linux-kernel - Re: [PATCH v1 0/4] coresight: etm: Correct (virtual) contextID tracing for namespace

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Date:   Tue, 16 Nov 2021 13:52:52 +0000
From:   Suzuki K Poulose <suzuki.poulose@....com>
To:     Leo Yan <leo.yan@...aro.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Mike Leach <mike.leach@...aro.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        James Clark <james.clark@....com>, coresight@...ts.linaro.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 0/4] coresight: etm: Correct (virtual) contextID
 tracing for namespace

Hi Leo


On 31/10/2021 14:42, Leo Yan wrote:
> If a profiling program runs in a non-root PID namespace, if CoreSight
> driver enables contextID tracing, it can lead to mismatching issue
> between the context ID in hardware trace data and the allocated PID in
> the non-root namespace.
> 
> CoreSight driver has tried to address this issue for the contextID
> related interfaces under sysfs, but it misses other parts: it doesn't
> prevent user to set VMID (virtual contextID) for kernel runs in EL2 with
> VHE, and furthermore, it misses to handle the perf mode when the
> profiling tool (e.g. perf) doesn't run in root PID namespace.
> 
> For this reason, this patch series is to correct contextID tracing for
> non-root namespace.
> 
> Patch 01 is to use spinlock to protect reading virtual context ID
> comparator.
> 
> Patch 02 corrects the virtual contextID tracing for non-root PID
> namespace.
> 
> Patch 03/04 are used to fix the contextID tracing for perf mode.
> 
> I only verified this patch series on Juno board in the root PID
> namespace and confirmed the patches don't introduce any regression for
> root PID namespace.
> 

I have finished reviewing the set.

Suzuki