diff --git a/virtio-devices/src/iommu.rs b/virtio-devices/src/iommu.rs
index 778f46845..8219c3475 100644
--- a/virtio-devices/src/iommu.rs
+++ b/virtio-devices/src/iommu.rs
@@ -73,7 +73,7 @@ const VIRTIO_IOMMU_F_BYPASS_CONFIG: u32 = 6;
 const VIRTIO_IOMMU_PAGE_SIZE_MASK: u64 = (2 << 20) | (4 << 10);
 
 #[derive(Copy, Clone, Debug, Default)]
-#[repr(packed)]
+#[repr(C, packed)]
 #[allow(dead_code)]
 struct VirtioIommuRange32 {
     start: u32,
@@ -81,7 +81,7 @@ struct VirtioIommuRange32 {
 }
 
 #[derive(Copy, Clone, Debug, Default)]
-#[repr(packed)]
+#[repr(C, packed)]
 #[allow(dead_code)]
 struct VirtioIommuRange64 {
     start: u64,
@@ -89,7 +89,7 @@ struct VirtioIommuRange64 {
 }
 
 #[derive(Copy, Clone, Debug, Default)]
-#[repr(packed)]
+#[repr(C, packed)]
 #[allow(dead_code)]
 struct VirtioIommuConfig {
     page_size_mask: u64,
@@ -108,7 +108,7 @@ const VIRTIO_IOMMU_T_UNMAP: u8 = 4;
 const VIRTIO_IOMMU_T_PROBE: u8 = 5;
 
 #[derive(Copy, Clone, Debug, Default)]
-#[repr(packed)]
+#[repr(C, packed)]
 struct VirtioIommuReqHead {
     type_: u8,
     _reserved: [u8; 3],
@@ -134,7 +134,7 @@ const VIRTIO_IOMMU_S_FAULT: u8 = 7;
 const VIRTIO_IOMMU_S_NOMEM: u8 = 8;
 
 #[derive(Copy, Clone, Debug, Default)]
-#[repr(packed)]
+#[repr(C, packed)]
 #[allow(dead_code)]
 struct VirtioIommuReqTail {
     status: u8,
@@ -143,7 +143,7 @@ struct VirtioIommuReqTail {
 
 /// ATTACH request
 #[derive(Copy, Clone, Debug, Default)]
-#[repr(packed)]
+#[repr(C, packed)]
 struct VirtioIommuReqAttach {
     domain: u32,
     endpoint: u32,
@@ -155,7 +155,7 @@ const VIRTIO_IOMMU_ATTACH_F_BYPASS: u32 = 1;
 
 /// DETACH request
 #[derive(Copy, Clone, Debug, Default)]
-#[repr(packed)]
+#[repr(C, packed)]
 struct VirtioIommuReqDetach {
     domain: u32,
     endpoint: u32,
@@ -175,7 +175,7 @@ const VIRTIO_IOMMU_MAP_F_MASK: u32 =
 
 /// MAP request
 #[derive(Copy, Clone, Debug, Default)]
-#[repr(packed)]
+#[repr(C, packed)]
 struct VirtioIommuReqMap {
     domain: u32,
     virt_start: u64,
@@ -186,7 +186,7 @@ struct VirtioIommuReqMap {
 
 /// UNMAP request
 #[derive(Copy, Clone, Debug, Default)]
-#[repr(packed)]
+#[repr(C, packed)]
 struct VirtioIommuReqUnmap {
     domain: u32,
     virt_start: u64,
@@ -203,7 +203,7 @@ const VIRTIO_IOMMU_PROBE_T_MASK: u16 = 0xfff;
 
 /// PROBE request
 #[derive(Copy, Clone, Debug, Default)]
-#[repr(packed)]
+#[repr(C, packed)]
 #[allow(dead_code)]
 struct VirtioIommuReqProbe {
     endpoint: u32,
@@ -211,7 +211,7 @@ struct VirtioIommuReqProbe {
 }
 
 #[derive(Copy, Clone, Debug, Default)]
-#[repr(packed)]
+#[repr(C, packed)]
 #[allow(dead_code)]
 struct VirtioIommuProbeProperty {
     type_: u16,
@@ -224,7 +224,7 @@ const VIRTIO_IOMMU_RESV_MEM_T_RESERVED: u8 = 0;
 const VIRTIO_IOMMU_RESV_MEM_T_MSI: u8 = 1;
 
 #[derive(Copy, Clone, Debug, Default)]
-#[repr(packed)]
+#[repr(C, packed)]
 #[allow(dead_code)]
 struct VirtioIommuProbeResvMem {
     subtype: u8,
@@ -254,7 +254,7 @@ const VIRTIO_IOMMU_FAULT_R_MAPPING: u32 = 2;
 /// Fault reporting through eventq
 #[allow(unused)]
 #[derive(Copy, Clone, Debug, Default)]
-#[repr(packed)]
+#[repr(C, packed)]
 struct VirtioIommuFault {
     reason: u8,
     reserved: [u8; 3],
diff --git a/virtio-devices/src/transport/pci_device.rs b/virtio-devices/src/transport/pci_device.rs
index 6af4afc92..0a12dcc4f 100644
--- a/virtio-devices/src/transport/pci_device.rs
+++ b/virtio-devices/src/transport/pci_device.rs
@@ -60,7 +60,7 @@ enum PciCapabilityType {
 const VIRTIO_PCI_CAP_OFFSET: usize = 2;
 
 #[allow(dead_code)]
-#[repr(packed)]
+#[repr(C, packed)]
 #[derive(Clone, Copy, Default)]
 struct VirtioPciCap {
     cap_len: u8,      // Generic PCI field: capability length
@@ -101,7 +101,7 @@ impl VirtioPciCap {
 }
 
 #[allow(dead_code)]
-#[repr(packed)]
+#[repr(C, packed)]
 #[derive(Clone, Copy, Default)]
 struct VirtioPciNotifyCap {
     cap: VirtioPciCap,
@@ -145,7 +145,7 @@ impl VirtioPciNotifyCap {
 }
 
 #[allow(dead_code)]
-#[repr(packed)]
+#[repr(C, packed)]
 #[derive(Clone, Copy, Default)]
 struct VirtioPciCap64 {
     cap: VirtioPciCap,
@@ -184,7 +184,7 @@ impl VirtioPciCap64 {
 }
 
 #[allow(dead_code)]
-#[repr(packed)]
+#[repr(C, packed)]
 #[derive(Clone, Copy, Default)]
 struct VirtioPciCfgCap {
     cap: VirtioPciCap,