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Re: [libvirt] [PATCH v1 1/6] doc: schema: Add documentation for the shmem support

On Tue, Aug 26, 2014 at 8:22 AM, Martin Kletzander <mkletzan redhat com> wrote:
> On Fri, Aug 22, 2014 at 12:47:00PM +0200, Maxime Leroy wrote:
>> Considering there could be other shared memory related devices,
>> this patch introduces a general device model, called shmem device.
>> Currenly "ivshmem" is the only shared memory model supported.
> Automatically adding model='ivshmem' takes away the generality gained
> by renaming the device.  Especially if it is the only model supported
> we don't have to put "model" in there.

Model is an optional attribute. You can still use this xml: <shmem name="asdf"/>

> If we expand this to another
> device/hypervisor, we then might separate the setting by a model and
> automatically add model='ivshmem', but we might keep it the same if
> the options will compatible.  Until then the model specification just
> adds unnecessary code.

It's the same concept from this first implementation of ivshmem:

Having a model attribute allow to split properly the code specific to
a generic shared memory concept and the code specific to ivshmem.

There are pros and cons to have or not a model attribute.

Anyway, let keep the code simple by removing the model attribute.

>> About ivshmem, please see the following documentation:
>> http://git.qemu.org/?p=qemu.git;a=blob;f=docs/specs/ivshmem_device_spec.txt
>> (Ivshmem documentation for qemu will be updated soon:
>> http://lists.gnu.org/archive/html/qemu-devel/2014-08/msg01244.html)
>> In the devices section in the domain XML users may specify:
>> - For ivshmem device using an ivshmem server:
>> <shmem name='shmem0' model='ivshmem'>
>>   <source file='/tmp/socket-ivshmem0'/>
>>   <size unit='M'>32</size>
>>   <msi vectors='32' ioeventfd='on'/>
>> </shmem>
> From the documentation you've linked I understand it that either the
> ivshmem has a name *or* it uses a server; and then it doesn't need a
> name because the server sends an FD to the shared memory using

The name is not needed if libvirt doesn't start the ivshmem server. In
this case, it could be optional.


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