XHCI page fault under skylake

[kallisti5]

This issue generally occurs when booting from a USB 3 flash drive.

_ZN4XHCIC2EP8pci_infoP5Stack() -> XHCI::XHCI(pci_info*, Stack*)
_ZN4XHCI5AddToEP5Stack ()      -> XHCI::AddTo(Stack*)
_ZN5StackC1Ev ()               -> Stack::Stack()

This line seems to be a core issue in syslog:

usb xhci -1: using message signaled interrupts
usb xhci -1: stating XHCI host controller
usb hub 2: hub supports more ports than we do (18 vs. 16)
usb xhci -1: successfully started the controller

[kallisti5]

(at boot from USB 2.0 stick plugged into USB 3.1 socket. hrev50452 x86_64)

[kallisti5]

Tested hrev50454, issue still exists w/no changes.

[korli]

Weird, it is as if there were a second XHCI controller to initialize (the first is started, an allocation for a second controller is being done while KDLed).

[kallisti5]

Only one USB controller via linux:

$ sudo lspci -s 00:14.0 -nnn -vv
00:14.0 USB controller [0c03]: Intel Corporation Sunrise Point-LP USB 3.0 xHCI Controller [8086:9d2f] (rev 21) (prog-if 30 [XHCI])
	Subsystem: Dell Sunrise Point-LP USB 3.0 xHCI Controller [1028:0704]
	Control: I/O- Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx+
	Status: Cap+ 66MHz- UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
	Latency: 0
	Interrupt: pin A routed to IRQ 122
	Region 0: Memory at dc210000 (64-bit, non-prefetchable) [size=64K]
	Capabilities: [70] Power Management version 2
		Flags: PMEClk- DSI- D1- D2- AuxCurrent=375mA PME(D0-,D1-,D2-,D3hot+,D3cold+)
		Status: D0 NoSoftRst+ PME-Enable- DSel=0 DScale=0 PME-
	Capabilities: [80] MSI: Enable+ Count=1/8 Maskable- 64bit+
		Address: 00000000fee00238  Data: 0000
	Kernel driver in use: xhci_hcd

lsusb:

$ lsusb
Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 001 Device 004: ID 0bda:5682 Realtek Semiconductor Corp. 
Bus 001 Device 003: ID 04f3:20d0 Elan Microelectronics Corp. 
Bus 001 Device 002: ID 8087:0a2a Intel Corp. 
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

dmesg:

$ dmesg | grep -i xhci
[    1.195032] xhci_hcd 0000:00:14.0: xHCI Host Controller
[    1.195037] xhci_hcd 0000:00:14.0: new USB bus registered, assigned bus number 1
[    1.196210] xhci_hcd 0000:00:14.0: hcc params 0x200077c1 hci version 0x100 quirks 0x00109810
[    1.196215] xhci_hcd 0000:00:14.0: cache line size of 64 is not supported
[    1.196299] usb usb1: Product: xHCI Host Controller
[    1.196301] usb usb1: Manufacturer: Linux 4.4.0-31-generic xhci-hcd
[    1.203786] xhci_hcd 0000:00:14.0: xHCI Host Controller
[    1.203790] xhci_hcd 0000:00:14.0: new USB bus registered, assigned bus number 2
[    1.203817] usb usb2: Product: xHCI Host Controller
[    1.203819] usb usb2: Manufacturer: Linux 4.4.0-31-generic xhci-hcd
[    1.568146] usb 1-3: new full-speed USB device number 2 using xhci_hcd
[    1.920337] usb 1-4: new full-speed USB device number 3 using xhci_hcd
[    2.272169] usb 1-5: new high-speed USB device number 4 using xhci_hcd

[kallisti5]

interestingly:

kallisti5@ares ~ :) $ cat /sys/bus/usb/devices/usb1/product 
xHCI Host Controller
kallisti5@ares ~ :) $ cat /sys/bus/usb/devices/usb2/product 
xHCI Host Controller

 lsusb -tv
/:  Bus 02.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/6p, 5000M
/:  Bus 01.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/12p, 480M
    |__ Port 3: Dev 2, If 0, Class=Wireless, Driver=btusb, 12M
    |__ Port 3: Dev 2, If 1, Class=Wireless, Driver=btusb, 12M
    |__ Port 4: Dev 3, If 0, Class=Human Interface Device, Driver=usbhid, 12M
    |__ Port 5: Dev 4, If 0, Class=Video, Driver=uvcvideo, 480M
    |__ Port 5: Dev 4, If 1, Class=Video, Driver=uvcvideo, 480M

[korli]

Just a guess, it could be that the USB 2.0 stick comes in the last port of the hub, and because we use then the next out of bound index ​here. You could try to increase the value ​USB_MAX_PORT_COUNT to 32 for instance, and see what happens. (the lsusb output doesn't list the usb2 stick, so it's not clear what happens).

[kallisti5]

The logs not showing that error already had the max USB hub count bumped to 24. Same error appeared (minus the error about 16 vs 18)

[kallisti5]

bus 02 appears to be the USB C port and everything external. (USB 3.1) Bus 01 seems to be an internal bus operating at USB 2.0 speeds.

So this looks like a USB host controller that supports more than one bus? I wonder if EHCI did that.

[korli]

Replying to kallisti5:

So this looks like a USB host controller that supports more than one bus? I wonder if EHCI did that.

No, the XHCI Linux driver chooses to expose two root hubs (2.0 and 3.x), each port is present on both hubs. If a USB2 device is connected, it appears on the 2.0 root hub, otherwise on the 3.x root hub.

It might help if you could try with TRACE_USB enabled.

[kallisti5]

backtrace from USB 3 flash drive

[kallisti5]

XHCI Log output with tracing enabled

[kallisti5]

KDL BT - hrev50621, x86_64, Sky Lake, USB 3.0

[kallisti5]

syslog - hrev50621, x86_64, Sky Lake, USB 3.0