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=-2.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no 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 21AB9C2D0DB for ; Wed, 22 Jan 2020 10:36:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EBFF124655 for ; Wed, 22 Jan 2020 10:36:24 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=armlinux.org.uk header.i=@armlinux.org.uk header.b="Jv2YkmeB" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729325AbgAVKgY (ORCPT ); Wed, 22 Jan 2020 05:36:24 -0500 Received: from pandora.armlinux.org.uk ([78.32.30.218]:37994 "EHLO pandora.armlinux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729110AbgAVKgX (ORCPT ); Wed, 22 Jan 2020 05:36:23 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=armlinux.org.uk; s=pandora-2019; h=Sender:In-Reply-To: Content-Transfer-Encoding:Content-Type:MIME-Version:References:Message-ID: Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=qV0nPj5tEVoFXSxisYrwpsdGo4tcFtq0OnTwiKfamQ0=; b=Jv2YkmeB9uF1EaComQ4haMGNK e8aqhElhaSEvbl/SpMYwdeF81r3tuwpyZBiSL5Zr2VV9gUB6me6afaJs7SyDSJNxDUxXNs553q2WE f+qrqarjg49fIIFAPJ1XO1of1VdOvlq+QfbqP4mqgcm+JrOcJoqd1hutQ3Ev0npvuVP5eHhQXrRk9 LJU/k6FU7mWBxJFLzFg455xzOFjE9Cbr4b0eDm9jD/LrTltZ6TlS0LLlQ+/51rMIurF8XHNhy5oeH ztr1i7j0NOHjHI7NEk/l3C7sYhkUaKIeYTKf2hnK1llgI4uxGlrgOavs5COWjWqkx0xKPh6t0W2ud B8ELuE/zQ==; Received: from shell.armlinux.org.uk ([2002:4e20:1eda:1:5054:ff:fe00:4ec]:37606) by pandora.armlinux.org.uk with esmtpsa (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.90_1) (envelope-from ) id 1iuDMc-0002KF-MP; Wed, 22 Jan 2020 10:35:58 +0000 Received: from linux by shell.armlinux.org.uk with local (Exim 4.92) (envelope-from ) id 1iuDMX-0004l8-9Y; Wed, 22 Jan 2020 10:35:53 +0000 Date: Wed, 22 Jan 2020 10:35:53 +0000 From: Russell King - ARM Linux admin To: Guido =?iso-8859-1?Q?G=FCnther?= Cc: Arnd Bergmann , Lucas Stach , Christian Gmeiner , David Airlie , Daniel Vetter , Philipp Zabel , Sam Ravnborg , Rob Herring , Emil Velikov , The etnaviv authors , dri-devel , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH] drm/etnaviv: only reject timeouts with tv_nsec >= 2 seconds Message-ID: <20200122103553.GN25745@shell.armlinux.org.uk> References: <20200121114553.2667556-1-arnd@arndb.de> <20200121125546.GA71415@bogon.m.sigxcpu.org> <1971902c68ff805ee0b4a66f558afe06e6edf0c5.camel@pengutronix.de> <20200122103034.GA67385@bogon.m.sigxcpu.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20200122103034.GA67385@bogon.m.sigxcpu.org> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jan 22, 2020 at 11:30:34AM +0100, Guido Günther wrote: > Hi, > On Tue, Jan 21, 2020 at 08:05:27PM +0100, Arnd Bergmann wrote: > > On Tue, Jan 21, 2020 at 5:10 PM Lucas Stach wrote: > > > > > > Hi Guido, > > > > > > On Di, 2020-01-21 at 13:55 +0100, Guido Günther wrote: > > > > Hi, > > > > On Tue, Jan 21, 2020 at 12:45:25PM +0100, Arnd Bergmann wrote: > > > > > As Guido Günther reported, get_abs_timeout() in the etnaviv user space > > > > > sometimes passes timeouts with nanosecond values larger than 1000000000, > > > > > which gets rejected after my first patch. > > > > > > > > > > To avoid breaking this, while also not allowing completely arbitrary > > > > > values, set the limit to 1999999999 and use set_normalized_timespec64() > > > > > to get the correct format before comparing it. > > > > > > > > I'm seeing values up to 5 seconds so I need > > > > > > > > if (args->timeout.tv_nsec > (5 * NSEC_PER_SEC)) > > > > > > > > to unbreak rendering. Which seems to match what mesa's get_abs_timeout() > > > > does and how it's invoked. > > > > > > I have not tested this myself yet, only looked at the code. From the > > > code I quoted earlier, I don't see how we end up with 5 * NSEC_PER_SEC > > > in the tv_nsec member, even if the timeout passed to get_abs_timeout() > > > is 5 seconds. > > > > I can think of two different ways you'd end up with around five seconds here: > > > > a) you have a completely arbitrary 32-bit number through truncation, > > which is up to 4.2 seconds > > b) you have the same kind of 32-bit number, but add up to another 999999999 > > nanoseconds, so you get up to 5.2 seconds in the 64-bit field. > > I've dumped out some values tv_nsec values with current mesa git on arm64: > > [ 33.699652] etnaviv_ioctl_gem_cpu_prep: 4990449401 > [ 33.813081] etnaviv_ioctl_gem_cpu_prep: 5103872445 > [ 33.822936] etnaviv_ioctl_gem_cpu_prep: 5113731286 > [ 33.840963] etnaviv_ioctl_gem_cpu_prep: 5131762726 > [ 33.854120] etnaviv_ioctl_gem_cpu_prep: 5144920127 > [ 33.861426] etnaviv_ioctl_gem_cpu_prep: 5152227527 > [ 33.872666] etnaviv_ioctl_gem_cpu_prep: 5163466968 > [ 33.879485] etnaviv_ioctl_gem_cpu_prep: 5170286808 > > The problem is that in mesa/libdrm > > static inline void get_abs_timeout(struct drm_etnaviv_timespec *tv, uint64_t ns) > { > struct timespec t; > uint32_t s = ns / 1000000000; > clock_gettime(CLOCK_MONOTONIC, &t); > tv->tv_sec = t.tv_sec + s; > tv->tv_nsec = t.tv_nsec + ns - (s * 1000000000); > ^^^^^^^^^^^^^^^ > this overflows (since `s` is `uint_32t` and hence we substract a way > too small value with ns = 5000000000 which mesa uses in > etna_bo_cpu_prep. > } > > So with current mesa/libdrm (which needs to be fixed) we'd have a maximum > > t.tv_nsec + ns - (s_max * 1000000000) > > 999999999 + 5000000000 - 705032704 = 5294967295 > > Does that make sense? If so that'd be the possible upper bound for the > kernel. Note that this only applies to etnaviv_ioctl_gem_cpu_prep. While > etnaviv_ioctl_wait_fence and etnaviv_ioctl_gem_wait are affected too > i've not yet seen user space passing in larger values. Except the fact that the calculation being done above is buggy. Not only do we end up with tv_sec incremented by 5 seconds, but we also end up with tv_nsec containing around 5 seconds in nanoseconds, which means we end up with about a 10 second timeout. I think it would probably be better for the kernel to print a warning once when noticing over-large nsec values, suggesting a userspace upgrade is in order, but continue the existing behaviour. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up According to speedtest.net: 11.9Mbps down 500kbps up