Re: [Xen-devel] Hypervisor to dom0 communication

[Tim Deegan <tim@xxxxxxx>]

At 12:49 +0200 on 13 Nov (1352810986), Razvan Cojocaru wrote:
> >>OK, my immediate end-goal is real-time logging of hypervisor events via
> >>a dom0 userspace application. These events are always about a currently
> >>running virtual machine, and said virtual machine is paused at the time.
> >>The userspace tool should be immediately notified, so no polling.
> >
> >This is very like the ioreq model, where the domain (or maybe just the
> >vcpu, I'm not sure) is paused while qemu does its thing.
> >
> >What sort of events are we talking about here?
> 
> A list of interesting registers that changed, that a page fault occured, 
> things like that, occasionally containing some small string messages 
> with extra information. Should be around 64 bytes or so.
> 
> >The right thing to do here is for the userspace tool to communicate with
> >the toolstack (by whatever means) rather the hypervisor in order to
> >control the domains.
> 
> That's what I was thinking too.
> 
> >You might also find some inspiration for this sort of model in the
> >xenpaging and memshare code.

Yes, the mem-event api that they use is pretty well suited to this -- it
sends a series of events to userspace, wih the option of pausing the
guest VCPU until userspace acknowledges the event.  ISRT the mem-access
API already allows for certain kinds of register info (CR3 writes) to be
sent on that channel.

Cheers,

Tim.

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