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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C9466C74A5B for ; Wed, 29 Mar 2023 09:39:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230359AbjC2Jjg (ORCPT ); Wed, 29 Mar 2023 05:39:36 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41638 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229759AbjC2Jje (ORCPT ); Wed, 29 Mar 2023 05:39:34 -0400 Received: from mga09.intel.com (mga09.intel.com [134.134.136.24]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 98CDF2132 for ; Wed, 29 Mar 2023 02:39:33 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1680082773; x=1711618773; h=from:to:cc:subject:in-reply-to:references:date: message-id:mime-version; bh=rmwWgXx9DUsDkyM6xIc9AQk1bMfFjEwuONpPcP5/qI4=; b=L2tBEFmCafG3bhgpX5gh7ifcpV/V+jerlBUPQTywqQKrbK3hZvqJxBWr 3Pz+8fENPXC2g7OwbSRO6oZAgKnkM8N2irU69PuMK+Xb5Qw2wJnX3r5SV 0QgF9hmaxyv7o43+eHe2SvsoCdQUoT+x+cgxvbBXVGDOPssX+475c/LAB 9Wb7aWITAZTekdfGJQX0XcnfJNUJWi9UBQ2lfJUAfdfzs4Mktb4iSyhn8 L8s43d5yBA1kgCoi1ZBrIBDpWwx65nr8/v9i02H55kG5gYiND1XIJHafO NTiB9wH939OU+FQjHE68HRmU0lj3CnbKPzp+EMsBW4I+vg8+9djqAcanF w==; X-IronPort-AV: E=McAfee;i="6600,9927,10663"; a="342423482" X-IronPort-AV: E=Sophos;i="5.98,300,1673942400"; d="scan'208";a="342423482" Received: from orsmga005.jf.intel.com ([10.7.209.41]) by orsmga102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 29 Mar 2023 02:39:32 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10663"; a="858419942" X-IronPort-AV: E=Sophos;i="5.98,300,1673942400"; d="scan'208";a="858419942" Received: from jetten-mobl1.ger.corp.intel.com (HELO localhost) ([10.252.51.146]) by orsmga005-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 29 Mar 2023 02:39:28 -0700 From: Jani Nikula To: David Gow , =?utf-8?Q?Lu=C3=ADs?= Mendes , Christian =?utf-8?Q?K=C3=B6nig?= , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Daniel Vetter , =?utf-8?Q?Ma=C3=ADra?= Canal , Arthur Grillo Cc: dri-devel@lists.freedesktop.org, David Gow , linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/2] drm: test: Fix 32-bit issue in drm_buddy_test In-Reply-To: <20230329065532.2122295-2-davidgow@google.com> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo References: <20230329065532.2122295-1-davidgow@google.com> <20230329065532.2122295-2-davidgow@google.com> Date: Wed, 29 Mar 2023 12:39:25 +0300 Message-ID: <87lejf522a.fsf@intel.com> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 29 Mar 2023, David Gow wrote: > The drm_buddy_test KUnit tests verify that returned blocks have sizes > which are powers of two using is_power_of_2(). However, is_power_of_2() > operations on a 'long', but the block size is a u64. So on systems where > long is 32-bit, this can sometimes fail even on correctly sized blocks. > > This only reproduces randomly, as the parameters passed to the buddy > allocator in this test are random. The seed 0xb2e06022 reproduced it > fine here. > > For now, just hardcode an is_power_of_2() implementation using > x & (x - 1). > > Signed-off-by: David Gow > --- > > There are actually a couple of is_power_of_2_u64() implementations > already around in: > - drivers/gpu/drm/i915/i915_utils.h > - fs/btrfs/misc.h (called is_power_of_two_u64) > > So the ideal thing would be to consolidate these in one place. > > > --- > drivers/gpu/drm/tests/drm_buddy_test.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/tests/drm_buddy_test.c b/drivers/gpu/drm/tests/drm_buddy_test.c > index f8ee714df396..09ee6f6af896 100644 > --- a/drivers/gpu/drm/tests/drm_buddy_test.c > +++ b/drivers/gpu/drm/tests/drm_buddy_test.c > @@ -89,7 +89,8 @@ static int check_block(struct kunit *test, struct drm_buddy *mm, > err = -EINVAL; > } > > - if (!is_power_of_2(block_size)) { > + /* We can't use is_power_of_2() for a u64 on 32-bit systems. */ > + if (block_size & (block_size - 1)) { Then maybe use is_power_of_2_u64() instead? BR, Jani. > kunit_err(test, "block size not power of two\n"); > err = -EINVAL; > } -- Jani Nikula, Intel Open Source Graphics Center