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 C352FC761AF for ; Thu, 30 Mar 2023 10:53:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230122AbjC3Kx4 (ORCPT ); Thu, 30 Mar 2023 06:53:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49768 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229608AbjC3Kxy (ORCPT ); Thu, 30 Mar 2023 06:53:54 -0400 Received: from mga02.intel.com (mga02.intel.com [134.134.136.20]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DD2F64C2F for ; Thu, 30 Mar 2023 03:53:53 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1680173633; x=1711709633; h=from:to:cc:subject:in-reply-to:references:date: message-id:mime-version:content-transfer-encoding; bh=/a2NUyQvjACpQ05kbhWwDQBqs0dGUOck0k692foQm/k=; b=RljzMu/RZkHzBbdI5hVRMg0edt12gI3DcLsIi3T91okiRtlfYTwiYLKu +D3y8KAUHhLum0z3UhHwQchCAJRx0gQPPCkXAAco8P2wCHmojSJk2AE15 JsIhOY9fXO1cZZ7BspJJZTA5rfUqYkdvv4gEcov6eEB3hD9J0Dk54fXoc f9nNm/c7PcdSYL4FKwoy2PpFwq7YtCb9MBZtfO17X7zaKea0ig78fEbAG VvbEVMpSJJUKqpuK0XXw66yN+tLH6TGeBoEO+nLPsVrVLy1reqIvmwxYu ASQ3HFIuBnywz39/se6g6fTtW5M1otHyMUX7UZBElAlD9NjwI5Kxsk43B w==; X-IronPort-AV: E=McAfee;i="6600,9927,10664"; a="329628463" X-IronPort-AV: E=Sophos;i="5.98,303,1673942400"; d="scan'208";a="329628463" Received: from fmsmga005.fm.intel.com ([10.253.24.32]) by orsmga101.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 30 Mar 2023 03:53:53 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10664"; a="1014392291" X-IronPort-AV: E=Sophos;i="5.98,303,1673942400"; d="scan'208";a="1014392291" Received: from unknown (HELO localhost) ([10.237.66.160]) by fmsmga005-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 30 Mar 2023 03:53:49 -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 1/2] drm: buddy_allocator: Fix buddy allocator init on 32-bit systems In-Reply-To: <20230329065532.2122295-1-davidgow@google.com> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo References: <20230329065532.2122295-1-davidgow@google.com> Date: Thu, 30 Mar 2023 13:53:47 +0300 Message-ID: <878rfe4iis.fsf@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 29 Mar 2023, David Gow wrote: > The drm buddy allocator tests were broken on 32-bit systems, as > rounddown_pow_of_two() takes a long, and the buddy allocator handles > 64-bit sizes even on 32-bit systems. > > This can be reproduced with the drm_buddy_allocator KUnit tests on i386: > ./tools/testing/kunit/kunit.py run --arch i386 \ > --kunitconfig ./drivers/gpu/drm/tests drm_buddy > > (It results in kernel BUG_ON() when too many blocks are created, due to > the block size being too small.) > > This was independently uncovered (and fixed) by Lu=C3=ADs Mendes, whose p= atch > added a new u64 variant of rounddown_pow_of_two(). This version instead > recalculates the size based on the order. > > Reported-by: Lu=C3=ADs Mendes > Link: https://lore.kernel.org/lkml/CAEzXK1oghXAB_KpKpm=3D-CviDQbNaH0qfgYT= SSjZgvvyj4U78AA@mail.gmail.com/T/ > Signed-off-by: David Gow > --- > drivers/gpu/drm/drm_buddy.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/gpu/drm/drm_buddy.c b/drivers/gpu/drm/drm_buddy.c > index 3d1f50f481cf..7098f125b54a 100644 > --- a/drivers/gpu/drm/drm_buddy.c > +++ b/drivers/gpu/drm/drm_buddy.c > @@ -146,8 +146,8 @@ int drm_buddy_init(struct drm_buddy *mm, u64 size, u6= 4 chunk_size) > unsigned int order; > u64 root_size; >=20=20 > - root_size =3D rounddown_pow_of_two(size); > - order =3D ilog2(root_size) - ilog2(chunk_size); > + order =3D ilog2(size) - ilog2(chunk_size); > + root_size =3D chunk_size << order; Just noticed near the beginning of the function there's also: if (!is_power_of_2(chunk_size)) return -EINVAL; which is also wrong for 32-bit. BR, Jani. >=20=20 > root =3D drm_block_alloc(mm, NULL, order, offset); > if (!root) --=20 Jani Nikula, Intel Open Source Graphics Center