On 05/21/2013 02:49 PM, Michael S. Tsirkin wrote: > 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 >>>> <alexander.h.duyck@xxxxxxxxx> wrote: >>>>> On 05/14/2013 11:44 AM, Yinghai Lu wrote: >>>>>> On Tue, May 14, 2013 at 9:00 AM, Alexander Duyck >>>>>> <alexander.h.duyck@xxxxxxxxx> 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. > As I understand the issue, the problem is not a deadlock for Mellanox (At least with either your patch or mine applied), the issue is that the PF is not ready to handle VFs when pci_enable_sriov is called due to some firmware issues. Thanks, Alex -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
