linux-kernel - Re: [PATCH v1 2/4] coresight: etm4x: Don't use virtual contextID for non-root PID namespace

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Date:   Thu, 4 Nov 2021 23:24:26 +0800
From:   Leo Yan <leo.yan@...aro.org>
To:     Suzuki K Poulose <suzuki.poulose@....com>
Cc:     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 2/4] coresight: etm4x: Don't use virtual contextID for
 non-root PID namespace

On Thu, Nov 04, 2021 at 03:07:45PM +0000, Suzuki Kuruppassery Poulose wrote:

[...]

> > @@ -2111,6 +2111,13 @@ static ssize_t vmid_val_show(struct device *dev,
> >   	struct etmv4_drvdata *drvdata = dev_get_drvdata(dev->parent);
> >   	struct etmv4_config *config = &drvdata->config;
> > +	/*
> > +	 * Don't use virtual contextID tracing if coming from a PID namespace.
> > +	 * See comment in ctxid_pid_store().
> > +	 */
> > +	if (task_active_pid_ns(current) != &init_pid_ns)
> > +		return -EINVAL;
> > +
> >   	spin_lock(&drvdata->spinlock);
> >   	val = (unsigned long)config->vmid_val[config->vmid_idx];
> >   	spin_unlock(&drvdata->spinlock);
> > @@ -2125,6 +2132,13 @@ static ssize_t vmid_val_store(struct device *dev,
> >   	struct etmv4_drvdata *drvdata = dev_get_drvdata(dev->parent);
> >   	struct etmv4_config *config = &drvdata->config;
> > +	/*
> > +	 * Don't use virtual contextID tracing if coming from a PID namespace.
> > +	 * See comment in ctxid_pid_store().
> > +	 */
> > +	if (task_active_pid_ns(current) != &init_pid_ns)
> 
> Please could we add a helper function to make this obvious ?
> 
> e.g: task_is_in_root_ns(task) ?

Yeah, I will use a separate patch set to add this helper function and
polish relevant codes in the kernel.  Thanks for suggestion.

Leo