Re: [Qemu-devel] [PATCH] vmstate: Add VMSTATE_OPAQUE to save/load complex data structures

[Roman Kiryanov]

Hi Dave, thank you for looking.

> Can you give me an example of where you would use it?

We use it in our host memory sharing device. I used the existing
macros for all fields I could, but unfortunately some state does not fit
into them. We use this new macro to save/load memory
allocators (for now we have malloc, but we are working on adding
Vulkan calls). For now the state looks this way:

class Allocator;
unordered_map<int, Allocator *> state;

class MallocAllocator: public Allocator {
    unordered_map<int, vector<char>> state;
};

class VulkanAllocator: public Allocator {
    // TBD
};

>  I've been trying to get rid as many of the open-coded cases as possible

I saw this in the migration document. I used VMSTATE_INT32,
VMSTATE_STRUCT and VMSTATE_STRUCT_VARRAY_ALLOC
where I could.

> Having said that;  would it be easier to pass the get/put functions
> rather than the info ?

Sure, function pointer will be even better, but since VMStateField
takes "const VMStateInfo *", I added this way.

Regards,
Roman.