vmm: fix dma map when add-device after removing all vfio devices

Now cloud hypervisor do vfio dma map only when first vfio container
created, this can be problematic in some cases. When remove-device
VfioDevice::drop() will be called, which will call VFIO_GROUP_UNSET_CONTAINER
ioctl. The vfio kernel driver detach vfio group and will unpin and
unmap all guest memory when group_list is empty which means the last
vfio device is removed. At this time if a new vfio device is added
cloud hypervisor will not do dma map again and dma access will fail.

Signed-off-by: Yi Wang <foxywang@tencent.com>

Author: up2wing

Cargo.lock

@@ -114,9 +114,9 @@ linux-loader = { git = "https://github.com/rust-vmm/linux-loader", branch = "mai
 mshv-bindings = "0.6.0"
 mshv-ioctls = "0.6.0"
 seccompiler = "0.5.0"
-vfio-bindings = { version = "0.6.0", default-features = false }
-vfio-ioctls = { version = "0.5.1", default-features = false }
-vfio_user = { version = "0.1.1", default-features = false }
+vfio-bindings = { git = "https://github.com/up2wing/vfio.git", branch = "group-ref", default-features = false }
+vfio-ioctls = { git = "https://github.com/up2wing/vfio.git", branch = "group-ref", default-features = false }
+vfio_user = { git = "https://github.com/up2wing/vfio.git", branch = "group-ref", default-features = false }
 vhost = { version = "0.14.0", default-features = false }
 vhost-user-backend = { version = "0.20.0", default-features = false }
 virtio-bindings = "0.2.6"

Cargo.toml

@@ -3742,7 +3742,7 @@ impl DeviceManager {
         let vfio_device = VfioDevice::new(&device_cfg.path, Arc::clone(&vfio_container))
             .map_err(DeviceManagerError::VfioCreate)?;
 
-        if needs_dma_mapping {
+        if needs_dma_mapping || 1 == vfio_container.vfio_group_num() {
             // Register DMA mapping in IOMMU.
             // Do not register virtio-mem regions, as they are handled directly by
             // virtio-mem device itself.