We have some users of the PL011 struct which embed it directly into
their own state structs. This means that the Rust version of the
device must have a state struct that is the same size or smaller
than the C struct.
In commit 9b642097d6 ("rust: pl011: switch to safe chardev operation")
the Rust PL011 state struct changed from having a bindings::CharBackend
to a chardev::CharBackend, which made it grow larger than the C
version. This results in an assertion at startup when QEMU was
built with Rust enabled:
$ qemu-system-arm -M raspi2b -display none
ERROR:../../qom/object.c:562:object_initialize_with_type: assertion
failed: (size >= type->instance_size)
The long-term better approach to this problem would be to move
our C device code patterns away from "embed a struct" and (back)
to "have a pointer to the device", so we can make the C PL011State
struct a private implementation detail rather than exposed to
its users.
For the short term, add a padding field at the end of the C struct
so it's big enough that the Rust state struct can fit.
Fixes: 9b642097d6 ("rust: pl011: switch to safe chardev operation")
Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Link: https://lore.kernel.org/r/20250321112523.1774131-3-peter.maydell@linaro.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
5b87a07e76