From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-vk0-f49.google.com (mail-vk0-f49.google.com [209.85.213.49]) by dpdk.org (Postfix) with ESMTP id 7292F2BD0 for ; Sun, 4 Sep 2016 10:08:47 +0200 (CEST) Received: by mail-vk0-f49.google.com with SMTP id f76so56533013vke.0 for ; Sun, 04 Sep 2016 01:08:47 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=netronome-com.20150623.gappssmtp.com; s=20150623; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :cc; bh=PvgCQkwrzk9eoj40OMRSvrfNzRg+6Yau1bIdZ8QuJtI=; b=jEaAWOcWBXnmBYsTWNzwIUAMM18RvKjjDT0u1p+gBLZk/5+wO24z/Vtc1TuVIluTs7 Dd+rXqMt2shccUYw6+YONcdF7bFCWAP9xLomkpBlO1FMfkSSX7PXCHJ646TTGbrP0ZOS Iiy3MHDi8sczdR6LeEUIfincB0HywfeEaCFY2KsFRNRzMjzqdIA1rz0KUgobkrwlUvEW zaje3iGYKYFd4oX2SFpcweB71QMr/qQOvM/vwyJ1pOG99bpsCSm0V+1L5yLcLyksmsdv t/PINyNUVxxJy1XJv3vL/oEKLZ86V1HFoDulMtsX+fZJiTJv0hr37aMAy74/FH0Q4fLV 2OJw== 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:from:date :message-id:subject:to:cc; bh=PvgCQkwrzk9eoj40OMRSvrfNzRg+6Yau1bIdZ8QuJtI=; b=M5cX/HW1zns8607hGHEF5GTAA1RubRB3aI2DSINm8Md+kSX/DPa/GHw4HmkLqMGOjk uY4L7ZWcZKOxF/J233ddC6T1cS3cNG0XWm6DiZqAqGQ9uomcWdOd31HLTiuFtUE44ETZ IrvBuZtp3HdDAflLUQrFeiD9gsb/ft8aO694+i/6ZzXuUY9mDHMYHbycbOngkEU6qc8l D4tVui8swf5d2T5dJIbdOw+pP9AtL7Dv56me/0vo4Y1d6TXrtyAjL4vJQOIlP5xPHyJG Ssi/OHyJqhlV1+/XH9FzEMfokpdCMw8fZGFkpF8uK6tZAKaBXxvqfY6/SN0rKOWlWxLu f7Ag== X-Gm-Message-State: AE9vXwN7Vhw3+Yu0PETXrmSm7rMhs6y88sT01XF4V9yW6DdSSiJU/EYo1M0qFm6xmuwmrSuUqAJZQs0Pizuujdst X-Received: by 10.31.52.193 with SMTP id b184mr16124033vka.16.1472976526796; Sun, 04 Sep 2016 01:08:46 -0700 (PDT) MIME-Version: 1.0 Received: by 10.103.117.22 with HTTP; Sun, 4 Sep 2016 01:08:46 -0700 (PDT) In-Reply-To: <20160902202613-mutt-send-email-mst@kernel.org> References: <1472798220-7121-1-git-send-email-jasowang@redhat.com> <1472798220-7121-2-git-send-email-jasowang@redhat.com> <1631660.hGMgJuvotI@xps13> <20160902202613-mutt-send-email-mst@kernel.org> From: Alejandro Lucero Date: Sun, 4 Sep 2016 09:08:46 +0100 Message-ID: To: "Michael S. Tsirkin" Cc: Thomas Monjalon , Jason Wang , dev , huawei.xie@intel.com, yuanhan.liu@linux.intel.com Content-Type: text/plain; charset=UTF-8 X-Content-Filtered-By: Mailman/MimeDel 2.1.15 Subject: Re: [dpdk-dev] [PATCH 2/2] virtio: support IOMMU platform 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: Sun, 04 Sep 2016 08:08:47 -0000 I know RedHat is working on a vIOMMU so I guess this work is related to that effort, but it is a surprise virtio using IOMMU. I thought IOMMU just made sense when using SRIOV. My second guess is using IOMMU with virtio is a matter of security, but by other hand, virtio + IOMMU could imply serious performance degradation when multiple VMs are in use. I'm talking about IOMMU contention, exactly about IOTLB contention. This performance issue is complex to describe or even analyze as there are several factors having an impact on it. For example, 1GB hugepages can avoid most of it and the same if TX & RX rings are not bigger than 256. So, my question: is RedHat aware of this potential IOMMU contention which can limit scalability? On Fri, Sep 2, 2016 at 6:26 PM, Michael S. Tsirkin wrote: > On Fri, Sep 02, 2016 at 03:04:56PM +0200, Thomas Monjalon wrote: > > 2016-09-02 14:37, Jason Wang: > > > Virtio pmd doesn't support VFIO in the past since devices bypass IOMMU > > > completely. But recently, the work of making virtio device work with > > > IOMMU is near to complete. > > > > Good news! > > What are the requirements for Qemu and Linux version numbers please? > > I expect QEMU 2.8 and Linux 4.8 to have the support. >