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

Pierre Morel
2019-02-28T08:48:39Z

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@linux.ibm.com>
>> ---
>> 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 Böblingen - Germany