Re: [Xen-devel] Hypervisor to dom0 communication

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Tue, 2012-11-13 at 10:49 +0000, 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.

Perhaps it would be useful to build on the vmitools (previously
xenaccess)? http://code.google.com/p/vmitools/ 

I don't know what level of support it has for trapping on certain events
but it seems like a model where the guest is stopped due to an event,
the tools are signalled and use vmi to figure out what changed etc might
be an interesting one.

In general we prefer not to put stuff in the hypervisor unless
absolutely required.

Ian.


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