inter-VM communication?

inter-VM communication?

[Jun Koi]

Hi,

Do we have any inter-VM communication technique in KVM (something for
example like event-channel in Xen) ?

Thanks,
Jun

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Re: inter-VM communication?

[Dor Laor]

> Hi,
> 
> Do we have any inter-VM communication technique in KVM (something for
> example like event-channel in Xen) ?
> 
> Thanks,
> Jun

Currently there is full isolation of the guests.
Such mechanism would not be complicated to add since we anyway map
memory from user space & inject interrupt from there also.
Do you have any specific interest in inter VM channel?

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Re: inter-VM communication?

[Jun Koi]

On 11/30/06, Dor Laor <dor.laor-atKUWr5tajBWk0Htik3J/w@public.gmane.org> wrote:
> > Hi,
> >
> > Do we have any inter-VM communication technique in KVM (something for
> > example like event-channel in Xen) ?
> >
> > Thanks,
> > Jun
>
> Currently there is full isolation of the guests.
> Such mechanism would not be complicated to add since we anyway map
> memory from user space & inject interrupt from there also.
> Do you have any specific interest in inter VM channel?

I want to exchange some data between a VM and hypervisor. One solution
is to map some memory of that VM (from hypervisor), and read/write
data thru that memory area. However, I need to a mechanism to notify
the other partner when data is ready to read/write.

Without any inter-VM communication mechanism, I dont see any clean way
to achieve this. Any idea?

Thanks,
Jun

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Re: inter-VM communication?

[Avi Kivity]

Jun Koi wrote:
> On 11/30/06, Dor Laor <dor.laor-atKUWr5tajBWk0Htik3J/w@public.gmane.org> wrote:
>   
>>> Hi,
>>>
>>> Do we have any inter-VM communication technique in KVM (something for
>>> example like event-channel in Xen) ?
>>>
>>> Thanks,
>>> Jun
>>>       
>> Currently there is full isolation of the guests.
>> Such mechanism would not be complicated to add since we anyway map
>> memory from user space & inject interrupt from there also.
>> Do you have any specific interest in inter VM channel?
>>     
>
> I want to exchange some data between a VM and hypervisor. One solution
> is to map some memory of that VM (from hypervisor), and read/write
> data thru that memory area. However, I need to a mechanism to notify
> the other partner when data is ready to read/write.
>
> Without any inter-VM communication mechanism, I dont see any clean way
> to achieve this. Any idea?
>   

Write a pci device for qemu to do what you want.  The pci device can 
communicate through a unix domain socket, shared memory, or any other 
ipc mechanism with any other process on the host (including other 
virtual machines).

Guest->host communication is performed by writing the device's mmio 
registers.  Host->guest communications are done by raising a virtual 
interrupt.

-- 
error compiling committee.c: too many arguments to function


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Re: inter-VM communication?

[Dor Laor]

> Jun Koi wrote:
> > On 11/30/06, Dor Laor <dor.laor-atKUWr5tajBWk0Htik3J/w@public.gmane.org> wrote:
> >
> >>> Hi,
> >>>
> >>> Do we have any inter-VM communication technique in KVM (something
for
> >>> example like event-channel in Xen) ?
> >>>
> >>> Thanks,
> >>> Jun
> >>>
> >> Currently there is full isolation of the guests.
> >> Such mechanism would not be complicated to add since we anyway map
> >> memory from user space & inject interrupt from there also.
> >> Do you have any specific interest in inter VM channel?
> >>
> >
> > I want to exchange some data between a VM and hypervisor. One
solution
> > is to map some memory of that VM (from hypervisor), and read/write
> > data thru that memory area. However, I need to a mechanism to notify
> > the other partner when data is ready to read/write.
> >
> > Without any inter-VM communication mechanism, I dont see any clean
way
> > to achieve this. Any idea?
> >
> 
> Write a pci device for qemu to do what you want.  The pci device can
> communicate through a unix domain socket, shared memory, or any other
> ipc mechanism with any other process on the host (including other
> virtual machines).
> 
> Guest->host communication is performed by writing the device's mmio
> registers.  Host->guest communications are done by raising a virtual
> interrupt.

If you would like a reference for writing such device, there was a
thread in the Qemu mailing list about such interface:
http://lists.gnu.org/archive/html/qemu-devel/2006-11/msg00149.html

Such an interface is on the roadmap but quick patches would certainly
help :)


> 
> --
> error compiling committee.c: too many arguments to function


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