From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thomas Monjalon Subject: Re: VFIO no-iommu Date: Thu, 17 Dec 2015 11:09:23 +0100 Message-ID: <2580440.9rYeIQLTBH@xps13> References: <60420822.AbcfvjLZCk@xps13> <17700135.Qc9aIsHGGP@xps13> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7Bit Cc: dev@dpdk.org To: "Burakov, Anatoly" Return-path: Received: from mail-wm0-f44.google.com (mail-wm0-f44.google.com [74.125.82.44]) by dpdk.org (Postfix) with ESMTP id EA27B8D3A for ; Thu, 17 Dec 2015 11:10:39 +0100 (CET) Received: by mail-wm0-f44.google.com with SMTP id p187so15933340wmp.0 for ; Thu, 17 Dec 2015 02:10:39 -0800 (PST) In-Reply-To: List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" Hi, 2015-12-17 09:52, Burakov, Anatoly: > > > > > On Tue, Dec 15, 2015 at 09:53:18AM -0700, Alex Williamson wrote: > > > > > So it works. Is it acceptable? Useful? Sufficiently complete? > > > > > Does it imply deprecating the uio interface? I believe the > > > > > feature that started this discussion was support for MSI/X > > > > > interrupts so that VFs can support some kind of interrupt (uio > > > > > only supports INTx since it doesn't allow DMA). Implementing that > > > > > would be the ultimate test of whether this provides dpdk with not > > > > > only a more consistent interface, but the feature dpdk wants > > > > > that's missing in uio. Thanks, > > > > > > Ferruh has done a great job so far testing Alex's patch, very few changes > > from DPDK side seem to be required as far as existing functionality goes (not > > sure about VF interrupts mentioned by Alex). However, one thing that > > concerns me is usability. While it is true that no-IOMMU mode in VFIO would > > mean uio interfaces could be deprecated in time, the no-iommu mode is way > > more hassle than using igb_uio/uio_pci_generic because it will require a > > kernel recompile as opposed to simply compiling and insmod'ding an out-of- > > tree driver. So, in essence, if you don't want an IOMMU, it's becoming that > > much harder to use DPDK. Would that be something DPDK is willing to live > > with in the absence of uio interfaces? > > > > Excuse me if I missed something obvious. > > Why a kernel compilation is needed? > > Well, not really full kernel compilation, but in the default configuration, VFIO driver would not support NOIOMMU mode. I.e. it's not compiled by default. Support for no-iommu should be enabled in kernel config and compiled in. So, whoever is going to use DPDK with VFIO-no-iommu will have to download kernel tree and recompile the VFIO module and install it. That's obviously way more hassle than simply compiling an out-of-tree driver that's already included and works with an out-of-the-box kernel. The "out-of-the-box kernel" is configured by your distribution. So we don't know yet what will be their choice. If the distribution supports DPDK, it should be enabled.