From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga11.intel.com (mga11.intel.com [192.55.52.93]) by dpdk.org (Postfix) with ESMTP id D0FBB5581 for ; Thu, 5 May 2016 11:42:55 +0200 (CEST) Received: from orsmga003.jf.intel.com ([10.7.209.27]) by fmsmga102.fm.intel.com with ESMTP; 05 May 2016 02:42:55 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.24,581,1455004800"; d="scan'208";a="799410193" Received: from bricha3-mobl3.ger.corp.intel.com ([10.237.220.75]) by orsmga003.jf.intel.com with SMTP; 05 May 2016 02:42:52 -0700 Received: by (sSMTP sendmail emulation); Thu, 05 May 2016 10:42:51 +0025 Date: Thu, 5 May 2016 10:42:51 +0100 From: Bruce Richardson To: Thomas Monjalon Cc: Neil Horman , dev@dpdk.org, David Marchand , Stephen Hemminger , Panu Matilainen Message-ID: <20160505094251.GA11320@bricha3-MOBL3> References: <1461692391-30093-1-git-send-email-nhorman@tuxdriver.com> <20160504114305.GA27687@hmsreliant.think-freely.org> <2684085.G5NnXQEQ33@xps13> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2684085.G5NnXQEQ33@xps13> Organization: Intel Shannon Ltd. User-Agent: Mutt/1.5.23 (2014-03-12) Subject: Re: [dpdk-dev] [RFC PATCH 0/4]: Implement module information export X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 05 May 2016 09:42:56 -0000 On Wed, May 04, 2016 at 11:16:42PM +0200, Thomas Monjalon wrote: > This discussion requires more opinions. > Please everybody, READ and COMMENT. Thanks > > If it is not enough visible, a new thread could be started later. > > 2016-05-04 07:43, Neil Horman: > > On Wed, May 04, 2016 at 10:24:18AM +0200, David Marchand wrote: > > > On Tue, May 3, 2016 at 1:57 PM, Neil Horman wrote: > > > >> This approach has a few pros and cons: > > > >> > > > >> pros: > > > >> 1) Its simple, and doesn't require extra infrastructure to implement. E.g. we > > > >> don't need a new tool to extract driver information and emit the C code to build > > > >> the binary data for the special section, nor do we need a custom linker script > > > >> to link said special section in place > > > >> > > > >> 2) Its stable. Because the marker symbols are explicitly exported, this > > > >> approach is resilient against stripping. > > It is a good point. We need something resilient against stripping. > > > > >> cons: > > > >> 1) It creates an artifact in that PMD_REGISTER_DRIVER has to be used in one > > > >> compilation unit per DSO. As an example em and igb effectively merge two > > > >> drivers into one DSO, and the uses of PMD_REGISTER_DRIVER occur in two separate > > > >> C files for the same single linked DSO. Because of the use of the __COUNTER__ > > > >> macro we get multiple definitions of the same marker symbols. > > > >> > > > >> I would make the argument that the downside of the above artifact isn't that big > > > >> a deal. Traditionally in other projects a unit like a module (or DSO in our > > > >> case) only ever codifies a single driver (e.g. module_init() in the linux kernel > > > >> is only ever used once per built module). If we have code like igb/em that > > > >> shares some core code, we should build the shared code to object files and link > > > >> them twice, once to an em.so pmd and again to an igb.so pmd. > > It is also a problem for compilation units having PF and VF drivers. > > > > >> But regardless, I thought I would propose this to see what you all thought of > > > >> it. > > Thanks for proposing. > > > > - This implementation does not support binaries, so it is not suitable > > > for people who don't want dso, this is partially why I used bfd rather > > > than just dlopen. > > > > If you're statically linking an application, you should know what hardware you > > support already. Its going to be very hard, if not impossible to develop a > > robust solution that works with static binaries (the prior solutions don't work > > consistently with static binaries either). I really think the static solution > > needs to just be built into the application (i.e. the application needs to add a > > command line option to dump out the pci id's that are registered). > > No, we need a tool to know what are the supported devices before running > the application (e.g. for binding). > This tool should not behave differently depending of how DPDK was compiled > (static or shared). > > [...] > > > - How does it behave if we strip the dsos ? > > > > I described this above, its invariant to stripping, because the symbols for each > > pmd are explicitly exported, so strip doesn't touch the symbols that pmdinfo > > keys off of. > > > [...] > > > - The tool output format is not script friendly from my pov. > > > > Don't think it really needs to be script friendly, it was meant to provide human > > readable output, but script friendly output can be added easily enough if you > > want. > > Yes it needs to be script friendly. > > It appears that we must agree on a set of requirements first. > Please let's forget the implementation until we have collected enough > feedbacks on the needs. > I suggest these items to start the list: > > - query all drivers in static binary or shared library > - stripping resiliency > - human friendly > - script friendly > - show driver name > - list supported device id / name > - list driver options > - show driver version if available > - show dpdk version > - show kernel dependencies (vfio/uio_pci_generic/etc) > - room for extra information? > > Please ack or comment items of this list, thanks. That's quite a laundry list of requirements! I would view the following as core requirements: - query all drivers in static binary or shared library - stripping resiliency - human friendly - script friendly - show driver name - list supported device id / name and the rest as nice-to-have's that are not needed for a first version. That being said, I would expect those nice-to-have's to be fairly easy to add on once the base solution is in place. On a semi-related note, I assume this discussion and a solution here is not going to block the merging of the other clean-up patches in the driver/pci area? http://dpdk.org/ml/archives/dev/2016-April/037686.html http://dpdk.org/ml/archives/dev/2016-April/037708.html (Patches 1-10) Regards, /Bruce