On Wed, Jun 12, 2013 at 7:45 AM, Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx> wrote: > On Tue, Jun 11, 2013 at 05:17:45PM +0100, George Dunlap wrote: >> On 06/11/2013 05:08 PM, konrad wilk wrote: >> > >> >On 6/11/2013 11:36 AM, George Dunlap wrote: >> >>On 06/10/2013 10:06 PM, Konrad Rzeszutek Wilk wrote: >> >>>There are two tool-stack that can instruct the Xen PCI frontend >> >>>and backend to change states: 'xm' (Python code with a daemon), >> >>>and 'xl' (C library - does not keep state changes). >> >>> >> >>>With the 'xm', the path to disconnect a PCI device (xm pci-detach >> >>><guest> <BDF>)is: >> >>> >> >>>4(Connected)->7(Reconfiguring*)-> 8(Reconfigured)-> >> >>>4(Connected)->5(Closing*). >> >>> >> >>>The * is for states that the tool-stack sets. For 'xl', it is similar: >> >>> >> >>>4(Connected)->7(Reconfiguring*)-> 8(Reconfigured)-> 4(Connected) >> >>> >> >>>Both of them also tear down the XenBus structure, so the backend >> >>>state ends up going in the 3(Initialised) and calls >> >>>pcifront_xenbus_remove. >> >> >> >>So I looked a little bit into this; there are actually two different >> >>states that happen as part of this handshake. In order to disonnect a >> >>*device*, xl signals using the *bus* state, like this: >> >>* Wait for the *bus* to be in state 4(Connected) >> >>* Set the *device* state to 5(Closing) >> >>* Set the *bus* state to 7(Reconfiguring) >> >>* Wait for the *bus* state to return to 4(Connected) >> >> >> >>So are all of these states you see the *bus* state? And why would you >> >>disconnect the whole pci bus if you're only removing one device? >> > >> >Correct. The stats I enumerated are *bus* states. Not per-device states. >> >I presume (and I hadn't checked xm) that Xend has some logic to only >> >disconnect the bus if all of the PCI devices have been disconnected. In >> >'xl' it does not do that. >> > >> >The testing I did was just with one PCI device. >> >> Ah, OK -- I see now. The problem is that the code in the Linux side >> didn't know about the whole "4->7->8->4" thing to unplug a device. >> In all likelihood, if you had used xm with two devices (so that the >> bus didn't get disconnected), then you would have run across the >> same error. >> >> So at least part of the problem *is* a bug in Linux. > > Good! Bjorn, would you be OK Ack-ing the patch I sent (attached here > for reference) or putting it in your queue for Linus? > > My plan would be to send it to Linus in the 3.11 merge window. Sure; this is your baby :) Why don't you handle it via your tree, since it's more related to xen than any PCI core stuff. Acked-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx> -- 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
