From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ben Widawsky Subject: Re: [PATCH] drm/i915: set ctx->initialized only after RCS Date: Thu, 9 Jan 2014 15:17:25 -0800 Message-ID: <20140109231725.GA4522@bwidawsk.net> References: <1388266309-1178-1-git-send-email-benjamin.widawsky@intel.com> <20140107071033.GB16015@phenom.ffwll.local> <20140107104718.GD8991@nuc-i3427.alporthouse.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail.bwidawsk.net (bwidawsk.net [166.78.191.112]) by gabe.freedesktop.org (Postfix) with ESMTP id 4C4BAFBA2B for ; Thu, 9 Jan 2014 15:17:41 -0800 (PST) Content-Disposition: inline In-Reply-To: <20140107104718.GD8991@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 , Daniel Vetter , Ben Widawsky , Intel GFX List-Id: intel-gfx@lists.freedesktop.org On Tue, Jan 07, 2014 at 10:47:18AM +0000, Chris Wilson wrote: > On Tue, Jan 07, 2014 at 08:10:33AM +0100, Daniel Vetter wrote: > > On Sat, Dec 28, 2013 at 01:31:49PM -0800, Ben Widawsky wrote: > > > The initialized flag is used to specify a context has been initialized > > > and it's context is safe to load, ie. the 3d state is setup properly. > > > With full PPGTT, we emit the address space loads during context switch > > > and this currently marks a context as initialized. With full PPGTT > > > patches, if a client first emits a batch to !RCS, then later, RCS, the > > > code will mistake the context as initialized and try to reload an > > > uninitialized context. > > > > > > 1. context 1 blit // context initialized > > > 2. context 2 // saves context 1 random state > > > 3. context 1 render // loads random state from step 2 > > > > > > It is really easy to hit this with a planned upcoming patch which makes > > > default context reuse possible. > > > > > > NOTE: This should only effect full PPGTT branches, ie. current > > > drm-intel-nightly. > > > > > > Thanks to Chris for helping me track this down. > > > > > > Cc: Chris Wilson > > > Signed-off-by: Ben Widawsky > > > > Do we have a testcase for this or a bug report? > > Odd, since QA should have hit this... > -Chris I was only able to hit it on one machine. The test case was 'startx.' I think getting it to fail is somewhat dependent upon how the backing pages for the context are initialized (at least, that is my theory). -- Ben Widawsky, Intel Open Source Technology Center