From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga03.intel.com (mga03.intel.com [134.134.136.65]) by dpdk.org (Postfix) with ESMTP id 77EED2935 for ; Fri, 14 Jul 2017 12:59:57 +0200 (CEST) Received: from fmsmga005.fm.intel.com ([10.253.24.32]) by orsmga103.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 14 Jul 2017 03:59:57 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.40,358,1496127600"; d="scan'208";a="126647112" Received: from smonroyx-mobl.ger.corp.intel.com (HELO [10.252.25.6]) ([10.252.25.6]) by fmsmga005.fm.intel.com with ESMTP; 14 Jul 2017 03:59:55 -0700 To: Aaron Conole , dev@openvswitch.org References: <20170705175634.7957-1-aconole@redhat.com> Cc: dev@dpdk.org, Flavio Leitner , Ansis Atteka From: Sergio Gonzalez Monroy Message-ID: <2125110d-06ee-715e-e8f4-71e745ba310b@intel.com> Date: Fri, 14 Jul 2017 11:59:54 +0100 User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.1.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [dpdk-dev] [ovs-dev] [PATCH v2 0/4] rhel/fedora: non-root OvS out of the box 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, 14 Jul 2017 10:59:59 -0000 On 11/07/2017 20:21, Aaron Conole wrote: > Aaron Conole writes: > >> Aaron Conole writes: >> >>> This series attempts to introduce the ability to start and use >>> Open vSwitch 'out of the box' as a non-root user. It does this by >>> modifying the service files to pass the recently introduced --ovs-user >>> argument around, and by making some minor tweaks to the passwd, group, >>> and filesystem information. >>> >>> I prefixed the packaging work with 'redhat', but if rpm or packaging >>> is a preferred prefx for that work, I can respin. >>> >>> The more controversial changes are: >>> >>> * This modifies the /etc/sysconfig/ file on install. >>> * The dpdk support directly modifies /dev/hugepages with a call to chmod >>> * A new user 'openvswitch', and up to two new groups 'openvswitch', and >>> 'hugetlbfs' are created >>> * A change to soexpand.pl to allow conditional inclusion of dpdk-related >>> options >>> >> An interesting development has occurred while testing this series. >> >> It seems that as part of a rowhammer mitigation, access to >> /proc/self/pagemap ends up being restricted. This makes DPDK break in a >> catastrophic way. >> >> One way of mitigating this is to keep the CAP_SYS_ADMIN capability when >> DPDK is enabled (not sure whether it would be a runtime or compile >> time change). This means we end up keeping many root-user level >> permissions that we probably shouldn't need or want. I was thinking >> that when DPDK is compiled in, we would keep the CAP_SYS_ADMIN for the >> first iteration of DB synchronization, and then drop it after calling >> DPDK-init. That would prevent lazy loading, or being able to turn it >> on without restarting the daemon (which I don't like). >> >> Another is to say that if DPDK is enabled at compile time, just don't >> drop permissions at all. That approach seems really wrong, but it's a >> possibility. >> >> Not sure what else can be done from the OvS side for this. I think it >> could be possible to do something where before dropping privs, we cache >> the pagemap and then feed it to DPDK during initialization, but that >> will require work from DPDK side, and I'm not sure if it actually works >> with DPDK (because I haven't looked into why the pagemap is being read >> to begin with). >> >> So, I'm a bit stuck on this work, and asking for some opinions. >> > UPDATE: it seems that with DPDK 17.02+, this has been resolved. I'll > wait for resubmit until after the following commit has been applied: > > https://mail.openvswitch.org/pipermail/ovs-dev/2017-July/334893.html > As you mentioned, DPDK needs CAP_SYS_ADMIN to be able to *read* /proc/self/pagemap. The goal is to get the physical address of the hugepages we are using. Since DPDK 17.05 (commit below) we are able to run non-root if we have an IOMMU, but we still need CAP_SYS_ADMIN if we do not have an IOMMU as we need those physical addresses for DMA. commit cdc242f260e766bd95a658b5e0686a62ec04f5b0 Author: Ben Walker Date: Tue Jan 31 10:44:53 2017 -0700 eal/linux: support running as unprivileged user For Linux kernel 4.0 and newer, the ability to obtain physical page frame numbers for unprivileged users from /proc/self/pagemap was removed. Instead, when an IOMMU is present, simply choose our own DMA addresses instead. Signed-off-by: Ben Walker I have not tried myself but I think you suggestion of dropping privileges after eal_init should work given that currently is the only time we parse /proc/self/pagemap Thanks, Sergio