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

Sai Prakash Ranjan
2020-10-16T08:40:51Z

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/arm64/kvm/pmu.c
>

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

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