From patchwork Tue Jul 15 16:20:41 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Michel Thierry X-Patchwork-Id: 4555391 Return-Path: X-Original-To: patchwork-intel-gfx@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.19.201]) by patchwork1.web.kernel.org (Postfix) with ESMTP id CA9D19F3BC for ; Tue, 15 Jul 2014 16:20:59 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id EE9F420120 for ; Tue, 15 Jul 2014 16:20:58 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) by mail.kernel.org (Postfix) with ESMTP id EDF4C20123 for ; Tue, 15 Jul 2014 16:20:57 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 7DCFB6E5BF; Tue, 15 Jul 2014 09:20:57 -0700 (PDT) X-Original-To: intel-gfx@lists.freedesktop.org Delivered-To: intel-gfx@lists.freedesktop.org Received: from mga09.intel.com (mga09.intel.com [134.134.136.24]) by gabe.freedesktop.org (Postfix) with ESMTP id 13F4C6E5BD for ; Tue, 15 Jul 2014 09:20:56 -0700 (PDT) Received: from orsmga002.jf.intel.com ([10.7.209.21]) by orsmga102.jf.intel.com with ESMTP; 15 Jul 2014 09:15:20 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.01,666,1400050800"; d="scan'208";a="573515254" Received: from michelth-linux.iwi.intel.com ([172.28.253.148]) by orsmga002.jf.intel.com with ESMTP; 15 Jul 2014 09:20:53 -0700 From: Michel Thierry To: intel-gfx@lists.freedesktop.org Date: Tue, 15 Jul 2014 17:20:41 +0100 Message-Id: <1405441251-28744-5-git-send-email-michel.thierry@intel.com> X-Mailer: git-send-email 1.9.0 In-Reply-To: <1405441251-28744-1-git-send-email-michel.thierry@intel.com> References: <1405441251-28744-1-git-send-email-michel.thierry@intel.com> Subject: [Intel-gfx] [PATCH 04/14] drm/i915/ctx: Return earlier on failure X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" X-Spam-Status: No, score=-4.2 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_MED, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Ben Widawsky As what was correctly debugged here: commit acc240d41ea1ab9c488a79219fb313b5b46265ae Author: Daniel Vetter Date: Thu Dec 5 15:42:34 2013 +0100 drm/i915: Fix use-after-free in do_switch It then becomes apparent that the default context cannot be the context being switched to for context switch because it is always bound. It follows that if the ring->last_context (from) has changed after the bind_to_gtt, it will always be the default context - this is commented in the code block. This assertion will help catch issues without our logic sooner than letting the system move long (which is possible for some time). I really want this to be a BUG(), but I also want the patch to get merged. I think the fact that none of the ERRNOs make any sense at all is just more evidence that this shouldn't be a WARN. //Cc: Ian Lister (don't have current email address) Cc: Rafael Barbalho Signed-off-by: Ben Widawsky --- drivers/gpu/drm/i915/i915_gem_context.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c index cfec178..fab74d3 100644 --- a/drivers/gpu/drm/i915/i915_gem_context.c +++ b/drivers/gpu/drm/i915/i915_gem_context.c @@ -690,6 +690,15 @@ static int do_switch_rcs(struct intel_engine_cs *ring, */ from = ring->last_context; + /* The only context which 'from' can be, if it was changed, is the default + * context. The default context cannot end up in evict everything (as + * commented above) because it is always pinned. + */ + if (WARN_ON(from == to)) { + ret = -EPERM; + goto unpin_out; + } + if (needs_pd_load) { /* Older GENs still want the load first, "PP_DCLV followed by * PP_DIR_BASE register through Load Register Immediate commands