Re: [Qemu-devel] [PATCH 28/40] xenner: libxc emu: evtchn

[Alexander Graf]

On 01.11.2010, at 12:01, Anthony Liguori wrote:

> On 11/01/2010 10:49 AM, Alexander Graf wrote:
>> On 01.11.2010, at 11:45, Anthony Liguori wrote:
>> 
>>   
>>> On 11/01/2010 10:01 AM, Alexander Graf wrote:
>>>     
>>>> Xenner emulates parts of libxc, so we can not use the real xen 
>>>> infrastructure
>>>> when running xen pv guests without xen.
>>>> 
>>>> This patch adds support for event channel communication.
>>>> 
>>>> Signed-off-by: Alexander Graf<address@hidden>
>>>> 
>>>>       
>>> Has anyone checked with the Xen folks about supporting this type of 
>>> functionality in libxc directly?
>>>     
>> 
>> The issue I have with libxc is that it goes orthogonal to the qemu 
>> infrastructure way of doing things. If we base on libxc, we will never be 
>> able to do cross-architecture execution of xen pv guests. Do we really want 
>> to go that way?
>>   
> 
> IIUC, this is a mini-libxc that you enable by mucking with LD_LIBRARY_PATH 
> such that you can run things like xenstored unmodified.  What I'm really 
> asking is whether there has been a discussion about a more pleasant way to do 
> this that the Xen guys would feel comfortable with.
> 
> I'd feel a little weird if someone was replacing a part of QEMU via 
> LD_LIBRARY_PATH trickery.  It's better to try to work out a proper solution 
> with the upstream community than to do trickery.
> 
> I'm not entirely opposed to this if the Xen guys say they don't want anything 
> to do with Xenner, but we should have the discussion at least.

I agree about the discussion part, that's why we're all gathering in Boston 
this week, right?

But technically, this code really just bumps all libxc calls to indirect 
function calls that go through a struct. If we're using xenner, we use our own 
implementation, if we're using xen, we use xen's. The thing is that with xenner 
we usually don't have xen infrastructure available and most likely don't want 
to start any either.


Alex