Re: [PATCH 4/4] kvm: x86: export TSC offset to user-space

[Steven Rostedt]

On Fri, 2 Sep 2016 09:43:01 -0400
Stefan Hajnoczi <stefanha@xxxxxxxxx> wrote:

> Can TSC offset changes occur at runtime?
> 
> One example is vcpu hotplug where the tracing tool would need to fetch
> the new vcpu's TSC offset after tracing has already started.
> 
> Another example is if QEMU or the guest change the TSC offset while
> running.  If the tracing tool doesn't notice this then trace events will have
> incorrect timestamps.

I believe there are tracepoints for these events. They would obviously
need to be enabled for the tracer to catch them.

I would also recommend that they go into their own instance to make
sure other events do not overwrite them.

-- Steve