Re: [Qemu-devel] [PATCH for 2.9] vhost: generalize iommu memory region

[Peter Xu <peterx@redhat.com>]

On Wed, Mar 29, 2017 at 12:10:04PM +0800, Jason Wang wrote:
> We assumes the iommu_ops were attached to the root region of address
> space. This may not be true for all kinds of IOMMU implementation and
> especially after commit 3716d5902d74 ("pci: introduce a bus master
> container"). So fix this by not assuming as->root has iommu_ops,
> instead depending on the regions reported by memory listener through:
> 
> - register a memory listener to dma_as
> - during region_add, if it's a region of IOMMU, register a specific
>   IOMMU notifier, and store all notifiers in a list.
> - during region_del, compare and delete the IOMMU notifier from the list
> 
> This is also a must for making vhost device IOTLB works for all types
> of IOMMUs. Note, since we register one notifier during each
> .region_add, the IOTLB may be flushed more than one times, this is
> suboptimal and could be optimized in the future.

I guess I'll need to tune vtd-vfio series as well for this - now vhost
would have the same dup-flush issue just like vfio, and in that series
we need to settle both.

I'm thinking maybe I should post a new version for that series as well
even before 2.9 release for some early review comments.

> 
> Reported-by: Maxime Coquelin <maxime.coquelin@redhat.com>
> Fixes: 3716d5902d74 ("pci: introduce a bus master container")
> Cc: Peter Xu <peterx@redhat.com>
> Signed-off-by: Jason Wang <jasowang@redhat.com>

Reviewed-by: Peter Xu <peterx@redhat.com>

If this patch will make it for 2.9, I'll drop the corresponding one in
my series, but only keep the other one ("intel_iommu: use the correct
memory region for device IOTLB notification"). Thanks,

