Re: [PATCH] coresight: etm4x: Add config to exclude kernel mode tracing

Leo Yan
2020-10-16T13:14:26Z

On Fri, Oct 16, 2020 at 12:38:47PM +0100, Suzuki Kuruppassery Poulose wrote:

[...]

> > > What happens to the sysfs mode of tracing? For that we would still
> > > need a config right to exclude kernel mode tracing completely.
> >
> > IIUC, sysfs mode and perf mode both can apply the same approach, the
> > guest OS runs a thread context for the host, so when a guest OS is
> > switched in or out, the hypervisor can save/restore the context for
> > the guest OS; thus every guest OS will have its dedicated context and
> > trace data ideally.
>
> I don't think Guest Context is something we can support as mentioned
> above, at least for systems without sysreg access for ETMs (and virtualizing
> ETRs is a different story !)

Thanks for sharing thoughts, Suzuki.

I missed the device virtulisation. Here should virtualize all devices
(includes CoreSight ETM/funnel/ETR/ETF)? Or only need to virtualize
ETRs?

Obviously, this is a difficult task :)

Thanks,
Leo