From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from dpdk.org (dpdk.org [92.243.14.124]) by inbox.dpdk.org (Postfix) with ESMTP id B0AFEA0350; Mon, 29 Jun 2020 18:15:47 +0200 (CEST) Received: from [92.243.14.124] (localhost [127.0.0.1]) by dpdk.org (Postfix) with ESMTP id 048361BF6C; Mon, 29 Jun 2020 18:15:47 +0200 (CEST) Received: from mga04.intel.com (mga04.intel.com [192.55.52.120]) by dpdk.org (Postfix) with ESMTP id 69BF81BEDE for ; Mon, 29 Jun 2020 18:15:45 +0200 (CEST) IronPort-SDR: 4SPmNjwTqOv+koVqjeiPA8whufOCP6hEENB2IT179jRc3GB5uHbUhdoE7ikHXvU0//AcYu1gCZ msPA10XFfo/g== X-IronPort-AV: E=McAfee;i="6000,8403,9666"; a="143474275" X-IronPort-AV: E=Sophos;i="5.75,295,1589266800"; d="scan'208";a="143474275" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga004.jf.intel.com ([10.7.209.38]) by fmsmga104.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 29 Jun 2020 09:15:44 -0700 IronPort-SDR: mkeLFwH0RttUJduZIh8L9ROwtMTtLkyGDeK/AXj1DaxnlzaW7I3pD8y7DF6tpXrf6QStSB7R4B zHITxTzIJoRg== X-IronPort-AV: E=Sophos;i="5.75,295,1589266800"; d="scan'208";a="424867117" Received: from bricha3-mobl.ger.corp.intel.com ([10.251.82.47]) by orsmga004-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-SHA; 29 Jun 2020 09:15:42 -0700 Date: Mon, 29 Jun 2020 17:15:38 +0100 From: Bruce Richardson To: Stephen Hemminger Cc: dev@dpdk.org Message-ID: <20200629161538.GE572@bricha3-MOBL.ger.corp.intel.com> References: <20200626145957.722089-1-bruce.richardson@intel.com> <20200626100542.1c87c2c9@hermes.lan> <20200629091158.GA572@bricha3-MOBL.ger.corp.intel.com> <20200629091910.GB572@bricha3-MOBL.ger.corp.intel.com> <20200629084146.6951685c@hermes.lan> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200629084146.6951685c@hermes.lan> Subject: Re: [dpdk-dev] [PATCH] eal: don't use default library path for static binaries 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: , Errors-To: dev-bounces@dpdk.org Sender: "dev" On Mon, Jun 29, 2020 at 08:41:46AM -0700, Stephen Hemminger wrote: > On Mon, 29 Jun 2020 10:19:10 +0100 > Bruce Richardson wrote: > > > On Mon, Jun 29, 2020 at 10:11:58AM +0100, Bruce Richardson wrote: > > > On Fri, Jun 26, 2020 at 10:05:42AM -0700, Stephen Hemminger wrote: > > > > On Fri, 26 Jun 2020 15:59:57 +0100 > > > > Bruce Richardson wrote: > > > > > > > > > When using statically linked DPDK binaries, the EAL checks the default PMD > > > > > path and tries to load any drivers there, despite the fact that all drivers > > > > > are normally linked into the binary. This behaviour can cause issues if > > > > > the PMD path and lib dir is configured to a non-standard location which is > > > > > not in the ld.so.conf paths, e.g. a build with prefix set to a home > > > > > directory location. In a case such as this, EAL will try and > > > > > (unnecessarily) load the .so driver files but that load will fail as their > > > > > dependent libraries, such as ethdev, for example, will not be found. > > > > > > > > > > Because of this, it is better if statically linked DPDK apps do not load > > > > > drivers from the standard paths automatically. The user can always have > > > > > this behaviour by explicitly specifying the path using -d flag, if so > > > > > desired. > > > > > > > > > > Not loading the libraries automatically can also prevent potential issues > > > > > with a user building and running a statically-linked DPDK binary based off > > > > > a private copy of DPDK, while there exists on the same machine a > > > > > system-wide installation of DPDK in the default locations. Without this > > > > > change, the system-installed drivers will be loaded to the binary alongside > > > > > the statically-linked drivers, which is not what the user would have > > > > > intended. > > > > > > > > > > To detect whether we are in a statically or dynamically linked binary, we > > > > > can have EAL try to get a dlopen handle to its own shared library, by > > > > > calling dlopen with the RTLD_NOLOAD flag. This will return NULL if there is > > > > > no such shared lib loaded i.e. the code is executing from a static library, > > > > > or a handle to the lib if it is loaded. > > > > > > > > > > Signed-off-by: Bruce Richardson > > > > > > > > But what if the majority of the DPDK is statically linked but the > > > > application wants also load a dynamically linked driver? > > > > > > > They use the -d flag as now. The only change here is that we don't > > > *automatically* (and silently) attempt to load all drivers from a system > > > location when you have a static binary. > > > > I'd also make a couple of additional points: > > 1. If you have a static app and you have extra drivers in your EAL_PMD_PATH > > directory you have no way of preventing the loading of them. > > > > 2. Since all DPDK apps try to load all files in that directory, all one has > > to do is put a non-loadable file into the DPDK PMD directory and suddenly > > all DPDK apps on the system will fail to run. [Patchset > > http://patches.dpdk.org/project/dpdk/list/?series=10553 will also help > > here] > > > > 3. Since this is a behaviour change, perhaps it needs to be deferred to > > 20.11? Ideally I think we should fix this now, because I think the current > > behaviour doesn't make sense and causes more problems than it solves, but > > if it needs to be deferred, so be it. > > > Thanks, just trying to poke the corners of this change. > Please make sure the documentation and web site match the behavior. > > Acked-by: Stephen Hemminger This appears to be a gap, since I looked through the docs and couldn't find any reference to this behaviour at all. However, I may well have missed something so please flag if so. Regards, /Bruce