Re: [Qemu-devel] [PATCH] Vmchannel PCI device.

Gleb Natapov
2008-12-14T19:36:50Z

On Sun, Dec 14, 2008 at 01:15:42PM -0600, Anthony Liguori wrote:
> Gleb Natapov wrote:
>> On Sun, Dec 14, 2008 at 02:28:23PM +0200, Blue Swirl wrote:
>>
>>> On 12/14/08, Gleb Natapov <gleb@redhat.com> wrote:
>>>
>>>> There is a need for communication channel between host and various
>>>> agents that are running inside a VM guest. The channel will be used
>>>> for statistic gathering, logging, cut & paste, host screen resolution
>>>> changes notification, guest configuration etc.
>>>>
>>> Isn't this exactly what the firmware configuration device was supposed
>>> to be used for? In the list of use cases you gave, I don't see
>>> anything that could not be done with it.
>>>
>>>
>> The requirement for firmware configuration interface was different. We
>> wanted something simple that we can use as early as possible in cpu init
>> code and performance was not considered at all. Obviously PCI device doesn't
>> fit for this. We don't want to write PCI driver inside a BIOS and PCI
>> initialization is too late in HW initialization sequence.
>>
>> The requirement for vmchannel was that it should allow a guest
>> to communicate with external (to qemu) process and with reasonable
>> performance too.
>
> This is not a requirement that I think is important. It's only a
> requirement for you because you have closed code that you want to
> implement the backend with. I would personally be more interested in
> vmchannel backends in QEMU and I think there will be a lot of them.
>
I don't know why do you think that we are going to use that for closed
code or something. It will be used by libvirt and it is open source last
I checked.

--
Gleb.