Re: [RFC][PATCH 0/4] arm64:kvm: teach guest sched that VCPUs can be preempted

[Joel Fernandes]

On Fri, Sep 11, 2020 at 4:58 AM Sergey Senozhatsky
<sergey.senozhatsky@xxxxxxxxx> wrote:
>
> My apologies for the slow reply.
>
> On (20/08/17 13:25), Marc Zyngier wrote:
> >
> > It really isn't the same thing at all. You are exposing PV spinlocks,
> > while Sergey exposes preemption to vcpus.
> >
>
> Correct, we see vcpu preemption as a "fundamental" feature, with
> consequences that affect scheduling, which is a core feature :)
>
> Marc, is there anything in particular that you dislike about this RFC
> patch set? Joel has some ideas, which we may discuss offline if that
> works for you.

Hi Marc, Sergey, Just checking what is the latest on this series?

About the idea me and Sergey discussed, at a high level we discussed
being able to share information similar to "Is the vCPU preempted?"
using a more arch-independent infrastructure. I do not believe this
needs to be arch-specific. Maybe the speciifc mechanism about how to
share a page of information needs to be arch-specific, but the actual
information shared need not be. This could open the door to sharing
more such information in an arch-independent way (for example, if the
scheduler needs to know other information such as the capacity of the
CPU that the vCPU is on).

Other thoughts?

thanks,

 - Joel