanks, I ll do.

Regards,
Pierre

> > Signed-off-by: Pierre Morel <pmorel@xxxxxxxxxxxxx>
> > ---
> >   drivers/s390/crypto/vfio_ap_ops.c     | 53 ++++++++++++++++++++++++++++++++---
> >   drivers/s390/crypto/vfio_ap_private.h |  2 ++
> >   2 files changed, 51 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
> > index 172d6eb..1b5130a 100644
> > --- a/drivers/s390/crypto/vfio_ap_ops.c
> > +++ b/drivers/s390/crypto/vfio_ap_ops.c
> > @@ -748,6 +748,36 @@ static const struct attribute_group *vfio_ap_mdev_attr_groups[] = {
> >   };
> >   
> >   /**
> > + * vfio_ap_mdev_iommu_notifier: IOMMU notifier callback
> > + *
> > + * @nb: The notifier block
> > + * @action: Action to be taken (VFIO_IOMMU_NOTIFY_DMA_UNMAP)
> > + * @data: the specific unmap structure for vfio_iommu_type1
> > + *
> > + * Unpins the guest IOVA. (The NIB guest address we pinned before).
> > + * Return NOTIFY_OK after unpining on a UNMAP request.
> > + * otherwise, returns NOTIFY_DONE .
> > + */
> > +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;
> > +}
> > +
> > +
> > +/**
> >    * vfio_ap_mdev_set_kvm
> >    *
> >    * @matrix_mdev: a mediated matrix device
> > @@ -846,12 +876,25 @@ static int vfio_ap_mdev_open(struct mdev_device *mdev)
> >   
> >   	ret = vfio_register_notifier(mdev_dev(mdev), VFIO_GROUP_NOTIFY,
> >   				     &events, &matrix_mdev->group_notifier);
> > -	if (ret) {
> > -		module_put(THIS_MODULE);
> > -		return ret;
> > -	}
> > +	if (ret)
> > +		goto err_group;
> > +
> > +	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)
> > +		goto err_iommu;
> >   
> >   	return 0;
> > +
> > +err_iommu:
> > +	vfio_unregister_notifier(mdev_dev(mdev), VFIO_GROUP_NOTIFY,
> > +				 &matrix_mdev->group_notifier);
> > +err_group:
> > +	module_put(THIS_MODULE);
> > +	return ret;
> >   }
> >   
> >   static void vfio_ap_mdev_release(struct mdev_device *mdev)
> > @@ -864,6 +907,8 @@ static void vfio_ap_mdev_release(struct mdev_device *mdev)
> >   	vfio_ap_mdev_reset_queues(mdev);
> >   	vfio_unregister_notifier(mdev_dev(mdev), VFIO_GROUP_NOTIFY,
> >   				 &matrix_mdev->group_notifier);
> > +	vfio_unregister_notifier(mdev_dev(mdev), VFIO_IOMMU_NOTIFY,
> > +				 &matrix_mdev->iommu_notifier);
> >   	matrix_mdev->kvm = NULL;
> >   	module_put(THIS_MODULE);
> >   }
> > diff --git a/drivers/s390/crypto/vfio_ap_private.h b/drivers/s390/crypto/vfio_ap_private.h
> > index 2760178..e535735 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 list_head qlist;
> > +	struct mdev_device *mdev;
> >   };
> >   
> >   extern int vfio_ap_mdev_register(void);


--
Pierre Morel
Linux/KVM/QEMU in BÃblingen - Germany