Re: [Xen-devel] [XenSummit 2017] Shared coprocessor framework followup

[Andrii Anisov <andrii_anisov@xxxxxxxx>]

Hello Edgar,


On 01.08.17 20:13, Edgar E. Iglesias wrote:
> > Are master ports behind IOMMU?
> Yes, they are.
What IOMMU IP is used?

> > > It's possible to reprogram the configuration of the PL and swap accelerators in
> > > and out on the fly. It's probably going to be too slow for trying to
> > > context switch between guests
> > So let us assume it is a FW-less resource we need to share between domains.
> > Context switch will be stripped to mapping its mmio (or passing mmio
> > accesses) next domain to serve and IOMMU configuration switching.
> > Yep, IOMMU matters.
> OK. I think the PL is more like a firmware enabled resource.
> The PL configuration needs to be loaded much like firmware
> otherwise the accelerators can't change shape and all guests
> must use the same kind.
I understand this.
But I got your words like you are going to give a try to the same kind 
for all domains first. Because you assumed that reconfiguring would be 
too slow, what is actually discussable.
> > >   so I think primarily we would be looking at
> > > a way to lets say, "allocate" and "release" the resources for batch use.
> > Kind of voluntary preemption?
> Right. That could be a start.
> In the future perhaps it makes sense to context-switch.
We still need the context switch to be done. The difference is that now 
it could be done only when the accelerator is not busy.
> > > If a guest cannot allocate an accelerator, it could fall back to emulation
> > > or just to using SW libraries until an accelerator slot is available.
> > What about the thing I called "an access emulation" [1]? From the domain's
> > point of view it would be reflected in a delayed response (via IRQ or
> > register polling) from an accelerator.
> >
> > I guess the concept described above is feasible even with current SCF code
> > and will not take too much efforts.
> I'll have a look, thanks!
Do not hesitate to contact us in case you need any help or clarification.


--

*Andrii Anisov*


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel