Re: [Qemu-devel] Re: [PATCH v3 0/2] Inter-VM shared memory PCI device

[Cam Macdonell]

On Thu, Mar 25, 2010 at 7:32 PM, Jamie Lokier <address@hidden> wrote:
> Cam Macdonell wrote:
>> An irqfd can only trigger a single vector in a guest.  Right now I
>> only have one eventfd per guest.    So ioeventfd/irqfd restricts the
>> current implementation to a single vector that a guest can trigger.
>> Without irqfd, eventfds can be used like registers a write the number
>> of the vector they want to trigger, but as you point out it is racy.
>
> It's not racy if you use a pipe instead of eventfd. :-)
>
> Actually, why not?  A byte pipe between guests would be more versatile.

A pipe between guests would be quite versatile, however it's an
orthogonal design to shared memory.    The shared memory is how data
should be shared/communicated if someone is using this device and the
interrupts are there to help with synchronization.

>
> Could it even integrate with virtio-serial, somehow?
>

Could virtio-serial be used as is to support a pipe between guests?

If a user wanted shared memory and a pipe, then they could setup two
devices and use them together.

Cam