From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.fireflyinternet.com ([87.106.93.118]:50047 "EHLO fireflyinternet.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1750845AbbEZIuV (ORCPT ); Tue, 26 May 2015 04:50:21 -0400 Date: Tue, 26 May 2015 09:49:15 +0100 From: Chris Wilson To: Daniel Vetter Cc: intel-gfx@lists.freedesktop.org, Akash Goel , stable@vger.kernel.org Subject: Re: [Intel-gfx] [PATCH v2] drm/i915: Force wmb() on using GTT io_mapping_map_wc Message-ID: <20150526084915.GD20703@nuc-i3427.alporthouse.com> References: <1432568322-20651-1-git-send-email-chris@chris-wilson.co.uk> <1432576124-20523-1-git-send-email-chris@chris-wilson.co.uk> <20150526080124.GF12971@phenom.ffwll.local> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150526080124.GF12971@phenom.ffwll.local> Sender: stable-owner@vger.kernel.org List-ID: On Tue, May 26, 2015 at 10:01:24AM +0200, Daniel Vetter wrote: > On Mon, May 25, 2015 at 06:48:44PM +0100, Chris Wilson wrote: > > Since the advent of mmap(wc), where we reused the same cache domain for > > WC and GTT paths (oh, how I regret that double-edged advice), we need to > > be extra cautious when using GTT iomap_wc internally. Since userspace maybe > > modifying through the mmap(wc) and we then modify modifying through an > > aliased WC path through the GTT, those writes may overlap and not be > > visible to the other path. Easiest to trigger appears to be write the > > batch through mmap(wc) and then attempt to perform reloc the GTT, > > corruption quickly ensues. > > > > v2: Be stricter and do a full mb() in case we are reading through one > > path and about to write through the second path. Also, apply the > > barriers on transitioning into the GTT domain as well to cover the white > > lie asychronous cases. > > > > Signed-off-by: Chris Wilson > > Cc: Akash Goel > > Cc: stable@vger.kernel.org > > There are a lot more mb() and wmb() in the gem code. I count execlist, > legacy rings, pwrite, set_domain and finish_gtt. You have more than I have... -Chris -- Chris Wilson, Intel Open Source Technology Centre