Re: [PATCH] Add shared memory PCI device that shares a memory object betweens VMs

[Cam Macdonell <cam@cs.ualberta.ca>]

subbu kl wrote:
> correct me if wrong,
> can we do the sharing business by writing a non-transparent qemu PCI 
> device in host and guests can access each other's address space ?

Hi Subbu,

I'm a bit confused by your question.  Are you asking how this device 
works or suggesting an alternative approach?  I'm not sure what you mean 
by a non-transparent qemu device.

Cam

> 
> ~subbu
> 
> On Sun, Apr 19, 2009 at 3:56 PM, Avi Kivity <avi@redhat.com 
> <mailto:avi@redhat.com>> wrote:
> 
>     Cameron Macdonell wrote:
> 
> 
>         Hi Avi and Anthony,
> 
>         Sorry for the top-reply, but we haven't discussed this aspect
>         here before.
> 
>         I've been thinking about how to implement interrupts.  As far as
>         I can tell, unix domain sockets in Qemu/KVM are used
>         point-to-point with one VM being the server by specifying
>         "server" along with the unix: option.  This works simply for two
>         VMs, but I'm unsure how this can extend to multiple VMs.  How
>         would a server VM know how many clients to wait for?  How can
>         messages then be multicast or broadcast?  Is a separate
>         "interrupt server" necessary?
> 
> 
> 
>     I don't think unix provides a reliable multicast RPC.  So yes, an
>     interrupt server seems necessary.
> 
>     You could expand its role an make it a "shared memory PCI card
>     server", and have it also be responsible for providing the backing
>     file using an SCM_RIGHTS fd.  That would reduce setup headaches for
>     users (setting up a file for which all VMs have permissions).
> 
>     -- 
>     Do not meddle in the internals of kernels, for they are subtle and
>     quick to panic.
> 
> 
>     --
>     To unsubscribe from this list: send the line "unsubscribe kvm" in
>     the body of a message to majordomo@vger.kernel.org
>     <mailto:majordomo@vger.kernel.org>
>     More majordomo info at  http://vger.kernel.org/majordomo-info.html
> 
> 
> 
> 
> -- 
> ~subbu