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=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 2C9E7C2D0CE for ; Tue, 21 Jan 2020 10:22:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0B5C724125 for ; Tue, 21 Jan 2020 10:22:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729624AbgAUKWJ (ORCPT ); Tue, 21 Jan 2020 05:22:09 -0500 Received: from metis.ext.pengutronix.de ([85.220.165.71]:47001 "EHLO metis.ext.pengutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728512AbgAUKWF (ORCPT ); Tue, 21 Jan 2020 05:22:05 -0500 Received: from kresse.hi.pengutronix.de ([2001:67c:670:100:1d::2a]) by metis.ext.pengutronix.de with esmtp (Exim 4.92) (envelope-from ) id 1itqfZ-0004jX-IB; Tue, 21 Jan 2020 11:22:01 +0100 Message-ID: <8d86fcb526ee14c7e6c80a787db645192c2c7c33.camel@pengutronix.de> Subject: Re: [PATCH v2 13/24] drm/etnaviv: reject timeouts with tv_nsec >= NSEC_PER_SEC From: Lucas Stach To: Arnd Bergmann Cc: Guido =?ISO-8859-1?Q?G=FCnther?= , Philipp Zabel , y2038 Mailman List , The etnaviv authors , dri-devel , "linux-kernel@vger.kernel.org" , David Airlie , Christian Gmeiner , Daniel Vetter , Russell King , Emil Velikov , Sam Ravnborg Date: Tue, 21 Jan 2020 11:21:56 +0100 In-Reply-To: References: <20191213204936.3643476-1-arnd@arndb.de> <20191213205417.3871055-4-arnd@arndb.de> <20200117154726.GA328525@bogon.m.sigxcpu.org> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.30.5-1.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-SA-Exim-Connect-IP: 2001:67c:670:100:1d::2a X-SA-Exim-Mail-From: l.stach@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-kernel@vger.kernel.org Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mo, 2020-01-20 at 19:47 +0100, Arnd Bergmann wrote: > On Mon, Jan 20, 2020 at 6:48 PM Lucas Stach wrote: > > On Fr, 2020-01-17 at 16:47 +0100, Guido Günther wrote: > > > This breaks rendering here on arm64/gc7000 due to > > > > > > ioctl(6, DRM_IOCTL_ETNAVIV_GEM_CPU_PREP or DRM_IOCTL_MSM_GEM_CPU_PREP, 0xfffff7888680) = -1 EINVAL (Invalid argument) > > > ioctl(6, DRM_IOCTL_ETNAVIV_GEM_CPU_FINI or DRM_IOCTL_QXL_CLIENTCAP, 0xfffff78885e0) = 0 > > > ioctl(6, DRM_IOCTL_ETNAVIV_GEM_CPU_PREP or DRM_IOCTL_MSM_GEM_CPU_PREP, 0xfffff7888680) = -1 EINVAL (Invalid argument) > > > ioctl(6, DRM_IOCTL_ETNAVIV_GEM_CPU_FINI or DRM_IOCTL_QXL_CLIENTCAP, 0xfffff78885e0) = 0 > > > ioctl(6, DRM_IOCTL_ETNAVIV_GEM_CPU_PREP or DRM_IOCTL_MSM_GEM_CPU_PREP, 0xfffff7888680) = -1 EINVAL (Invalid argument) > > > ioctl(6, DRM_IOCTL_ETNAVIV_GEM_CPU_FINI or DRM_IOCTL_QXL_CLIENTCAP, 0xfffff78885e0) = 0 > > > > > > This is due to > > > > > > get_abs_timeout(&req.timeout, 5000000000); > > > > > > in etna_bo_cpu_prep which can exceed NSEC_PER_SEC. > > > > > > Should i send a patch to revert that change since it breaks existing userspace? > > > > No need to revert. This patch has not been applied to the etnaviv tree > > yet, I guess it's just in one of Arnds branches feeding into -next. > > > > That part of userspace is pretty dumb, as it misses to renormalize > > tv_nsec when it overflows the second boundary. So if what I see is > > correct it should be enough to allow 2 * NSEC_PER_SEC, which should > > both reject broken large timeout and keep existing userspace working. > > Ah, so it's never more than 2 billion nanoseconds in known user space? > I can definitely change my patch (actually add one on top) to allow that > and handle it as before, or alternatively accept any 64-bit nanosecond value > as arm64 already did, but make it less inefficient to handle. So the broken userspace code looks like this: 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); } Which means it _tries_ to do the right thing by putting the billion part into the tv_sec member and only the remaining ns part is added to tv_nsec, but then it fails to propagate a tv_nsec overflow over NSEC_PER_SEC into tv_sec. Which means the tv_nsec should never be more than 2 * NSEC_PER_SEC in known userspace. I would prefer if we could make the interface as strict as possible (i.e. no arbitrary large numbers in tv_nsec), while keeping this specific corner case working. Regards, Lucas