From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752517AbdECXT4 (ORCPT ); Wed, 3 May 2017 19:19:56 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:37712 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751447AbdECXTr (ORCPT ); Wed, 3 May 2017 19:19:47 -0400 Date: Wed, 3 May 2017 16:19:38 -0700 From: Greg KH To: Stefano Stabellini Cc: Boris Ostrovsky , David Woodhouse , Bjorn Helgaas , stable@vger.kernel.org, Juergen Gross , linux-pci@vger.kernel.org, linux-kernel , Bjorn Helgaas , xen-devel@lists.xenproject.org, Dan Streetman , Dan Streetman Subject: Re: [Xen-devel] [PATCH] xen: do not re-use pirq number cached in pci device msi msg data Message-ID: <20170503231938.GA1211@kroah.com> References: <0c2b4d6a-93e7-90a2-ffaf-fa423fb022d5@suse.com> <72f8b025-e858-5e54-d900-50fbec46fea6@oracle.com> <20170222142810.GA28359@bhelgaas-glaptop.roam.corp.google.com> <3379a82f-04b7-152a-1577-bf99b1c638cc@oracle.com> <1493835543.4904.5.camel@infradead.org> <1b84c2a5-1fd6-02b9-c080-0f99f6a8d085@oracle.com> <20170503230635.GB11256@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.8.2 (2017-04-18) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, May 03, 2017 at 04:12:29PM -0700, Stefano Stabellini wrote: > On Wed, 3 May 2017, Greg KH wrote: > > On Wed, May 03, 2017 at 03:59:15PM -0700, Stefano Stabellini wrote: > > > On Wed, 3 May 2017, Boris Ostrovsky wrote: > > > > On 05/03/2017 02:19 PM, David Woodhouse wrote: > > > > > On Wed, 2017-02-22 at 10:14 -0500, Boris Ostrovsky wrote: > > > > >> On 02/22/2017 09:28 AM, Bjorn Helgaas wrote: > > > > >>> On Tue, Feb 21, 2017 at 10:58:39AM -0500, Boris Ostrovsky wrote: > > > > >>>> On 02/21/2017 10:45 AM, Juergen Gross wrote: > > > > >>>>> On 21/02/17 16:31, Dan Streetman wrote: > > > > >>>>>> On Fri, Jan 13, 2017 at 5:30 PM, Konrad Rzeszutek Wilk > > > > >>>>>> wrote: > > > > >>>>>>> On Fri, Jan 13, 2017 at 03:07:51PM -0500, Dan Streetman wrote: > > > > >>>>>>>> Revert the main part of commit: > > > > >>>>>>>> af42b8d12f8a ("xen: fix MSI setup and teardown for PV on HVM guests") > > > > >>>>>>>> > > > > >>>>>>>> That commit introduced reading the pci device's msi message data to see > > > > >>>>>>>> if a pirq was previously configured for the device's msi/msix, and re-use > > > > >>>>>>>> that pirq. At the time, that was the correct behavior. However, a > > > > >>>>>>>> later change to Qemu caused it to call into the Xen hypervisor to unmap > > > > >>>>>>>> all pirqs for a pci device, when the pci device disables its MSI/MSIX > > > > >>>>>>>> vectors; specifically the Qemu commit: > > > > >>>>>>>> c976437c7dba9c7444fb41df45468968aaa326ad > > > > >>>>>>>> ("qemu-xen: free all the pirqs for msi/msix when driver unload") > > > > >>>>>>>> > > > > >>>>>>>> Once Qemu added this pirq unmapping, it was no longer correct for the > > > > >>>>>>>> kernel to re-use the pirq number cached in the pci device msi message > > > > >>>>>>>> data. All Qemu releases since 2.1.0 contain the patch that unmaps the > > > > >>>>>>>> pirqs when the pci device disables its MSI/MSIX vectors. > > > > >>>>>>>> > > > > >>>>>>>> This bug is causing failures to initialize multiple NVMe controllers > > > > >>>>>>>> under Xen, because the NVMe driver sets up a single MSIX vector for > > > > >>>>>>>> each controller (concurrently), and then after using that to talk to > > > > >>>>>>>> the controller for some configuration data, it disables the single MSIX > > > > >>>>>>>> vector and re-configures all the MSIX vectors it needs. So the MSIX > > > > >>>>>>>> setup code tries to re-use the cached pirq from the first vector > > > > >>>>>>>> for each controller, but the hypervisor has already given away that > > > > >>>>>>>> pirq to another controller, and its initialization fails. > > > > >>>>>>>> > > > > >>>>>>>> This is discussed in more detail at: > > > > >>>>>>>> https://lists.xen.org/archives/html/xen-devel/2017-01/msg00447.html > > > > >>>>>>>> > > > > >>>>>>>> Fixes: af42b8d12f8a ("xen: fix MSI setup and teardown for PV on HVM guests") > > > > >>>>>>>> Signed-off-by: Dan Streetman > > > > >>>>>>> Acked-by: Konrad Rzeszutek Wilk > > > > >>>>>> This doesn't seem to be applied yet, is it still waiting on another > > > > >>>>>> ack? Or maybe I'm looking at the wrong git tree... > > > > >>>>> Am I wrong or shouldn't this go through the PCI tree? Konrad? > > > > >>>> Konrad is away this week but since pull request for Xen tree just went > > > > >>>> out we should probably wait until rc1 anyway (unless something big comes > > > > >>>> up before that). > > > > >>> I assume this should go via the Xen or x86 tree, since that's how most > > > > >>> arch/x86/pci/xen.c patches have been handled, including af42b8d12f8a. > > > > >>> If you think otherwise, let me know. > > > > >> OK, I applied it to Xen tree's for-linus-4.11. > > > > > Hm, we want this (c74fd80f2f4) in stable too, don't we? > > > > > > > > > > > > Maybe. > > > > > > > > Per https://lists.xen.org/archives/html/xen-devel/2017-01/msg00987.html > > > > it may break things on older (4.4-) hypervisors. They are out of > > > > support, which is why this patch went in now but I am not sure this > > > > automatically applies to stable kernels. > > > > > > > > Stefano? > > > > > > This is a difficult call. We could just say that all the broken Xen > > > versions are out of support, so let's fix all the Linux kernel stable > > > trees that we can. > > > > > > Or we could give a look at the release dates. Linux 3.18 is still > > > maintained and was tagged on Dec 7 2014. > > > > Don't do anything "special" for 3.18 if you have to. I'm only > > semi-maintaining it because some SoC vendors never upstreamed their > > trees and lots of devices rely on it. None of them use Xen on their > > platforms, so no need for me to backport any change there. > > Thanks Greg, that is good info. Is 4.4 the oldest Linux tree fully > maintained? Well, the one that _I_ fully maintain :) There are some older ones, but you are free to say how far back any patch should go, you're the maintainers of this code, not me... thanks, greg k-h