Re: Inter VM Communication

[Anthony Liguori <anthony@codemonkey.ws>]

Avi Kivity wrote:
> Kumar, Venkat wrote:
>> Just like how Xen has Xenbus, Emulated Platform-PCI device and Events 
>> for Inter VM communication, Does KVM has any mechanism for Inter VM 
>> communication? How to share a page between two virtual machines 
>> running on KVM?
>>   
>
> If you just want to share a page (or a bunch of memory), write a qemu 
> PCI device model that exposes that page through a BAR.  The guests can 
> then map the BAR and access the page.

So one gotcha about using a BAR is that we emulate a 32-bit PCI device 
so that limits where the BAR can live in memory and how large it can be.

I think bars also have to be powers of two in size.

Regards,

Anthony Liguori

> To share the page, use normal Linux memory sharing, such as shared 
> memory segments or mapped files (possibly on /dev/shm).
>
> Note that sharing will break as soon as one of the guests is migrated 
> away.
>
> To send events you can utilize pci interrupts.
>
> An alternative approach is to use virtio, but this is somewhat more 
> complicated.
>