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

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Message-ID: <20201016072401.GC4646@leoy-ThinkPad-X240s>
Date:   Fri, 16 Oct 2020 15:24:01 +0800
From:   Leo Yan <leo.yan@...aro.org>
To:     Denis Nikitin <denik@...omium.org>
Cc:     Mathieu Poirier <mathieu.poirier@...aro.org>,
        Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>,
        linux-arm-msm@...r.kernel.org, coresight@...ts.linaro.org,
        linux-kernel@...r.kernel.org, Stephen Boyd <swboyd@...omium.org>,
        linux-arm-kernel@...ts.infradead.org,
        Mike Leach <mike.leach@...aro.org>
Subject: Re: [PATCH] coresight: etm4x: Add config to exclude kernel mode
 tracing

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