From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934072AbcBQKrw (ORCPT ); Wed, 17 Feb 2016 05:47:52 -0500 Received: from mail-bl2on0081.outbound.protection.outlook.com ([65.55.169.81]:61536 "EHLO na01-bl2-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S934008AbcBQKru (ORCPT ); Wed, 17 Feb 2016 05:47:50 -0500 Authentication-Results: arm.com; dkim=none (message not signed) header.d=none;arm.com; dmarc=none action=none header.from=caviumnetworks.com; Date: Wed, 17 Feb 2016 11:47:35 +0100 From: Jan Glauber To: Will Deacon CC: Mark Rutland , , Subject: Re: [PATCH v3 5/5] arm64/perf: Extend event mask for ARMv8.1 Message-ID: <20160217104735.GA3318@hardcore> References: <20160215200404.GX6298@arm.com> <20160216080015.GA3490@hardcore> <20160216151252.GG14509@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20160216151252.GG14509@arm.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-Originating-IP: [46.223.157.133] X-ClientProxiedBy: DB5PR03CA0025.eurprd03.prod.outlook.com (25.162.150.35) To BLUPR0701MB756.namprd07.prod.outlook.com (10.141.252.22) X-Microsoft-Exchange-Diagnostics: 1;BLUPR0701MB756;2:TfplKmS2s/XlWX1BU2PXaDbhqnIQthaXA7iBVjxu6VjMlHCIdkm9XCTHspejPoYbdBVL9jfGk5Ty2I3sGlxRu2/fY2cOQ1dJD/RLfj7a7JEZye73dge8eLHyo+TKRlkU6lU1KsuUqxQzO7MXN6E4ew==;3:+UdB/Wah0j7QCodanF7nJmfOUAYXTjmWVq6roMYrojGztWDs4Q15KR1JJ1XM6jw2LEHl4KSmTBYnBddAzvGxnFnlSnByMn0D5GbAdsrPxaQ7g+Q+hWq5qlNoTWUBGcUj;25:xrt8Glx+44OxE543NcWo80rmV6EdzgyoUwRmLVYdrGKEi2QTxY4lY3dLpIu96B2ocQQ0gHFJMmtoLAqgG8XDKHGjMzXsgKfBS4u0Lgf052IYDqkiRAOXbboNOoqM0QmAipplRZBiBb1blDNxytZCBwQoyj2mp24og1mDwffbr41VqlLvqngISz/Vwsd1HLXP5mNO/lBbX96XWt1TzZFuHMm2xuq31K63X9k0VjrTYLUvEJ2rCYTuZ5AxRhsxKCdodOBls6Vrl/+y6Wwk87x7wgdgcyFnq7OiTVmWE/tdphQxnvYc/WKV4XE+Cqb6heyQ X-Microsoft-Antispam: UriScan:;BCL:0;PCL:0;RULEID:;SRVR:BLUPR0701MB756; 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/* ARMv8.1 extended events */ > > > > + else > > > > + cpu_pmu->event_mask = ARMV8_EVTYPE_EVENT; > > > > > > ... although can't we just update ARMV8_EVTYPE_EVENT to be 0xffff now? > > > AFAICT, that just eats into bits that used to be RES0, so we shouldn't > > > see any problems. That should make your patch *much* simpler! > > > > That would of course be easier, but I just can't assess the implications. > > > > Probably I'm missing something but to me it looks like the event mask is the > > only verification we do for the user-space selectable events. Is it safe for > > implementations that only support 0x3ff events to allow access to the > > whole 0xffff range? What memory would be accessed for non-existing > > events? > > Which memory? The worst-case is that we end up writing to some bits in > a register (e.g. PMXEVTYPER) that are RES0 in ARMv8 afaict. OK, I see. Than I'm happy to drop 99% of that patch and just increase the mask. Jan > Will