From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga06.intel.com (mga06.intel.com [134.134.136.31]) by dpdk.org (Postfix) with ESMTP id CFC609E3 for ; Fri, 28 Apr 2017 11:03:10 +0200 (CEST) Received: from orsmga001.jf.intel.com ([10.7.209.18]) by orsmga104.jf.intel.com with ESMTP; 28 Apr 2017 02:03:09 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.37,387,1488873600"; d="scan'208";a="1124381021" Received: from bricha3-mobl3.ger.corp.intel.com ([10.237.221.133]) by orsmga001.jf.intel.com with SMTP; 28 Apr 2017 02:03:07 -0700 Received: by (sSMTP sendmail emulation); Fri, 28 Apr 2017 10:03:07 +0100 Date: Fri, 28 Apr 2017 10:03:06 +0100 From: Bruce Richardson To: Thomas Monjalon Cc: dev@dpdk.org Message-ID: <20170428090306.GA25692@bricha3-MOBL3.ger.corp.intel.com> References: <20170428081551.28954-1-bruce.richardson@intel.com> <1797441.atIi8ZZIaG@xps> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1797441.atIi8ZZIaG@xps> Organization: Intel Research and =?iso-8859-1?Q?De=ACvel?= =?iso-8859-1?Q?opment?= Ireland Ltd. User-Agent: Mutt/1.8.0 (2017-02-23) Subject: Re: [dpdk-dev] [PATCH] eal: fix 64bit address alignment in 32-bit builds X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 28 Apr 2017 09:03:11 -0000 On Fri, Apr 28, 2017 at 10:56:56AM +0200, Thomas Monjalon wrote: > 28/04/2017 10:15, Bruce Richardson: > > On i686 builds, the uint64_t type is 64-bits in size but is aligned to > > 32-bits only. This causes mbuf fields for rearm_data to not be 16-byte > > aligned on 32-bit builds, which causes errors with some vector PMDs which > > expect the rearm data to be aligned as on 64-bit. > > > > Given that we cannot use the extra space in the data structures anyway, as > > it's already used on 64-bit builds, we can just force alignment of physical > > address structure members to 8-bytes in all cases. This has no effect on > > 64-bit systems, but fixes the updated PMDs on 32-bit. > > I agree to align on 64-bit in mbuf. > > > Fixes: f4356d7ca168 ("net/i40e: eliminate mbuf write on rearm") > > Fixes: f160666a1073 ("net/ixgbe: eliminate mbuf write on rearm") > [...] > > --- a/lib/librte_eal/common/include/rte_memory.h > > +++ b/lib/librte_eal/common/include/rte_memory.h > > -typedef uint64_t phys_addr_t; /**< Physical address definition. */ > > +/** Physical address definition. */ > > +typedef uint64_t phys_addr_t __rte_aligned(sizeof(uint64_t)); > > Why setting this constraint for everyone? > Well, it only has an effect on 32-bit builds, and unless there is a problem, I don't see why not always align them to the extra 8 bytes. If this does cause an issue, I'm happy enough to use #ifdefs, but in the absense of a confirmed problem, I'd rather keep the code clean. /Bruce