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Date: Wed, 22 Oct 2014 09:12:48 +0200
From: Max Reitz <mreitz@redhat.com>
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Subject: Re: [Qemu-devel] writing a QEMU block driver
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To: Sandeep Joshi <sanjos100@gmail.com>
Cc: qemu-devel@nongnu.org

On 2014-10-22 at 05:08, Sandeep Joshi wrote:
>
> Another small question.   I noticed that all block drivers call 
> block_init ("module_init") and qemu_system binary has the 
> "--enable-modules" command line option.
>
> But does QEMU support building block drivers outside the main source 
> tree ?   And can I load a new block driver module into running QEMU 
> system - like the Linux kernel allows ?   Or do I have to distribute 
> an entire own QEMU image if I add a new driver ?  I am not sure if 
> what I am asking is the same as https://wiki.ubuntu.com/QemuDiskHotplug

No, this is a different question. Disk hotplug is something for the 
guest, whereas you want something for the host. As far as I know, people 
are aware of that issue and it may be implemented at some point in time. 
But right now it's not supported in vanilla qemu (I've heard something 
about at least one distribution already having implemented this).

If you add a new driver, you either have to distribute its source so 
people can build qemu themselves with the driver included; or you build 
qemu yourself and then distribute the binary; or you find your driver 
good enough to submit it for upstream qemu.

Max