From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Vetter Subject: Re: [PATCH 1/7] drm/i915: Fix the offset issue for the stolen GEM objects Date: Thu, 9 Jan 2014 10:58:35 +0100 Message-ID: <20140109095835.GB4770@phenom.ffwll.local> References: <1389245417-10813-1-git-send-email-akash.goel@intel.com> <20140109094520.GB3245@nuc-i3427.alporthouse.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail-ea0-f173.google.com (mail-ea0-f173.google.com [209.85.215.173]) by gabe.freedesktop.org (Postfix) with ESMTP id D88C3106517 for ; Thu, 9 Jan 2014 01:57:20 -0800 (PST) Received: by mail-ea0-f173.google.com with SMTP id o10so1323282eaj.18 for ; Thu, 09 Jan 2014 01:57:20 -0800 (PST) Content-Disposition: inline In-Reply-To: <20140109094520.GB3245@nuc-i3427.alporthouse.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: intel-gfx-bounces@lists.freedesktop.org Errors-To: intel-gfx-bounces@lists.freedesktop.org To: Chris Wilson , akash.goel@intel.com, intel-gfx@lists.freedesktop.org List-Id: intel-gfx@lists.freedesktop.org On Thu, Jan 09, 2014 at 09:45:21AM +0000, Chris Wilson wrote: > On Thu, Jan 09, 2014 at 11:00:17AM +0530, akash.goel@intel.com wrote: > > From: Akash Goel > > > > The 'offset' field of the 'scatterlist' structure was wrongly > > programmed with the offset value from the base of stolen area, > > whereas this field indicates the offset from where the interested > > data starts within the PAGE pointed to by the 'page-link' field. > > As a result when a new GEM object allocated from the stolen > > area is mapped to GTT, it could lead to an overwrite of GTT entries > > as the page count calculation will go wrong, refer the function > > 'sg_page_count'. > > This statement is incorrect since my use of sg here predates > sg_page_iter. > > The stolen sg has no page_link, the meaning of offset/length here are > relative to the base of the stolen area. > > However, if you wish to rephrase the above... Actually we add offset both to sg->offset and adjust the dma_bus_addr since this has been introduced in commit 0104fdbb84d7adb0e377ed05bf75eba97b007544 Author: Chris Wilson Date: Thu Nov 15 11:32:26 2012 +0000 drm/i915: Introduce i915_gem_object_create_stolen() But only Imre's conversion to the sg_page_iter started to pay any attention to sg->offset in commit 6e995e231a90ce7c5ce2a9eae23c8e22f4388db1 Author: Imre Deak Date: Mon Feb 18 19:28:04 2013 +0200 drm/i915: use for_each_sg_page for setting up the gtt ptes So with a bit of commit message rewording and these references and cc: stable this looks good. Cheers, Daniel -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch