From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 429F3C48BD5 for ; Tue, 25 Jun 2019 13:30:10 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 065A2213F2 for ; Tue, 25 Jun 2019 13:30:10 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="bjB0dnGo" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 065A2213F2 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender:Content-Type: Content-Transfer-Encoding:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date:Message-ID:From: References:To:Subject:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=WSs6mfs+k63d2wVzacgYyE3Q9A3fwW1tihTQh1xj/dw=; b=bjB0dnGoHRehDM0/bqqJXVBIC gxLHp6nYXLxgY+8fcNJ4HyWmx4wGE0q7dbquT8BigCbjB7mpECl2hXKqoLAf7wpbp7gzupepxIdVz AlkTsPcuLB0gsMHMlr+J2nPfp5MBcI/R9S2auzNF+CTuXMbPcHb4qYKUMdVO/+jIrrmLiQbMn8Ypr 47+YMvYYHemS2LBFZL0e3kxWG8CkWRc1qhR7RBn5Z3CEAMA9SPiSInNUZBkn13kB92MfpPPtIcK9W tp4bsp2PgOmgDwogqfeYaT1u9KYy7mEGmMOe4eyD8PtpxjjZ/yPSQJMiDVX2qO31BAX62Z4i+GVcp ydTCHzA4Q==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1hflWQ-0001Bd-C9; Tue, 25 Jun 2019 13:30:06 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1hflWJ-0000lo-Hp for linux-arm-kernel@lists.infradead.org; Tue, 25 Jun 2019 13:30:03 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 0E1FC2B; Tue, 25 Jun 2019 06:29:59 -0700 (PDT) Received: from [10.1.196.120] (e121650-lin.cambridge.arm.com [10.1.196.120]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id DCCE93F718; Tue, 25 Jun 2019 06:29:57 -0700 (PDT) Subject: Re: [PATCH 3/7] perf: arm64: Use rseq to test userspace access to pmu counters To: Mark Rutland , will.deacon@arm.com References: <20190611125315.18736-1-raphael.gault@arm.com> <20190611125315.18736-4-raphael.gault@arm.com> <20190611143346.GB28689@kernel.org> <20190611165755.GG29008@lakrids.cambridge.arm.com> From: Raphael Gault Message-ID: Date: Tue, 25 Jun 2019 14:29:56 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <20190611165755.GG29008@lakrids.cambridge.arm.com> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190625_062959_652611_0ADF0E72 X-CRM114-Status: GOOD ( 11.40 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: peterz@infradead.org, catalin.marinas@arm.com, Arnaldo Carvalho de Melo , linux-kernel@vger.kernel.org, mingo@redhat.com, mathieu.desnoyers@efficios.com, linux-arm-kernel@lists.infradead.org Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel