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

[Avi Kivity <avi@redhat.com>]

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.