From: Peter Zijlstra <peterz@infradead.org>
To: Raphael Gault <raphael.gault@arm.com>
Cc: linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, mingo@redhat.com,
catalin.marinas@arm.com, will.deacon@arm.com, acme@kernel.org,
mark.rutland@arm.com
Subject: Re: [RFC 4/7] arm64: pmu: Add function implementation to update event index in userpage.
Date: Wed, 29 May 2019 11:46:59 +0200 [thread overview]
Message-ID: <20190529094659.GK2623@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20190528150320.25953-5-raphael.gault@arm.com>
On Tue, May 28, 2019 at 04:03:17PM +0100, Raphael Gault wrote:
> +static int armv8pmu_access_event_idx(struct perf_event *event)
> +{
> + if (!(event->hw.flags & ARMPMU_EL0_RD_CNTR))
> + return 0;
> +
> + /*
> + * We remap the cycle counter index to 32 to
> + * match the offset applied to the rest of
> + * the counter indeces.
> + */
> + if (event->hw.idx == ARMV8_IDX_CYCLE_COUNTER)
> + return 32;
> +
> + return event->hw.idx;
Is there a guarantee event->hw.idx is never 0? Or should you, just like
x86, use +1 here?
> +}
next prev parent reply other threads:[~2019-05-29 9:47 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-28 15:03 [RFC V2 0/7] arm64: Enable access to pmu registers by user-space Raphael Gault
2019-05-28 15:03 ` [RFC 1/7] perf: arm64: Compile tests unconditionally Raphael Gault
2019-05-28 15:19 ` Arnaldo Carvalho de Melo
2019-05-28 16:16 ` Mark Rutland
2019-05-28 15:03 ` [RFC 2/7] perf: arm64: Add test to check userspace access to hardware counters Raphael Gault
2019-05-28 15:03 ` [RFC 3/7] perf: arm64: Use rseq to test userspace access to pmu counters Raphael Gault
2019-05-28 15:03 ` [RFC 4/7] arm64: pmu: Add function implementation to update event index in userpage Raphael Gault
2019-05-29 9:46 ` Peter Zijlstra [this message]
2019-05-29 10:46 ` Raphael Gault
2019-05-29 10:50 ` Robin Murphy
2019-05-29 12:25 ` Raphael Gault
2019-05-29 12:32 ` Peter Zijlstra
2019-05-29 12:39 ` Raphael Gault
2019-05-28 15:03 ` [RFC 5/7] arm64: pmu: Add hook to handle pmu-related undefined instructions Raphael Gault
2019-05-29 9:45 ` Peter Zijlstra
2019-05-28 15:03 ` [RFC 6/7] arm64: perf: Enable pmu counter direct access for perf event on armv8 Raphael Gault
2019-05-28 15:03 ` [RFC 7/7] Documentation: arm64: Document PMU counters access from userspace Raphael Gault
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