From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Return-Path: Subject: Re: [Xen-devel] [PATCH] xen: do not re-use pirq number cached in pci device msi msg data To: David Woodhouse , Bjorn Helgaas , stable@vger.kernel.org, Stefano Stabellini References: <04f2a09f-59be-a720-bc98-4afb53171790@oracle.com> <20170113200751.20125-1-ddstreet@ieee.org> <20170113223035.GE23066@char.us.oracle.com> <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> Cc: Juergen Gross , linux-pci@vger.kernel.org, linux-kernel , Bjorn Helgaas , xen-devel@lists.xenproject.org, Dan Streetman , Dan Streetman From: Boris Ostrovsky Message-ID: <1b84c2a5-1fd6-02b9-c080-0f99f6a8d085@oracle.com> Date: Wed, 3 May 2017 14:43:15 -0400 MIME-Version: 1.0 In-Reply-To: <1493835543.4904.5.camel@infradead.org> Content-Type: text/plain; charset=utf-8 List-ID: 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? -boris