From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [dpdk-dev] [PATCH] vfio: Include No-IOMMU mode Date: Wed, 2 Dec 2015 18:31:53 +0200 Message-ID: <20151202182704-mutt-send-email-mst@redhat.com> References: <20151028211309.14155.23867.stgit@gimli.home> <564A0E70.4030409@scylladb.com> <1449070123.15753.35.camel@redhat.com> <1473285.yZJWhu9CPo@xps13> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: Avi Kivity , gleb-VrcmuVmyx1hWk0Htik3J/w@public.gmane.org, corbet-T1hC0tSOHrs@public.gmane.org, dev-VfR2kkLFssw@public.gmane.org, gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, hjk-vqZO0P4V72/QD6PfKP4TzA@public.gmane.org To: Thomas Monjalon Return-path: Content-Disposition: inline In-Reply-To: <1473285.yZJWhu9CPo@xps13> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org List-Id: dev.dpdk.org On Wed, Dec 02, 2015 at 05:19:18PM +0100, Thomas Monjalon wrote: > Hi, > > 2015-12-02 08:28, Alex Williamson: > > On Mon, 2015-11-16 at 19:12 +0200, Avi Kivity wrote: > > > On 11/16/2015 07:06 PM, Alex Williamson wrote: > > > > FYI, this is now in v4.4-rc1 (the slightly modified v2 version). I want > > > > to give fair warning though that while we seem to agree on this idea, it > > > > hasn't been proven with a userspace driver port. I've opted to include > > > > it in this merge window rather than delaying it until v4.5, but I really > > > > need to see a user for this before the end of the v4.4 cycle or I think > > > > we'll need to revert and revisit for v4.5 anyway. I don't really have > > > > any interest in adding and maintaining code that has no users. Please > > > > keep me informed of progress with a dpdk port. Thanks, > > > > > > Thanks Alex. Copying the dpdk mailing list, where the users live. > > > > > > dpdk-ers: vfio-noiommu is a replacement for uio_pci_generic and > > > uio_igb. It supports MSI-X and so can be used on SR/IOV VF devices. > > > The intent is that you can use dpdk without an external module, using > > > vfio, whether you are on bare metal with an iommu, bare metal without an > > > iommu, or virtualized. However, dpdk needs modification to support this. > > > > Still no users for this that I'm aware of. I'm going to revert this in > > rc5 unless something changes. Thanks, > > Removing needs for out-of-tree modules is a really nice achievement. > Yes, we (in the DPDK project) should check how to use this no-iommu VFIO > and to replace igb_uio. > > I'm sorry we failed to catch your email and follow up. > Is it really too late? What is the risk of keeping it in Linux 4.4? > Advertising a new feature and removing it would be frustrating. > > Have you tried this VFIO mode with DPDK? > How complex would be the patch to support it? > > Thanks These things need to be developed together, one can't be sure it meets userspace needs if no one tried. And then where would we be? Supporting a broken interface forever. If someone writes the userspace code, then this feature can come back for 4.5. -- MST