> ---
>  hw/virtio/vhost.c         | 84 ++++++++++++++++++++++++++++++++++++-----------
>  include/hw/virtio/vhost.h | 11 +++++++
>  2 files changed, 75 insertions(+), 20 deletions(-)
> 
> diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> index febe519..613494d 100644
> --- a/hw/virtio/vhost.c
> +++ b/hw/virtio/vhost.c
> @@ -425,10 +425,8 @@ static inline void vhost_dev_log_resize(struct vhost_dev *dev, uint64_t size)
>  static int vhost_dev_has_iommu(struct vhost_dev *dev)
>  {
>      VirtIODevice *vdev = dev->vdev;
> -    AddressSpace *dma_as = vdev->dma_as;
>  
> -    return memory_region_is_iommu(dma_as->root) &&
> -           virtio_host_has_feature(vdev, VIRTIO_F_IOMMU_PLATFORM);
> +    return virtio_host_has_feature(vdev, VIRTIO_F_IOMMU_PLATFORM);
>  }
>  
>  static void *vhost_memory_map(struct vhost_dev *dev, hwaddr addr,
> @@ -720,6 +718,63 @@ static void vhost_region_del(MemoryListener *listener,
>      }
>  }
>  
> +static void vhost_iommu_unmap_notify(IOMMUNotifier *n, IOMMUTLBEntry *iotlb)
> +{
> +    struct vhost_iommu *iommu = container_of(n, struct vhost_iommu, n);
> +    struct vhost_dev *hdev = iommu->hdev;
> +    hwaddr iova = iotlb->iova + iommu->iommu_offset;
> +
> +    if (hdev->vhost_ops->vhost_invalidate_device_iotlb(hdev, iova,
> +                                                       iotlb->addr_mask + 1)) {
> +        error_report("Fail to invalidate device iotlb");
> +    }
> +}
> +
> +static void vhost_iommu_region_add(MemoryListener *listener,
> +                                   MemoryRegionSection *section)
> +{
> +    struct vhost_dev *dev = container_of(listener, struct vhost_dev,
> +                                         iommu_listener);
> +    struct vhost_iommu *iommu;
> +
> +    if (!memory_region_is_iommu(section->mr)) {
> +        return;
> +    }
> +
> +    iommu = g_malloc0(sizeof(*iommu));
> +    iommu->n.notify = vhost_iommu_unmap_notify;
> +    iommu->n.notifier_flags = IOMMU_NOTIFIER_UNMAP;
> +    iommu->mr = section->mr;
> +    iommu->iommu_offset = section->offset_within_address_space -
> +                          section->offset_within_region;
> +    iommu->hdev = dev;
> +    memory_region_register_iommu_notifier(section->mr, &iommu->n);
> +    QLIST_INSERT_HEAD(&dev->iommu_list, iommu, iommu_next);
> +    /* TODO: can replay help performance here? */
> +}
> +
> +static void vhost_iommu_region_del(MemoryListener *listener,
> +                                   MemoryRegionSection *section)
> +{
> +    struct vhost_dev *dev = container_of(listener, struct vhost_dev,
> +                                         iommu_listener);
> +    struct vhost_iommu *iommu;
> +
> +    if (!memory_region_is_iommu(section->mr)) {
> +        return;
> +    }
> +
> +    QLIST_FOREACH(iommu, &dev->iommu_list, iommu_next) {
> +        if (iommu->mr == section->mr) {
> +            memory_region_unregister_iommu_notifier(iommu->mr,
> +                                                    &iommu->n);
> +            QLIST_REMOVE(iommu, iommu_next);
> +            g_free(iommu);
> +            break;
> +        }
> +    }
> +}
> +
>  static void vhost_region_nop(MemoryListener *listener,
>                               MemoryRegionSection *section)
>  {
> @@ -1161,17 +1216,6 @@ static void vhost_virtqueue_cleanup(struct vhost_virtqueue *vq)
>      event_notifier_cleanup(&vq->masked_notifier);
>  }
>  
> -static void vhost_iommu_unmap_notify(IOMMUNotifier *n, IOMMUTLBEntry *iotlb)
> -{
> -    struct vhost_dev *hdev = container_of(n, struct vhost_dev, n);
> -
> -    if (hdev->vhost_ops->vhost_invalidate_device_iotlb(hdev,
> -                                                       iotlb->iova,
> -                                                       iotlb->addr_mask + 1)) {
> -        error_report("Fail to invalidate device iotlb");
> -    }
> -}
> -
>  int vhost_dev_init(struct vhost_dev *hdev, void *opaque,
>                     VhostBackendType backend_type, uint32_t busyloop_timeout)
>  {
> @@ -1244,8 +1288,10 @@ int vhost_dev_init(struct vhost_dev *hdev, void *opaque,
>          .priority = 10
>      };
>  
> -    hdev->n.notify = vhost_iommu_unmap_notify;
> -    hdev->n.notifier_flags = IOMMU_NOTIFIER_UNMAP;
> +    hdev->iommu_listener = (MemoryListener) {
> +        .region_add = vhost_iommu_region_add,
> +        .region_del = vhost_iommu_region_del,
> +    };
>  
>      if (hdev->migration_blocker == NULL) {
>          if (!(hdev->features & (0x1ULL << VHOST_F_LOG_ALL))) {
> @@ -1455,8 +1501,7 @@ int vhost_dev_start(struct vhost_dev *hdev, VirtIODevice *vdev)
>      }
>  
>      if (vhost_dev_has_iommu(hdev)) {
> -        memory_region_register_iommu_notifier(vdev->dma_as->root,
> -                                              &hdev->n);
> +        memory_listener_register(&hdev->iommu_listener, vdev->dma_as);
>      }
>  
>      r = hdev->vhost_ops->vhost_set_mem_table(hdev, hdev->mem);
> @@ -1538,8 +1583,7 @@ void vhost_dev_stop(struct vhost_dev *hdev, VirtIODevice *vdev)
>  
>      if (vhost_dev_has_iommu(hdev)) {
>          hdev->vhost_ops->vhost_set_iotlb_callback(hdev, false);
> -        memory_region_unregister_iommu_notifier(vdev->dma_as->root,
> -                                                &hdev->n);
> +        memory_listener_unregister(&hdev->iommu_listener);
>      }
>      vhost_log_put(hdev, true);
>      hdev->started = false;
> diff --git a/include/hw/virtio/vhost.h b/include/hw/virtio/vhost.h
> index 52f633e..a450321 100644
> --- a/include/hw/virtio/vhost.h
> +++ b/include/hw/virtio/vhost.h
> @@ -37,10 +37,20 @@ struct vhost_log {
>      vhost_log_chunk_t *log;
>  };
>  
> +struct vhost_dev;
> +struct vhost_iommu {
> +    struct vhost_dev *hdev;
> +    MemoryRegion *mr;
> +    hwaddr iommu_offset;
> +    IOMMUNotifier n;
> +    QLIST_ENTRY(vhost_iommu) iommu_next;
> +};
> +
>  struct vhost_memory;
>  struct vhost_dev {
>      VirtIODevice *vdev;
>      MemoryListener memory_listener;
> +    MemoryListener iommu_listener;
>      struct vhost_memory *mem;
>      int n_mem_sections;
>      MemoryRegionSection *mem_sections;
> @@ -64,6 +74,7 @@ struct vhost_dev {
>      void *opaque;
>      struct vhost_log *log;
>      QLIST_ENTRY(vhost_dev) entry;
> +    QLIST_HEAD(, vhost_iommu) iommu_list;
>      IOMMUNotifier n;
>  };
>  
> -- 
> 2.7.4
> 

-- peterx