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Subject: Re: [virtio-dev] Memory sharing device

> > > In general though, this means that the ideal usage of host pointers would
> > > be to set a few regions up front for certain purposes, then share that
> > out
> > > amongst other device contexts. This also facilitates sharing the memory
> > > between guest processes, which is useful for implementing things like
> > > compositors.
> >
> > Guest processes in the same VM or in different VMs?
> >
> The guest processes are in the same VM.
> Are you also considering the usage in different VMs?

No, I'm just asking whenever that is important to you.

For communication between guest processes within the same VM I don't
really see a need to involve the hypervisor ...

> > This also features heavily for our "virtio userspace" thing.
> > > Since this is a common pattern, should this sharing concept be
> > standardized
> > > somehow? I.e., should there be a standard way to send Shmid/offset/size
> > to
> > > other devices, or have that be a standard struct in the hypervisor?
> >
> > Same question: other devices of the same VM?
> >
> Yes, also, other devices of the same VM.

So why involve the hypervisor here?  The guest can handle that on its
own.  Passing an image data buffer from the usb webcam to the intel gpu
for display (on bare metal) isn't fundamentally different from passing a
buffer from virtio-camera to virtio-gpu (in a VM).  Linux guests will
use dma-bufs for that, other OSes probably something else.


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