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From: Raphael Gault <raphael.gault@arm.com>
To: Mark Rutland <mark.rutland@arm.com>, will.deacon@arm.com
Cc: peterz@infradead.org, catalin.marinas@arm.com,
	Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>,
	linux-kernel@vger.kernel.org, mingo@redhat.com,
	mathieu.desnoyers@efficios.com,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 3/7] perf: arm64: Use rseq to test userspace access to pmu counters
Date: Tue, 25 Jun 2019 14:29:56 +0100	[thread overview]
Message-ID: <ff5897eb-ae6c-482f-148b-947a661fde4f@arm.com> (raw)
In-Reply-To: <20190611165755.GG29008@lakrids.cambridge.arm.com>

Hi Mark, Hi Will,

Now that we have a better idea what enabling this feature for 
heterogeneous systems would look like (both with or without using 
rseqs), it might be worth discussing if this is in fact a desirable 
thing in term of performance-complexity trade off.

Indeed, while not as scary as first thought, maybe the rseq method would 
still dissuade users from using this feature. It is also worth noting 
that if we only enable this feature on homogeneous system, the `mrs` 
hook/emulation would not be necessary.
If because of the complexity of the setup we need to consider whether we 
want to upstream this and have to maintain it afterward.

Thanks,

-- 
Raphael Gault

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  parent reply	other threads:[~2019-06-25 13:30 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-11 12:53 [PATCH 0/7] arm64: Enable access to pmu registers by user-space Raphael Gault
2019-06-11 12:53 ` [PATCH 1/7] perf: arm64: Compile tests unconditionally Raphael Gault
2019-06-11 14:09   ` Mark Rutland
2019-06-11 14:23     ` Arnaldo Carvalho de Melo
2019-06-11 17:01       ` Mark Rutland
2019-06-11 12:53 ` [PATCH 2/7] perf: arm64: Add test to check userspace access to hardware counters Raphael Gault
2019-06-11 12:53 ` [PATCH 3/7] perf: arm64: Use rseq to test userspace access to pmu counters Raphael Gault
2019-06-11 14:33   ` Arnaldo Carvalho de Melo
2019-06-11 16:57     ` Mark Rutland
2019-06-11 19:33       ` Mathieu Desnoyers
2019-06-13  7:10         ` Raphael Gault
2019-06-13  8:27           ` Mathieu Desnoyers
2019-06-13 11:02         ` Raphael Gault
2019-06-25 13:20         ` Raphael Gault
2019-06-25 13:29       ` Raphael Gault [this message]
2019-06-25 13:41         ` Will Deacon
2019-06-11 12:53 ` [PATCH 4/7] arm64: pmu: Add function implementation to update event index in userpage Raphael Gault
2019-06-11 12:53 ` [PATCH 5/7] arm64: pmu: Add hook to handle pmu-related undefined instructions Raphael Gault
2019-06-11 12:53 ` [PATCH 6/7] arm64: perf: Enable pmu counter direct access for perf event on armv8 Raphael Gault
2019-06-11 12:53 ` [PATCH 7/7] Documentation: arm64: Document PMU counters access from userspace Raphael Gault

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