From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752352AbbJEMoH (ORCPT ); Mon, 5 Oct 2015 08:44:07 -0400 Received: from SMTP.ANDREW.CMU.EDU ([128.2.105.202]:60684 "EHLO smtp.andrew.cmu.edu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751501AbbJEMoF (ORCPT ); Mon, 5 Oct 2015 08:44:05 -0400 Date: Mon, 5 Oct 2015 08:43:46 -0400 From: "Gabriel L. Somlo" To: Mark Rutland Cc: Paolo Bonzini , gregkh@linuxfoundation.org, paul@pwsan.com, galak@codeaurora.org, will.deacon@arm.com, agross@codeaurora.org, zajec5@gmail.com, hanjun.guo@linaro.org, catalin.marinas@arm.com, linux-api@vger.kernel.org, linux-kernel@vger.kernel.org, kernelnewbies@kernelnewbies.org, matt.fleming@intel.com, lersek@redhat.com, jordan.l.justen@intel.com, mst@redhat.com, peter.maydell@linaro.org, leif.lindholm@linaro.org, ard.biesheuvel@linaro.org, kraxel@redhat.com, qemu-devel@nongnu.org Subject: Re: [PATCH v3 0/4] SysFS driver for QEMU fw_cfg device Message-ID: <20151005124346.GG1977@HEDWIG.INI.CMU.EDU> References: <1443914889-9619-1-git-send-email-somlo@cmu.edu> <20151005100035.GA19064@leverpostej> <561263A4.2020304@redhat.com> <20151005122332.GK19064@leverpostej> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20151005122332.GK19064@leverpostej> X-Clacks-Overhead: GNU Terry Pratchett User-Agent: Mutt/1.5.23 (2014-03-12) X-PMX-Version: 6.0.3.2322014, Antispam-Engine: 2.7.2.2107409, Antispam-Data: 2015.10.5.123317 X-SMTP-Spam-Clean: 8% ( MULTIPLE_RCPTS 0.1, HTML_00_01 0.05, HTML_00_10 0.05, BODYTEXTP_SIZE_3000_LESS 0, BODY_SIZE_1700_1799 0, BODY_SIZE_2000_LESS 0, BODY_SIZE_5000_LESS 0, BODY_SIZE_7000_LESS 0, DATE_TZ_NA 0, FROM_EDU_TLD 0, NO_URI_FOUND 0, NO_URI_HTTPS 0, REFERENCES 0, __BOUNCE_CHALLENGE_SUBJ 0, __BOUNCE_NDR_SUBJ_EXEMPT 0, __CD 0, __CT 0, __CT_TEXT_PLAIN 0, __FORWARDED_MSG 0, __HAS_FROM 0, __HAS_MSGID 0, __IN_REP_TO 0, __MIME_TEXT_ONLY 0, __MIME_VERSION 0, __MULTIPLE_RCPTS_CC_X2 0, __PHISH_SPEAR_STRUCTURE_1 0, __REFERENCES 0, __SANE_MSGID 0, __SUBJ_ALPHA_END 0, __SUBJ_ALPHA_NEGATE 0, __TO_MALFORMED_2 0, __USER_AGENT 0) X-SMTP-Spam-Score: 8% Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Oct 05, 2015 at 01:23:33PM +0100, Mark Rutland wrote: > On Mon, Oct 05, 2015 at 01:48:52PM +0200, Paolo Bonzini wrote: > > > > > > On 05/10/2015 12:00, Mark Rutland wrote: > > > Some of the keys in the example look like they'd come from other sources > > > (e.g. the *-tables entries), while others look like kernel/bootloader > > > configuration options (e.g. etc/boot-fail-wait, bootorder) -- I'm > > > concerned about redundancy here. > > > > The redundancy is because the firmware and the bootloader actually > > _consume_ these fw_cfg strings to produce the others (the ACPI tables, > > the kernel configuration options). > > > > On the other hand, hiding some strings just because they ought to have > > been consumed already makes little sense. > > Sure. However, I'm concerned that providing redundant interfaces for > those could lead to people grabbing information from here (because it's > convenient) rather than the existing canonical locations, which means we > get more software that works on fewer systems for no good reason. > > What I couldn't figure out was what _additional_ information this > provided; it looked like a mixed bag of details we could already get > from disparate sources. If that's all it does, then it seems to me like > it doesn't add any benefit and potentially makes things worse. > > So what do we get from this interface that we cannot get elsewhere, and > why is this the best way of exposing it? Starting with qemu 2.4, it is possible to insert arbitrary named blobs into fw_cfg from the qemu command line. *Those* entries might be interesting to userspace, which is why it might be handy to access to fw_cfg blobs in general. Thanks, --Gabriel