From mboxrd@z Thu Jan 1 00:00:00 1970 From: Don Dutile Subject: Re: [PATCH 6/7] PCI: Make sure VF's driver get attached after PF's Date: Tue, 21 May 2013 17:30:32 -0400 Message-ID: <519BE778.9040800@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> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Yinghai Lu , Bjorn Helgaas , Gu Zheng , "linux-pci@vger.kernel.org" , Linux Kernel Mailing List , NetDev , "Michael S. Tsirkin" To: Alexander Duyck Return-path: In-Reply-To: <5192AEF4.1070905@intel.com> Sender: linux-pci-owner@vger.kernel.org List-Id: netdev.vger.kernel.org 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). > > 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