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Re: [Qemu-devel] New Memory API Question
From: |
Avi Kivity |
Subject: |
Re: [Qemu-devel] New Memory API Question |
Date: |
Thu, 27 Oct 2011 12:23:54 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:7.0.1) Gecko/20110930 Thunderbird/7.0.1 |
On 10/26/2011 03:52 PM, John Baboval wrote:
> Sorry for coming late to the party on this... I only read qemu-devel
> through a filter so I missed all the discussions on the new memory
> API. I have a question as to how it works and how it's supposed to
> work in certain scenarios.
>
> It's a question of flow. I'm following the code path through the
> creation of a new memory subregion. If I'm reading this properly, it
> would seem that a MemoryRegion - for example the ones used by VGA - go
> through the following flow:
>
> memory_region_init_ram() - (mr->destructor is set to
> memory_region_destructor_ram)
> memory_region_add_subregion(system_memory, ...) ->
> memory_region_update_topology() ->
> address_space_update_topology()
> address_space_update_topology_part()
> as_memory_range_add() - through the ops vector
> memory_region_prepare_ram_addr()
>
>
> At this point it seems that the destructor is overwritten with the
> memory_region_destructor_iomem(), and it loses track of the proper way
> to ever free the memory region. Is this correct, or am I missing
> something?
It's correct; this is a bug.
>
> Or does it not matter because nobody ever calls memory_region_destroy
> for system memory regions?
It can still happen via hotunplug of an ivshmem device, or memory
hotunplug (when it is eventually implemented).
--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.