From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: <alex@weka.io> Received: from mail-lb0-f172.google.com (mail-lb0-f172.google.com [209.85.217.172]) by dpdk.org (Postfix) with ESMTP id 971E87E7A for <dev@dpdk.org>; Tue, 21 Oct 2014 09:23:53 +0200 (CEST) Received: by mail-lb0-f172.google.com with SMTP id b6so496973lbj.17 for <dev@dpdk.org>; Tue, 21 Oct 2014 00:32:08 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:in-reply-to:references:date :message-id:subject:from:to:cc:content-type; bh=kMocZoDJ9uPjGv3YBWcVvkHpi+7vFdNcm+xhuSh0uF8=; b=UsSIbrt/UXByj3gmStct/ukGzxiATSwJ1gMCIlWTskYJrPcjBcmfjWMkNxOW6hMbOn /XqGbIL4AjHhgkA2iqRKRVuEeYTl/42PTY+DldKI1fY3nMLU9eYooJUx63CYCbOnvm2t 3HFSBnbCqbFK22R8I3XxooZIgfe9JlFZKekJ1X4sldzy/2xuBPRYIc0g2jrwjPCOdVoh 0mj5YPIWkOQ3IEeHzMxGBeV+IMUNW7oOF2zQyazugHaTYgG86lgNvA2I+NENlqM/wOR/ BsP925fL4mZ/mcjWP9+AYFIInsKva2rf9HMbfJykXz5+DPnIULD9MSMoPYPZRLJmEg+R DzuQ== X-Gm-Message-State: ALoCoQlf7ymWdrWF6i9AzkU75iTnTK6YJtD1Cgy+arY/BOkzpcK+2qGXIpPOKZWZrNHs+luCBQ1v MIME-Version: 1.0 X-Received: by 10.152.27.38 with SMTP id q6mr1189836lag.92.1413876728204; Tue, 21 Oct 2014 00:32:08 -0700 (PDT) Received: by 10.25.215.141 with HTTP; Tue, 21 Oct 2014 00:32:08 -0700 (PDT) In-Reply-To: <C37D651A908B024F974696C65296B57B0F2CD832@SHSMSX101.ccr.corp.intel.com> References: <CAKU5Fo_7fQHcYa-1ZBX8=D0SCkxZL8VLEpWYtJ6rG4DpV=g3gw@mail.gmail.com> <C37D651A908B024F974696C65296B57B0F2CD832@SHSMSX101.ccr.corp.intel.com> Date: Tue, 21 Oct 2014 10:32:08 +0300 Message-ID: <CAKfHP0U-v2fLQwyEa3KBZs3kXpVMQdLU+WgLzQq6xxmrb3Brtg@mail.gmail.com> From: Alex Markuze <alex@weka.io> To: "Xie, Huawei" <huawei.xie@intel.com> Content-Type: text/plain; charset=UTF-8 X-Content-Filtered-By: Mailman/MimeDel 2.1.15 Cc: "dev@dpdk.org" <dev@dpdk.org> Subject: Re: [dpdk-dev] Why do we need iommu=pt? X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: patches and discussions about DPDK <dev.dpdk.org> List-Unsubscribe: <http://dpdk.org/ml/options/dev>, <mailto:dev-request@dpdk.org?subject=unsubscribe> List-Archive: <http://dpdk.org/ml/archives/dev/> List-Post: <mailto:dev@dpdk.org> List-Help: <mailto:dev-request@dpdk.org?subject=help> List-Subscribe: <http://dpdk.org/ml/listinfo/dev>, <mailto:dev-request@dpdk.org?subject=subscribe> X-List-Received-Date: Tue, 21 Oct 2014 07:23:53 -0000 DPDK uses a 1:1 mapping and doesn't support IOMMU. IOMMU allows for simpler VM physical address translation. The second role of IOMMU is to allow protection from unwanted memory access by an unsafe devise that has DMA privileges. Unfortunately this protection comes with an extremely high performance costs for high speed nics. To your question iommu=pt disables IOMMU support for the hypervisor. On Tue, Oct 21, 2014 at 1:39 AM, Xie, Huawei <huawei.xie@intel.com> wrote: > > > > -----Original Message----- > > From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Shivapriya Hiremath > > Sent: Monday, October 20, 2014 2:59 PM > > To: dev@dpdk.org > > Subject: [dpdk-dev] Why do we need iommu=pt? > > > > Hi, > > > > My question is that if the Poll mode driver used the DMA kernel > interface > > to set up its mappings appropriately, would it still require that > iommu=pt > > be set? > > What is the purpose of setting iommu=pt ? > PMD allocates memory though hugetlb file system, and fills the physical > address > into the descriptor. > pt is used to pass through iotlb translation. Refer to the below link. > http://lkml.iu.edu/hypermail/linux/kernel/0906.2/02129.html > > > > Thank you. >