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 9D7F21CB45 for ; Thu, 5 Apr 2018 13:30:53 +0200 (CEST) X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga005.jf.intel.com ([10.7.209.41]) by fmsmga102.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 05 Apr 2018 04:30:52 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.48,411,1517904000"; d="scan'208";a="214145924" Received: from aburakov-mobl.ger.corp.intel.com (HELO [10.237.220.128]) ([10.237.220.128]) by orsmga005.jf.intel.com with ESMTP; 05 Apr 2018 04:30:48 -0700 To: dev@dpdk.org Cc: Bruce Richardson , keith.wiles@intel.com, jianfeng.tan@intel.com, andras.kovacs@ericsson.com, laszlo.vadkeri@ericsson.com, benjamin.walker@intel.com, thomas@monjalon.net, konstantin.ananyev@intel.com, kuralamudhan.ramakrishnan@intel.com, louise.m.daly@intel.com, nelio.laranjeiro@6wind.com, yskoh@mellanox.com, pepperjo@japf.ch, jerin.jacob@caviumnetworks.com, hemant.agrawal@nxp.com, olivier.matz@6wind.com, shreyansh.jain@nxp.com, gowrishankar.m@linux.vnet.ibm.com, Pawel Wodkowski References: <0de49c396f7e2c0651acb4cc4a575919234f4c8d.1522797505.git.anatoly.burakov@intel.com> From: "Burakov, Anatoly" Message-ID: <21db37b3-c9ea-7994-a2f7-639f69f2ab32@intel.com> Date: Thu, 5 Apr 2018 12:30:47 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 MIME-Version: 1.0 In-Reply-To: <0de49c396f7e2c0651acb4cc4a575919234f4c8d.1522797505.git.anatoly.burakov@intel.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Subject: Re: [dpdk-dev] [PATCH v3 46/68] vfio: allow to map other memory regions 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: Thu, 05 Apr 2018 11:30:54 -0000 On 04-Apr-18 12:21 AM, Anatoly Burakov wrote: > Currently it is not possible to use memory that is not owned by DPDK to > perform DMA. This scenarion might be used in vhost applications (like > SPDK) where guest send its own memory table. To fill this gap provide > API to allow registering arbitrary address in VFIO container. > > Signed-off-by: Pawel Wodkowski > Signed-off-by: Anatoly Burakov > Signed-off-by: Gowrishankar Muthukrishnan > --- @Gowrishankar, We've discussed this privately already, but just to make sure it is publicly stated: as it is, parts of this patchset for PPC64 have potential issues with them. Unmapping and remapping the entire segment list on alloc introduces a race condition - what if a DMA request comes in while we're in the middle of remapping? We cannot realistically stop NICs from doing DMA while some other thread is allocating memory. There is also a larger issue that i've raised in a previous response to this patch [1], and PPC64 will will have this problem worse, because not only the described issue will happen on hot-unplug/hotplug, but it may also happen during regular allocations, because PPC64 IOMMU will drop all mappings on window resize. [1] http://dpdk.org/ml/archives/dev/2018-April/095182.html -- Thanks, Anatoly