Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752799Ab3EUVtG (ORCPT ); Tue, 21 May 2013 17:49:06 -0400 Received: from mx1.redhat.com ([209.132.183.28]:57579 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752608Ab3EUVtD (ORCPT ); Tue, 21 May 2013 17:49:03 -0400 Date: Wed, 22 May 2013 00:49:12 +0300 From: "Michael S. Tsirkin" To: Don Dutile Cc: Alexander Duyck , Yinghai Lu , Bjorn Helgaas , Gu Zheng , "linux-pci@vger.kernel.org" , Linux Kernel Mailing List , NetDev Subject: Re: [PATCH 6/7] PCI: Make sure VF's driver get attached after PF's Message-ID: <20130521214912.GA21713@redhat.com> References: <1368498506-25857-1-git-send-email-yinghai@kernel.org> <1368498506-25857-7-git-send-email-yinghai@kernel.org> <51925FB0.4080504@intel.com> <5192946F.1050700@intel.com> <5192AEF4.1070905@intel.com> <519BE778.9040800@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <519BE778.9040800@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3258 Lines: 69 On Tue, May 21, 2013 at 05:30:32PM -0400, Don Dutile wrote: > On 05/14/2013 05:39 PM, Alexander Duyck wrote: > >On 05/14/2013 12:59 PM, Yinghai Lu wrote: > >>On Tue, May 14, 2013 at 12:45 PM, Alexander Duyck > >> wrote: > >>>On 05/14/2013 11:44 AM, Yinghai Lu wrote: > >>>>On Tue, May 14, 2013 at 9:00 AM, Alexander Duyck > >>>> wrote: > >>>>>I'm sorry, but what is the point of this patch? With device assignment > >>>>>it is always possible to have VFs loaded and the PF driver unloaded > >>>>>since you cannot remove the VFs if they are assigned to a VM. > >>>>unload PF driver will not call pci_disable_sriov? > >>>You cannot call pci_disable_sriov because you will panic all of the > >>>guests that have devices assigned. > >>ixgbe_remove did call pci_disable_sriov... > >> > >>for guest panic, that is another problem. > >>just like you pci passthrough with real pci device and hotremove the > >>card in host. > >> > >>... > > > >I suggest you take another look. In ixgbe_disable_sriov, which is the > >function that is called we do a check for assigned VFs. If they are > >assigned then we do not call pci_disable_sriov. > > > >> > >>>So how does your patch actually fix this problem? It seems like it is > >>>just avoiding it. > >>yes, until the first one is done. > > > >Avoiding the issue doesn't fix the underlying problem and instead you > >are likely just introducing more bugs as a result. > > > >>> From what I can tell your problem is originating in pci_call_probe. I > >>>believe it is calling work_on_cpu and that doesn't seem correct since > >>>the work should be taking place on a CPU already local to the PF. You > >>>might want to look there to see why you are trying to schedule work on a > >>>CPU which should be perfectly fine for you to already be doing your work on. > >>it always try to go with local cpu with same pxm. > > > >The problem is we really shouldn't be calling work_for_cpu in this case > >since we are already on the correct CPU. What probably should be > >happening is that pci_call_probe should be doing a check to see if the > >current CPU is already contained within the device node map and if so > >just call local_pci_probe directly. That way you can avoid deadlocking > >the system by trying to flush the CPU queue of the CPU you are currently on. > > > That's the patch that Michael Tsirkin posted for a fix, > but it was noted that if you have the case where the _same_ driver is used for vf & pf, > other deadlocks may occur. > It would work in the case of ixgbe/ixgbevf, but not for something like > the Mellanox pf/vf driver (which is the same). > I think our conclusion was this is a false positive for Mellanox. If not, we need to understand what the deadlock is better. > > > >Alex > >-- > >To unsubscribe from this list: send the line "unsubscribe linux-pci" in > >the body of a message to majordomo@vger.kernel.org > >More majordomo info at http://vger.kernel.org/majordomo-info.html -- 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/