From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from aserp1040.oracle.com ([141.146.126.69]:17972 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751229AbdAMWcb (ORCPT ); Fri, 13 Jan 2017 17:32:31 -0500 Date: Fri, 13 Jan 2017 17:30:35 -0500 From: Konrad Rzeszutek Wilk To: Dan Streetman Cc: Stefano Stabellini , jgross@suse.com, Boris Ostrovsky , Dan Streetman , Bjorn Helgaas , xen-devel@lists.xenproject.org, linux-kernel , linux-pci@vger.kernel.org Subject: Re: [PATCH] xen: do not re-use pirq number cached in pci device msi msg data Message-ID: <20170113223035.GE23066@char.us.oracle.com> References: <04f2a09f-59be-a720-bc98-4afb53171790@oracle.com> <20170113200751.20125-1-ddstreet@ieee.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20170113200751.20125-1-ddstreet@ieee.org> Sender: linux-pci-owner@vger.kernel.org List-ID: 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