Interrupt sources, qemu_irq in C code, are pointers to IRQState objects. They are QOM link properties and can be written to outside the control of the device (i.e. from a shared reference); therefore their Rust representation must be an interior-mutable field.
This make interrupt sources similar to a Cell<*mut IRQState>. However, a Cell can only live within one thread, while here the semantics are "accessible by multiple threads but only under the Big QEMU Lock". Therefore, this series adds to QEMU a specialized cell type that checks locking rules with respect to the "Big QEMU Lock". In particular, qemu_api::cell::BqlCell only allows get()/set() under BQL protection and therefore is Send/Sync. It comes with documentation and doctests. I am not fully satisfied with the solution I used for mocking the BQL; I have a prototype that runs doctests from "meson test" but that may take some more time to cook. Likewise, qemu_api::cell::RefCell would be a RefCell that is Send/Sync, because it checks that borrow()/borrow_mut() is only done under BQL; but this is not added here because there is no use case (yet). The interrupt sources prat was previously posted as RFC at https://lore.kernel.org/qemu-devel/20241104085159.76841-1-pbonz...@redhat.com/, while the BqlCell is new. The code is a bit long but most of it is lifted from the standard library and almost half is documentation. Please review! Paolo Bonzini (2): rust: add BQL-enforcing Cell variant rust: add bindings for interrupt sources rust/hw/char/pl011/src/device.rs | 22 +-- rust/qemu-api/meson.build | 3 + rust/qemu-api/src/cell.rs | 294 +++++++++++++++++++++++++++++++ rust/qemu-api/src/irq.rs | 66 +++++++ rust/qemu-api/src/lib.rs | 3 + rust/qemu-api/src/sysbus.rs | 26 +++ 6 files changed, 404 insertions(+), 10 deletions(-) create mode 100644 rust/qemu-api/src/cell.rs create mode 100644 rust/qemu-api/src/irq.rs create mode 100644 rust/qemu-api/src/sysbus.rs -- 2.47.0
