linux-kernel - Re: [PATCH v2 0/4] coresight: etm: Correct PID tracing for non-root namespace

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Date:   Tue, 14 Dec 2021 10:59:58 +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>,
        coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 0/4] coresight: etm: Correct PID tracing for non-root
 namespace

On 13/12/2021 12:13, Leo Yan wrote:
> If a profiling program runs in a non-root PID namespace, if CoreSight
> driver enables PID tracing (with contextID), it can lead to mismatching
> issue between the context ID traced in hardware (from the root
> namespace) and the PIDs gathered by profiling tool (e.g. perf) in its
> non-root namespace.
> 
> CoreSight driver has tried to address this issue for the contextID
> related interfaces under sysfs, but it misses to prevent user to set
> VMID (virtual contextID) for kernel runs in EL2 with VHE; furthermore,
> it misses to handle the case when the profiling tool runs in the
> non-root PID namespace.
> 
> For this reason, this patch series is to correct contextID tracing for
> non-root namespace.  After applied this patchset, patch 02 doesn't
> permit users to access virtual contextID via sysfs nodes in the non-root
> PID namespace, patch 03 and 04 stop to trace PID packet for non-root PID
> namespace.
> 
> This patch is dependent on the patchset "pid: Introduce helper
> task_is_in_root_ns()" [1].
> 
> [1] https://lore.kernel.org/lkml/20211208083320.472503-1-leo.yan@linaro.org/
> 
> 
> Leo Yan (4):
>    coresight: etm4x: Add lock for reading virtual context ID comparator
>    coresight: etm4x: Don't use virtual contextID for non-root PID
>      namespace
>    coresight: etm4x: Don't trace PID for non-root PID namespace
>    coresight: etm3x: Don't trace PID for non-root PID namespace
> 

For the series,

Reviewed-by: Suzuki K Poulose <suzuki.poulose@....com>