Re: [Qemu-devel] qemu virtIO blocking operation - question

[Stefan Hajnoczi]

On Mon, Sep 12, 2011 at 7:31 PM, Sinha, Ani <address@hidden> wrote:
>
> On Sep 11, 2011, at 6:34 AM, Stefan Hajnoczi wrote:
>
>> On Fri, Sep 09, 2011 at 07:45:17PM -0500, Sinha, Ani wrote:
>>> So I am writing a virtIO driver for a device that supports blocking calls 
>>> like poll() etc. Now the front end paravirtualized driver mirrors the 
>>> request to the backend "host" qemu process that then does the actual call 
>>> on the host kernel on behalf of the guest. Now my question is, when I do a 
>>> blocking call from within the callback that I have registered when I 
>>> created the virtqueue, does it block the entire vcpu? If it does, do I have 
>>> to create an async context for it? Looking at virtio-net and virtio-block, 
>>> I can see the concept of bottom halves but I am not sure if this helps me 
>>> in any way.
>>
>> What device are you adding?  It would help to share what you are trying
>> to accomplish.
>
>
> We are trying to paravirtualize the IPMI device (/dev/ipmi0).

>From http://en.wikipedia.org/wiki/Intelligent_Platform_Management_Interface:
"An implementation of IPMI version 1.5 can communicate via a direct
serial connection or via a side-band local area network (LAN)
connection to a remote client."

Why do you need a new virtio device?  Can't you use virtio-serial?
This is what other management channels are using for host<->guest
agents.

What features and use cases does paravirtualized IPMI provide?

Stefan