On 04/29/2014 07:37 PM, Wei Yang wrote: > On Tue, Apr 29, 2014 at 05:55:48PM +1000, Alexey Kardashevskiy wrote: >> On 04/29/2014 04:49 PM, Wei Yang wrote: >>> On Mon, Apr 28, 2014 at 11:35:32PM +1000, Alexey Kardashevskiy wrote: >>>> On 04/23/2014 12:26 PM, Wei Yang wrote: >>>>> During the EEH hotplug event, iommu_add_device() will be invoked three >>>>> times >>>>> and two of them will trigger warning or error. >>>>> >>>>> The three times to invoke the iommu_add_device() are: >>>>> >>>>> pci_device_add >>>>> ... >>>>> set_iommu_table_base_and_group <- 1st time, fail >>>>> device_add >>>>> ... >>>>> tce_iommu_bus_notifier <- 2nd time, succees >>>>> pcibios_add_pci_devices >>>>> ... >>>>> pcibios_setup_bus_devices <- 3rd time, re-attach >>>>> >>>>> The first time fails, since the dev->kobj->sd is not initialized. The >>>>> dev->kobj->sd is initialized in device_add(). >>>>> The third time's warning is triggered by the re-attach of the iommu_group. >>>>> >>>>> After applying this patch, the error >>>> >>>> Nack. >>>> >>>> The patch still seems incorrect and we actually need to remove >>>> tce_iommu_bus_notifier completely as pcibios_setup_bus_devices is called >>> >from another notifier anyway. Could you please test it? >>>> >>>> >>> >>> Hi, Alexey, >>> >>> Nice to see your comment. Let me show what I got fist. >>> >>> Generally, when kernel enumerate on the pci device, following functions will >>> be invoked. >>> >>> pci_device_add >>> pcibios_setup_bus_device >>> ... >>> set_iommu_table_base_and_group >>> device_add >>> ... >>> tce_iommu_bus_notifier >>> pcibios_fixp_bus >>> pcibios_add_pci_devices >>> ... >>> pcibios_setup_bus_devices >>> >>> >From the call flow, we see for a normall pci device, the >>> pcibios_setup_bus_device() will be invoked twice. >> >> >> tce_iommu_bus_notifier should not be called for devices during boot-time >> PCI discovery as the discovery is done from subsys_initcall handler and >> tce_iommu_bus_notifier is registered as subsys_initcall_sync. Are you sure >> this is happening? You should see warnings as for PF's EEH but you do not >> say that. >> > > Let me make it clearer. I list the call flow for general purpose to show the > sequence of the call flow. > > The tce_iommu_bus_notifier is not invoked at the boot time. And none of them > do real thing at boot time. > > I don't understand your last sentence. I see warning and error during EEH > hotplug. If necessary, I will add this in the commit log. > >> >>> At the bootup time, none of them succeed to setup the dma, since the PE is >>> not >>> assigned or the tbl is not set. The iommu tbl and group is setup in >>> pnv_pci_ioda_setup_DMA(). >>> >>> This call flow maintains the same when EEH error happens on Bus PE, while >>> the >>> behavior is a little different. >>> >>> pci_device_add >>> pcibios_setup_bus_device >>> ... >>> set_iommu_table_base_and_group <- fail, kobj->sd is not >>> initialized >> >> >> Sorry, what is uninitialized? The only kobj here is the one in iommu_group >> and it must have been taken care of before adding a device. > > pci_dev->dev->kobj->sd. > > I have explained this in previous discussion. This kobj->sd is initialized in > device_add(). > >> >> >>> device_add >>> ... >>> tce_iommu_bus_notifier <- succeed >>> pcibios_fixp_bus >>> pcibios_add_pci_devices >>> ... >>> pcibios_setup_bus_devices <- warning, re-attach >> >> >> This is why I am suggesting getting rid of tce_iommu_bus_notifier - we will >> avoid the warning. > > Then how about the first time's error?
What do you call "first time error" here? >>> While this call flow will change a little on a VF. For a VF, >>> pcibios_fixp_bus() will not be invoked. Current behavior is this. >> >> >> You meant pcibios_fixup_bus? I would expect it to get called (from >> pci_rescan_bus() or something like that?) and this seems to be the problem >> here. > > When EEH happens and hotplug the pci bus, we need to do the pci_scan_bridge() > which will do the pcibios_fixup_bus(). Are you talking now about EEH on PF (physical function) or EEH on VF (virtual function)? Are you calling pci_scan_bridge() > So you suggest to remove it? This is the generic code. I suggest removing tce_iommu_bus_notifier only. It must go. It was my mistake at the first place. >> How are VFs added in terms of code flow? Is there any git tree to look at? >> > > VF add code flow is a generic code in drivers/pci/iov.c, virtfn_add(). virtfn_add -> pci_device_add -> pcibios_add_device -> pcibios_setup_device -> ppc_md.pci_dma_dev_setup -> pnv_pci_dma_dev_setup -> pnv_pci_ioda_dma_dev_setup -> set_iommu_table_base. What part of this is missing? > >> >> >>> pci_device_add >>> pcibios_setup_bus_device >>> ... >>> set_iommu_table_base_and_group <- fail, kobj->sd is not >>> initialized >>> device_add >>> ... >>> tce_iommu_bus_notifier <- succeed >>> >>> And if an EEH error happens just on a VF, I believe the same call flow >>> should >>> go for recovery. (This is not set down, still under discussion with Gavin.) >>> >>> My conclusion is: >>> 1. remove the tce_iommu_bus_notifier completely will make the VF not work. >>> So I choose to revert the code and attach make the iommu group attachment >>> just happens in one place. >>> >>> BTW, I know my patch is not a perfect one. For a PF, the tbl will still be >>> set >>> twice. I am not sure why we need to invoke pcibios_setup_device() twice on a >>> PF, maybe some platform need to fixup some thing after the pci_bus is added. >>> So I don't remove one of them to solve the problem. >>> >>> If you have a better idea, I am glad to take it. -- Alexey _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
