From f4751c7a42b194eb4166c7f3f294bf89c3e23cd9 Mon Sep 17 00:00:00 2001
From: Paolo Bonzini <pbonzini@redhat.com>
Date: Fri, 14 Feb 2025 11:45:36 +0100
Subject: [PATCH] rust: sysbus: wrap SysBusDevice with Opaque<>

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 rust/qemu-api/src/bindings.rs |  3 ---
 rust/qemu-api/src/sysbus.rs   | 29 +++++++++++++++++++++--------
 2 files changed, 21 insertions(+), 11 deletions(-)

diff --git a/rust/qemu-api/src/bindings.rs b/rust/qemu-api/src/bindings.rs
index 6e70a75a0e..b791ca6d87 100644
--- a/rust/qemu-api/src/bindings.rs
+++ b/rust/qemu-api/src/bindings.rs
@@ -40,9 +40,6 @@ unsafe impl Sync for MemoryRegion {}
 unsafe impl Send for ObjectClass {}
 unsafe impl Sync for ObjectClass {}
 
-unsafe impl Send for SysBusDevice {}
-unsafe impl Sync for SysBusDevice {}
-
 // SAFETY: this is a pure data struct
 unsafe impl Send for CoalescedMemoryRange {}
 unsafe impl Sync for CoalescedMemoryRange {}
diff --git a/rust/qemu-api/src/sysbus.rs b/rust/qemu-api/src/sysbus.rs
index 0790576d44..e92502a8fe 100644
--- a/rust/qemu-api/src/sysbus.rs
+++ b/rust/qemu-api/src/sysbus.rs
@@ -6,11 +6,11 @@
 
 use std::{ffi::CStr, ptr::addr_of_mut};
 
-pub use bindings::{SysBusDevice, SysBusDeviceClass};
+pub use bindings::SysBusDeviceClass;
 
 use crate::{
     bindings,
-    cell::bql_locked,
+    cell::{bql_locked, Opaque},
     irq::{IRQState, InterruptSource},
     memory::MemoryRegion,
     prelude::*,
@@ -18,6 +18,14 @@ use crate::{
     qom::Owned,
 };
 
+/// A safe wrapper around [`bindings::SysBusDevice`].
+#[repr(transparent)]
+#[derive(Debug, qemu_api_macros::Wrapper)]
+pub struct SysBusDevice(Opaque<bindings::SysBusDevice>);
+
+unsafe impl Send for SysBusDevice {}
+unsafe impl Sync for SysBusDevice {}
+
 unsafe impl ObjectType for SysBusDevice {
     type Class = SysBusDeviceClass;
     const TYPE_NAME: &'static CStr =
@@ -49,7 +57,7 @@ where
     fn init_mmio(&self, iomem: &MemoryRegion) {
         assert!(bql_locked());
         unsafe {
-            bindings::sysbus_init_mmio(self.as_mut_ptr(), iomem.as_mut_ptr());
+            bindings::sysbus_init_mmio(self.upcast().as_mut_ptr(), iomem.as_mut_ptr());
         }
     }
 
@@ -60,14 +68,16 @@ where
     fn init_irq(&self, irq: &InterruptSource) {
         assert!(bql_locked());
         unsafe {
-            bindings::sysbus_init_irq(self.as_mut_ptr(), irq.as_ptr());
+            bindings::sysbus_init_irq(self.upcast().as_mut_ptr(), irq.as_ptr());
         }
     }
 
     // TODO: do we want a type like GuestAddress here?
     fn mmio_addr(&self, id: u32) -> Option<u64> {
         assert!(bql_locked());
-        let sbd = self.upcast();
+        // SAFETY: the BQL ensures that no one else writes to sbd.mmio[], and
+        // the SysBusDevice must be initialized to get an IsA<SysBusDevice>.
+        let sbd = unsafe { *self.upcast().as_ptr() };
         let id: usize = id.try_into().unwrap();
         if sbd.mmio[id].memory.is_null() {
             None
@@ -81,7 +91,7 @@ where
         assert!(bql_locked());
         let id: i32 = id.try_into().unwrap();
         unsafe {
-            bindings::sysbus_mmio_map(self.as_mut_ptr(), id, addr);
+            bindings::sysbus_mmio_map(self.upcast().as_mut_ptr(), id, addr);
         }
     }
 
@@ -93,7 +103,7 @@ where
         let id: i32 = id.try_into().unwrap();
         let irq: &IRQState = irq;
         unsafe {
-            bindings::sysbus_connect_irq(self.as_mut_ptr(), id, irq.as_mut_ptr());
+            bindings::sysbus_connect_irq(self.upcast().as_mut_ptr(), id, irq.as_mut_ptr());
         }
     }
 
@@ -101,7 +111,10 @@ where
         // TODO: return an Error
         assert!(bql_locked());
         unsafe {
-            bindings::sysbus_realize(self.as_mut_ptr(), addr_of_mut!(bindings::error_fatal));
+            bindings::sysbus_realize(
+                self.upcast().as_mut_ptr(),
+                addr_of_mut!(bindings::error_fatal),
+            );
         }
     }
 }
-- 
2.39.5