From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753454AbbJGKZT (ORCPT ); Wed, 7 Oct 2015 06:25:19 -0400 Received: from mx1.redhat.com ([209.132.183.28]:38226 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751001AbbJGKZR (ORCPT ); Wed, 7 Oct 2015 06:25:17 -0400 Date: Wed, 7 Oct 2015 13:25:10 +0300 From: "Michael S. Tsirkin" To: Avi Kivity Cc: Avi Kivity , Vlad Zolotarov , linux-kernel@vger.kernel.org, hjk@hansjkoch.de, corbet@lwn.net, gregkh@linuxfoundation.org, bruce.richardson@intel.com, gleb@cloudius-systems.com, stephen@networkplumber.org, alexander.duyck@gmail.com Subject: Re: [PATCH v3 0/3] uio: add MSI/MSI-X support to uio_pci_generic driver Message-ID: <20151007084134-mutt-send-email-mst@redhat.com> References: <1443991398-23761-1-git-send-email-vladz@cloudius-systems.com> <20151005221651-mutt-send-email-mst@redhat.com> <56138867.4000006@cloudius-systems.com> <20151006171940-mutt-send-email-mst@redhat.com> <5613E4BE.6060802@cloudius-systems.com> <20151006181358-mutt-send-email-mst@redhat.com> <5613F227.9040401@scylladb.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5613F227.9040401@scylladb.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Oct 06, 2015 at 07:09:11PM +0300, Avi Kivity wrote: > > > On 10/06/2015 06:15 PM, Michael S. Tsirkin wrote: > >>While it is possible that userspace malfunctions and accidentally programs > >>MSI incorrectly, the risk is dwarfed by the ability of userspace to program > >>DMA incorrectly. > >That seems to imply that for the upstream kernel this is not a valid usecase at all. > > > > That is trivially incorrect, upstream pci_uio_generic is used with dpdk for > years. dpdk used to do polling for years. patch to use interrupts was posted in june 2015. > Are dpdk applications an invalid use case? The way dpdk is using UIO/sysfs is borderline at best, and can't be used to justify new interfaces. They have a more secure mode using VFIO. That one's more reasonable. -- MST