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

[Suzuki Poulose]

On 10/16/20 2:14 PM, Leo Yan wrote:
> 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?

I wouldn't even think of virtualizing the components without sysreg
access. So let us not worry about it :-)

Cheers
Suzuki