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

Hi Leo,

On 2020-10-16 12:54, Leo Yan wrote:

On Thu, Oct 15, 2020 at 11:40:05PM -0700, Denis Nikitin wrote:

...

Hi Mathieu,

I think one of the use cases could be VMs. Is there isolation between EL1 guest kernels which we can control from perf in a system wide mode?

Sorry for suddenly jumping in.

For KVM, I think we need to implement mechanism for saving/restoring CoreSight context for every guest OS, the CPU PMUs has implemented related features [1].

Thanks, Leo

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch...

What happens to the sysfs mode of tracing? For that we would still need a config right to exclude kernel mode tracing completely.

Thanks, Sai