From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wg0-f48.google.com (mail-wg0-f48.google.com [74.125.82.48]) by dpdk.org (Postfix) with ESMTP id 6DC7A6A96 for ; Tue, 21 Oct 2014 18:45:49 +0200 (CEST) Received: by mail-wg0-f48.google.com with SMTP id k14so1871468wgh.19 for ; Tue, 21 Oct 2014 09:54:06 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :cc:content-type; bh=8wywneDoXtG3HpE2R36uBCL5WlEwN4l7z9xtEEkElcY=; b=vytyLjYtN1ixNRdjzRarotNDar31SV31bXbtwGaohtDVF0OnHHpk0to5MMN0Dvz78X r0s9ssUDZ35JIY13qSQ3lF2x+AmCZNsRLCvtMkSxuBZ2D0J8nGDbt+LfTk3hRbx7/rR7 8r1ukZtJEKC+J3IKutnxPAfvrvN+u9z+DX1uPAqeDeQnKTdHzQALpW9sUt3Zsc/TmAV3 d2LTdg5FX5yN75Glq80kysorJoBSB9ozSrTNjcIWCO/k9eVRgCab9V/SHM7nPjl2mVLD 8EUGNDGKKpRKwSfuHoTSUo/qweGy6sz9dLNo/9ZdGUlKO7bS9HaGH0uf4HDHX6lAMpoD PCdw== X-Received: by 10.180.104.8 with SMTP id ga8mr30368152wib.78.1413910444979; Tue, 21 Oct 2014 09:54:04 -0700 (PDT) MIME-Version: 1.0 Received: by 10.180.9.68 with HTTP; Tue, 21 Oct 2014 09:53:44 -0700 (PDT) In-Reply-To: References: From: Shivapriya Hiremath Date: Tue, 21 Oct 2014 09:53:44 -0700 Message-ID: To: Alex Markuze Content-Type: text/plain; charset=UTF-8 X-Content-Filtered-By: Mailman/MimeDel 2.1.15 Cc: "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 List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 21 Oct 2014 16:45:49 -0000 Hi, Thank you for all the replies. I am trying to understand the impact of this on DPDK. What will be the repercussions of disabling "iommu=pt" on the DPDK performance? On Tue, Oct 21, 2014 at 12:32 AM, Alex Markuze wrote: > 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 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. >> > >