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=-8.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham 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 EFFB8C7113E for ; Mon, 15 Oct 2018 20:34:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B201E208E4 for ; Mon, 15 Oct 2018 20:34:14 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="g6EVVIja" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B201E208E4 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=chromium.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727013AbeJPEVE (ORCPT ); Tue, 16 Oct 2018 00:21:04 -0400 Received: from mail-pf1-f195.google.com ([209.85.210.195]:45677 "EHLO mail-pf1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725917AbeJPEVD (ORCPT ); Tue, 16 Oct 2018 00:21:03 -0400 Received: by mail-pf1-f195.google.com with SMTP id u12-v6so10238630pfn.12 for ; Mon, 15 Oct 2018 13:34:12 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=mR/nT5nCH8r3TvWFMt9H5xUCBQQEUFMwnxIrguxIQ9I=; b=g6EVVIjapTI5b5L3/qLj8K2l+oVt7Gtszlp1WrYt0FKfZjD+AXHDiXZ5AKmNMIB/Gt O9gxbNiIRGBSnuvVFzVajfbrmKviQunsrpfxnQWSIN+R6ZkrwFnJtctIthVI2rKgZANs Z6B+gB10TRvmMLyeRrLvT/9+VA7EKsHBs/svw= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=mR/nT5nCH8r3TvWFMt9H5xUCBQQEUFMwnxIrguxIQ9I=; b=RhGR1x5Toznt41CkWM8AlQsV0Wige4XgGPYRIeQOzqIT65cCY8QukMgilwyBbed3CZ 48w+dAsK+SWUG/mUM5mqurKLaalwNCFD0EwkbhaeTOvrgQhE/nGF1LkS3C3KYfj5/XWa LMqHNm10+sa9gfC3mzHbtBgYSGEIGDU5s6HYrZG33j6IOZReeARvuT0jaZCy5I5vBuN0 yYwk4Hu8QKJDZhv6Abo63yY5xT9VoIi8trPW9oRZi9HFXRFYLXAssZ/Vth6Fru+8uEs9 a1J65RIFPqF5inQPhZE32LPzm96pw2vUKJoz4CbNiQAWpmroWPorbXdUgLkXf2hk9QC4 Xkhw== X-Gm-Message-State: ABuFfohNBnRG964WuhobBY0ZJWpLBE8R8zuuqqBazUkxOZwZQBTnYk1y 08ho0Aq8+h2nERMi0L9Hpc8rxw== X-Google-Smtp-Source: ACcGV61MlM8NEJUHupS9dc3+5rBJfHhgf6100fL48kR0c7MkFoxnUI8fS8nXOMXMje/SON0BKMIQNA== X-Received: by 2002:a63:5a54:: with SMTP id k20-v6mr17566147pgm.297.1539635652175; Mon, 15 Oct 2018 13:34:12 -0700 (PDT) Received: from smtp.gmail.com ([2620:15c:202:1:fed3:9637:a13a:6c15]) by smtp.gmail.com with ESMTPSA id j2-v6sm16011954pfj.91.2018.10.15.13.34.10 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 15 Oct 2018 13:34:11 -0700 (PDT) From: Stephen Boyd To: Jani Nikula , Joonas Lahtinen , Rodrigo Vivi Cc: linux-kernel@vger.kernel.org, intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, Masahiro Yamada , Michal Marek , Andrey Ryabinin Subject: [PATCH] drm/i915: Silence build error with UBSAN Date: Mon, 15 Oct 2018 13:34:10 -0700 Message-Id: <20181015203410.155997-1-swboyd@chromium.org> X-Mailer: git-send-email 2.19.1.331.ge82ca0e54c-goog MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When I enable UBSAN and compile this driver with clang I get the following build error: drivers/gpu/drm/i915/intel_engine_cs.o: In function `intel_engine_init_execlist': drivers/gpu/drm/i915/intel_engine_cs.c:411: undefined reference to `__compiletime_assert_411' from what I can figure out, the compiler can't optimize execlists_num_ports() sufficiently enough at compile time to figure out that the 'execlists->port_mask = 1' assignment one line above the BUILD_BUG_ON_NOT_POWER_OF_2 check will make execlists_num_ports() return 2. Most likely that's because UBSAN is going to check the load inside execlists_num_ports() and that check isn't omitted so the optimizer can't optimize away the whole function. So let's just change this check to cause a build error when the maximum number of ports isn't a power of two. It looks like this is similar to what's being checked here so this might work well enough. Cc: Masahiro Yamada Cc: Michal Marek Cc: Andrey Ryabinin Signed-off-by: Stephen Boyd --- drivers/gpu/drm/i915/intel_engine_cs.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/gpu/drm/i915/intel_engine_cs.c b/drivers/gpu/drm/i915/intel_engine_cs.c index 217ed3ee1cab..bdf75628ed83 100644 --- a/drivers/gpu/drm/i915/intel_engine_cs.c +++ b/drivers/gpu/drm/i915/intel_engine_cs.c @@ -463,7 +463,7 @@ static void intel_engine_init_execlist(struct intel_engine_cs *engine) struct intel_engine_execlists * const execlists = &engine->execlists; execlists->port_mask = 1; - BUILD_BUG_ON_NOT_POWER_OF_2(execlists_num_ports(execlists)); + BUILD_BUG_ON_NOT_POWER_OF_2(EXECLIST_MAX_PORTS); GEM_BUG_ON(execlists_num_ports(execlists) > EXECLIST_MAX_PORTS); execlists->queue_priority = INT_MIN; -- Sent by a computer through tubes