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rust: qdev: add clock creation

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Add a Rust version of qdev_init_clock_in, which can be used in
instance_init.  There are a couple differences with the C
version:

- in Rust the object keeps its own reference to the clock (in addition to
  the one embedded in the NamedClockList), and the reference is dropped
  automatically by instance_finalize(); this is encoded in the signature
  of DeviceClassMethods::init_clock_in, which makes the lifetime of the
  clock independent of that of the object it holds.  This goes unnoticed
  in the C version and is due to the existence of aliases.

- also, anything that happens during instance_init uses the pinned_init
  framework to operate on a partially initialized object, and is done
  through class methods (i.e. through DeviceClassMethods rather than
  DeviceMethods) because the device does not exist yet.  Therefore, Rust
  code *must* create clocks from instance_init, which is stricter than C.

Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2025-01-17 11:21:26 +01:00
parent 66bcc554d2
commit 201ef001dd
4 changed files with 125 additions and 31 deletions
Download patch file Download diff file Expand all files Collapse all files

43
rust/hw/char/pl011/src/device.rs
View file

@ -10,17 +10,16 @@ use std::{
use qemu_api::{
bindings::{
error_fatal, hwaddr, memory_region_init_io, qdev_init_clock_in, qdev_prop_set_chr,
qemu_chr_fe_accept_input, qemu_chr_fe_ioctl, qemu_chr_fe_set_handlers,
qemu_chr_fe_write_all, qemu_irq, sysbus_connect_irq, sysbus_mmio_map, sysbus_realize,
CharBackend, Chardev, Clock, ClockEvent, MemoryRegion, QEMUChrEvent,
CHR_IOCTL_SERIAL_SET_BREAK,
error_fatal, hwaddr, memory_region_init_io, qdev_prop_set_chr, qemu_chr_fe_accept_input,
qemu_chr_fe_ioctl, qemu_chr_fe_set_handlers, qemu_chr_fe_write_all, qemu_irq,
sysbus_connect_irq, sysbus_mmio_map, sysbus_realize, CharBackend, Chardev, MemoryRegion,
QEMUChrEvent, CHR_IOCTL_SERIAL_SET_BREAK,
},
c_str, impl_vmstate_forward,
irq::InterruptSource,
prelude::*,
qdev::{DeviceImpl, DeviceState, Property},
qom::{ClassInitImpl, ObjectImpl, ParentField},
qdev::{Clock, ClockEvent, DeviceImpl, DeviceState, Property},
qom::{ClassInitImpl, ObjectImpl, Owned, ParentField},
sysbus::{SysBusDevice, SysBusDeviceClass},
vmstate::VMStateDescription,
};
@ -131,7 +130,7 @@ pub struct PL011State {
#[doc(alias = "irq")]
pub interrupts: [InterruptSource; IRQMASK.len()],
#[doc(alias = "clk")]
pub clock: NonNull<Clock>,
pub clock: Owned<Clock>,
#[doc(alias = "migrate_clk")]
pub migrate_clock: bool,
}
@ -485,8 +484,6 @@ impl PL011State {
/// location/instance. All its fields are expected to hold unitialized
/// values with the sole exception of `parent_obj`.
unsafe fn init(&mut self) {
const CLK_NAME: &CStr = c_str!("clk");
// SAFETY:
//
// self and self.iomem are guaranteed to be valid at this point since callers
@ -506,22 +503,16 @@ impl PL011State {
// SAFETY:
//
// self.clock is not initialized at this point; but since `NonNull<_>` is Copy,
// we can overwrite the undefined value without side effects. This is
// safe since all PL011State instances are created by QOM code which
// calls this function to initialize the fields; therefore no code is
// able to access an invalid self.clock value.
unsafe {
let dev: &mut DeviceState = self.upcast_mut();
self.clock = NonNull::new(qdev_init_clock_in(
dev,
CLK_NAME.as_ptr(),
None, /* pl011_clock_update */
addr_of_mut!(*self).cast::<c_void>(),
ClockEvent::ClockUpdate.0,
))
.unwrap();
}
// self.clock is not initialized at this point; but since `Owned<_>` is
// not Drop, we can overwrite the undefined value without side effects;
// it's not sound but, because for all PL011State instances are created
// by QOM code which calls this function to initialize the fields, at
// leastno code is able to access an invalid self.clock value.
self.clock = self.init_clock_in("clk", &Self::clock_update, ClockEvent::ClockUpdate);
}
const fn clock_update(&self, _event: ClockEvent) {
/* pl011_trace_baudrate_change(s); */
}
fn post_init(&self) {