[PATCH] vhost: do not set VIRTIO_F_IOMMU_PLATFORM when IOMMU is not used

[Jason Wang]

We enable device IOTLB unconditionally when VIRTIO_F_IOMMU_PLATFORM is
negotiated. This lead unnecessary IOTLB miss/update transactions when
IOMMU is used. This patch fixes this.

Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
---
 hw/net/virtio-net.c | 3 +++
 hw/virtio/vhost.c   | 4 +---
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
index 3627bb1717..0d50e8bd34 100644
--- a/hw/net/virtio-net.c
+++ b/hw/net/virtio-net.c
@@ -879,6 +879,9 @@ static void virtio_net_set_features(VirtIODevice *vdev, uint64_t features)
         virtio_net_apply_guest_offloads(n);
     }
 
+    if (vdev->dma_as == &address_space_memory)
+        features &= ~(1ULL << VIRTIO_F_IOMMU_PLATFORM);
+
     for (i = 0;  i < n->max_queues; i++) {
         NetClientState *nc = qemu_get_subqueue(n->nic, i);
 
diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index 9edfadc81d..711b1136f6 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -288,9 +288,7 @@ 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;
-
-    return virtio_host_has_feature(vdev, VIRTIO_F_IOMMU_PLATFORM);
+    return virtio_has_feature(dev->acked_features, VIRTIO_F_IOMMU_PLATFORM);
 }
 
 static void *vhost_memory_map(struct vhost_dev *dev, hwaddr addr,
-- 
2.19.1


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