From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753233AbbJFObD (ORCPT ); Tue, 6 Oct 2015 10:31:03 -0400 Received: from mx1.redhat.com ([209.132.183.28]:43516 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751727AbbJFObA (ORCPT ); Tue, 6 Oct 2015 10:31:00 -0400 Date: Tue, 6 Oct 2015 17:30:54 +0300 From: "Michael S. Tsirkin" To: Vlad Zolotarov Cc: linux-kernel@vger.kernel.org, hjk@hansjkoch.de, corbet@lwn.net, gregkh@linuxfoundation.org, bruce.richardson@intel.com, avi@cloudius-systems.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: <20151006171940-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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <56138867.4000006@cloudius-systems.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Oct 06, 2015 at 11:37:59AM +0300, Vlad Zolotarov wrote: > Bus mastering is easily enabled from the user space (taken from DPDK code): > > static int > pci_uio_set_bus_master(int dev_fd) > { > uint16_t reg; > int ret; > > ret = pread(dev_fd, ®, sizeof(reg), PCI_COMMAND); > if (ret != sizeof(reg)) { > RTE_LOG(ERR, EAL, > "Cannot read command from PCI config space!\n"); > return -1; > } > > /* return if bus mastering is already on */ > if (reg & PCI_COMMAND_MASTER) > return 0; > > reg |= PCI_COMMAND_MASTER; > > ret = pwrite(dev_fd, ®, sizeof(reg), PCI_COMMAND); > if (ret != sizeof(reg)) { > RTE_LOG(ERR, EAL, > "Cannot write command to PCI config space!\n"); > return -1; > } > > return 0; > } > > So, this is a non-issue. ;) There might be valid reasons for DPDK to do this, e.g. if using VFIO. I'm guessing it doesn't enable MSI though, does it? -- MST