Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754534AbaLDOb3 (ORCPT ); Thu, 4 Dec 2014 09:31:29 -0500 Received: from smtp.citrix.com ([66.165.176.89]:24280 "EHLO SMTP.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754338AbaLDObP (ORCPT ); Thu, 4 Dec 2014 09:31:15 -0500 X-IronPort-AV: E=Sophos;i="5.07,515,1413244800"; d="scan'208";a="199738434" Message-ID: <5480702F.2060004@citrix.com> Date: Thu, 4 Dec 2014 14:31:11 +0000 From: David Vrabel User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Icedove/31.2.0 MIME-Version: 1.0 To: Sander Eikelenboom CC: Konrad Rzeszutek Wilk , , , Boris Ostrovsky , , Subject: Re: [Xen-devel] [PATCH v5 9/9] xen/pciback: Implement PCI reset slot or bus with 'do_flr' SysFS attribute References: <201412041206.sB4C6XVQ009497@userz7022.oracle.com> <5480528F.8010106@citrix.com> <1107877503.20141204141054@eikelenboom.it> <548064EA.8090905@citrix.com> <308719815.20141204150909@eikelenboom.it> In-Reply-To: <308719815.20141204150909@eikelenboom.it> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit X-DLP: MIA1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/12/14 14:09, Sander Eikelenboom wrote: > > Thursday, December 4, 2014, 2:43:06 PM, you wrote: > >> On 04/12/14 13:10, Sander Eikelenboom wrote: >>> >>> Thursday, December 4, 2014, 1:24:47 PM, you wrote: >>> >>>> On 04/12/14 12:06, Konrad Rzeszutek Wilk wrote: >>>>> >>>>> On Dec 4, 2014 6:30 AM, David Vrabel wrote: >>>>>> >>>>>> On 03/12/14 21:40, Konrad Rzeszutek Wilk wrote: >>>>>>> >>>>>>> Instead of doing all this complex dance, we depend on the toolstack >>>>>>> doing the right thing. As such implement the 'do_flr' SysFS attribute >>>>>>> which 'xl' uses when a device is detached or attached from/to a guest. >>>>>>> It bypasses the need to worry about the PCI lock. >>>>>> >>>>>> No. Get pciback to add its own "reset" sysfs file (as I have repeatedly >>>>>> proposed). >>>>>> >>>>> >>>>> Which does not work as the kobj will complain (as there is already an 'reset' associated with the PCI device). >>> >>>> It is only needed if the core won't provide one. >>> >>>> +static int pcistub_try_create_reset_file(struct pci_dev *pci) >>>> +{ >>>> + struct xen_pcibk_dev_data *dev_data = pci_get_drvdata(pci); >>>> + struct device *dev = &pci->dev; >>>> + int ret; >>>> + >>>> + /* Already have a per-function reset? */ >>>> + if (pci_probe_reset_function(pci) == 0) >>>> + return 0; >>>> + >>>> + ret = device_create_file(dev, &dev_attr_reset); >>>> + if (ret < 0) >>>> + return ret; >>> + dev_data->>created_reset_file = true; >>>> + return 0; >>>> +} >>> >>> Wouldn't the "core-reset-sysfs-file" be still wired to the end up calling >>> "pci.c:__pci_dev_reset" ? >>> >>> The problem with that function is that from my testing it seems that the >>> first option "pci_dev_specific_reset" always seems to return succes, so all the >>> other options are skipped (flr, pm, slot, bus). However the device it self is >>> not properly reset enough (perhaps the pci_dev_specific_reset is good enough for >>> none virtualization purposes and it's probably the least intrusive. For >>> virtualization however it would be nice to be sure it resets properly, or have a >>> way to force a specific reset routine.) > >> Then you need work with the maintainer for those specific devices or >> drivers to fix their specific reset function. > >> I'm not adding stuff to pciback to workaround broken quirks. > > OK that's a pretty clear message there, so if one wants to use pci and vga > passthrough one should better use KVM and vfio-pci. Have you (or anyone else) ever raised the problem with the broken reset quirk for certain devices with the relevant maintainer? > vfio-pci has: > - logic to do the try-slot-bus-reset logic Just because vfio-pci fixed it incorrectly doesn't mean pciback has to as well. It makes no sense for both pciback and vfio-pci to workaround problems with pci_function_reset() in different ways -- it should be fixed in the core PCI code so both can benefit and make use of the same code. David -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/