Re: [Qemu-devel] [PATCH] exec.c: check RAMBlock validity before changing its flag

[Paolo Bonzini]

On 04/07/2018 11:55, Peter Xu wrote:
>>     commit b0e56e0b63f350691b52d3e75e89bb64143fbeff
>>     Author: Hu Tao <address@hidden>
>>     Date:   Wed Apr 2 15:13:27 2014 +0800
>>
>>     unset RAMBlock idstr when unregister MemoryRegion
>>
>>     Signed-off-by: Hu Tao <address@hidden>
>>     Signed-off-by: Paolo Bonzini <address@hidden>
>>
>> whose commit message is a bit lacking, but
>> http://lists.gnu.org/archive/html/qemu-devel/2014-04/msg00282.html helps
>> more.  It seems like the original bug was a reference count issue.
>>
>> Clearing the new migratable flag should also be unnecessary.
> But even if we get rid of vmstate_unregister_ram(), the leak could
> still be there?
> 
> I'm not sure what was leaked when b0e56e0b6 was introduced, I feel
> like it's the RAMBlock of the memdev.  Here I think the ROM memory
> region seems to be leaked as well (along with the RAMBlock inside)?

The leak would be another bug that vmstate_unregister_ram is just
papering over.  We need to test memory unplug with
vmstate_unregister_ram removed, and fix bugs if any.

Paolo