diff --git a/src/arch/aarch64.rs b/src/arch/aarch64.rs
index 9a2de5b48d..8045d60d1b 100644
--- a/src/arch/aarch64.rs
+++ b/src/arch/aarch64.rs
@@ -111,7 +111,7 @@ impl DerefMut for IntRegisters {
 }
 
 #[derive(Clone, Copy, Debug, Default)]
-#[repr(packed)]
+#[repr(C, packed)]
 pub struct FloatRegisters {
     pub fp_simd_regs: [u128; 32],
     pub fpsr: u32,
@@ -142,7 +142,7 @@ impl DerefMut for FloatRegisters {
 }
 
 #[derive(Clone, Copy, Debug, Default)]
-#[repr(packed)]
+#[repr(C, packed)]
 pub struct EnvRegisters {
     pub tpidr_el0: usize,
     pub tpidrro_el0: usize,
diff --git a/src/arch/riscv64.rs b/src/arch/riscv64.rs
index 199f91c9bf..7885d2c3b6 100644
--- a/src/arch/riscv64.rs
+++ b/src/arch/riscv64.rs
@@ -79,7 +79,7 @@ impl DerefMut for IntRegisters {
 }
 
 #[derive(Clone, Copy, Debug, Default)]
-#[repr(packed)]
+#[repr(C, packed)]
 pub struct FloatRegisters {
     //TODO
 }
diff --git a/src/arch/x86.rs b/src/arch/x86.rs
index d43021511d..a1cf93fa8d 100644
--- a/src/arch/x86.rs
+++ b/src/arch/x86.rs
@@ -139,7 +139,7 @@ impl DerefMut for IntRegisters {
 }
 
 #[derive(Clone, Copy, Debug, Default)]
-#[repr(packed)]
+#[repr(C, packed)]
 pub struct FloatRegisters {
     pub fcw: u16,
     pub fsw: u16,
@@ -179,7 +179,7 @@ impl DerefMut for FloatRegisters {
 }
 
 #[derive(Clone, Copy, Debug, Default)]
-#[repr(packed)]
+#[repr(C, packed)]
 pub struct EnvRegisters {
     pub fsbase: u32,
     pub gsbase: u32,
diff --git a/src/arch/x86_64.rs b/src/arch/x86_64.rs
index 6aaca56066..360715c5be 100644
--- a/src/arch/x86_64.rs
+++ b/src/arch/x86_64.rs
@@ -90,7 +90,7 @@ impl DerefMut for IntRegisters {
 }
 
 #[derive(Clone, Copy, Debug, Default)]
-#[repr(packed)]
+#[repr(C, packed)]
 pub struct FloatRegisters {
     pub fcw: u16,
     pub fsw: u16,
@@ -129,7 +129,7 @@ impl DerefMut for FloatRegisters {
     }
 }
 #[derive(Clone, Copy, Debug, Default)]
-#[repr(packed)]
+#[repr(C, packed)]
 pub struct EnvRegisters {
     pub fsbase: u64,
     pub gsbase: u64,
diff --git a/src/io/mmio.rs b/src/io/mmio.rs
index 1af643fa13..1a846f2122 100644
--- a/src/io/mmio.rs
+++ b/src/io/mmio.rs
@@ -4,17 +4,12 @@ use core::{mem::MaybeUninit, ptr};
 
 use super::io::Io;
 
-#[repr(packed)]
+#[repr(transparent)]
 pub struct Mmio<T> {
     value: MaybeUninit<T>,
 }
 
 impl<T> Mmio<T> {
-    /// Create a new Mmio without initializing
-    #[deprecated = "unsound because it's possible to read even though it's uninitialized"]
-    pub fn new() -> Self {
-        unsafe { Self::uninit() }
-    }
     pub unsafe fn zeroed() -> Self {
         Self {
             value: MaybeUninit::zeroed(),