On Thu, Feb 27, 2025 at 03:22:11PM +0100, Paolo Bonzini wrote:
> Date: Thu, 27 Feb 2025 15:22:11 +0100
> From: Paolo Bonzini <pbonz...@redhat.com>
> Subject: [PATCH 04/12] rust: timer: wrap QEMUTimer with Opaque<> and
> express pinning requirements
> X-Mailer: git-send-email 2.48.1
>
> Timers must be pinned in memory, because modify() stores a pointer to them
> in the TimerList. To ensure this is the case, replace the separate new()
> and init_full() with a single function that returns a pinned box. Because
> the only way to obtain a Timer is through Timer::new_full(), modify()
> knows that the timer it got is also pinned. In the future the pinning
> requirement will be expressed through the pin_init crate instead.
>
> Note that Timer is a bit different from other users of Opaque, in that
> it is created in Rust code rather than C code. This is why it has to
> use the unsafe Opaque::new() function.
>
> Signed-off-by: Paolo Bonzini <pbonz...@redhat.com>
> ---
> meson.build | 7 -----
> rust/hw/timer/hpet/src/hpet.rs | 23 ++++++++---------
> rust/qemu-api/src/timer.rs | 47 ++++++++++++++++++++++------------
> 3 files changed, 41 insertions(+), 36 deletions(-)
Great! LGTM,
Reviewed-by: Zhao Liu <zhao1....@intel.com>
(But pls wait, I have a question below...)
> @@ -156,7 +157,7 @@ pub struct HPETTimer {
> /// timer N index within the timer block (`HPETState`)
> #[doc(alias = "tn")]
> index: usize,
> - qemu_timer: Option<Box<Timer>>,
> + qemu_timer: Option<Pin<Box<Timer>>>,
I'm removing this Option<> wrapper in migration series. This is because
Option<> can't be treated as pointer as you mentioned in [*].
So for this reason, does this mean that VMStateField cannot accept
Option<>? I realize that all the current VMStateFlags don't seem
compatible with Option<> unless a new flag is introduced.
[*]:
https://lore.kernel.org/qemu-devel/9a0389fa-765c-443b-ac2f-7c99ed862...@redhat.com/
Thanks,
Zhao
