Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Mon, 13 Jun 2022 16:55:28 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     Ravi Bangoria <ravi.bangoria@amd.com>
Cc:     acme@kernel.org, alexander.shishkin@linux.intel.com,
        jolsa@redhat.com, namhyung@kernel.org, songliubraving@fb.com,
        eranian@google.com, alexey.budankov@linux.intel.com,
        ak@linux.intel.com, mark.rutland@arm.com, megha.dey@intel.com,
        frederic@kernel.org, maddy@linux.ibm.com, irogers@google.com,
        kim.phillips@amd.com, linux-kernel@vger.kernel.org,
        santosh.shukla@amd.com
Subject: Re: [RFC v2] perf: Rewrite core context handling
Message-ID: <YqdP4NExuwOHdC0G@hirez.programming.kicks-ass.net>
References: <20220113134743.1292-1-ravi.bangoria@amd.com>
 <YqdLH+ZU/sf4n0pa@hirez.programming.kicks-ass.net>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <YqdLH+ZU/sf4n0pa@hirez.programming.kicks-ass.net>
Precedence: bulk

On Mon, Jun 13, 2022 at 04:35:11PM +0200, Peter Zijlstra wrote:
> @@ -12125,6 +12232,8 @@ SYSCALL_DEFINE5(perf_event_open,
>  		goto err_task;
>  	}
>  
> +	// XXX premature; what if this is allowed, but we get moved to a PMU
> +	// that doesn't have this.
>  	if (is_sampling_event(event)) {
>  		if (event->pmu->capabilities & PERF_PMU_CAP_NO_INTERRUPT) {
>  			err = -EOPNOTSUPP;

No; this really should be against the event's native PMU. If the event
can't natively sample, it can't sample when placed in another group
either.