Similar to MemoryRegionOps, the builder pattern has two advantages:
1) it makes it possible to build a VMStateDescription that knows which
types it will be invoked on; 2) it provides a way to wrap the callbacks
and let devices avoid "unsafe".
Unfortunately, building a static VMStateDescription requires the
builder methods to be "const", and because the VMStateFields are
*also* static, this requires const_refs_static. So this requires
Rust 1.83.0.
Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
Link: https://lore.kernel.org/r/20250908105005.2119297-8-pbonzini@redhat.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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