skiboot v6.3-rc3 was released on Thursday May 2nd 2019. It is the third release candidate of skiboot 6.3, which will become the new stable release of skiboot following the 6.2 release, first released December 14th 2018.

Skiboot 6.3 will mark the basis for op-build v2.3. I expect to tag the final skiboot 6.3 in the next week (I also predicted this last time, so take my predictions with a large amount of sodium).

skiboot v6.3-rc3 contains all bug fixes as of skiboot-6.0.19, and skiboot-6.2.3 (the currently maintained stable releases).

For how the skiboot stable releases work, see Skiboot stable tree rules and releases for details.

Over skiboot-6.3-rc2, we have the following changes:

  • Expose PNOR Flash partitions to host MTD driver via devicetree

    This makes it possible for the host to directly address each partition without requiring each application to directly parse the FFS headers. This has been in use for some time already to allow BOOTKERNFW partition updates from the host.

    All partitions except BOOTKERNFW are marked readonly.

    The BOOTKERNFW partition is currently exclusively used by the TalosII platform

  • Write boot progress to LPC port 80h

    This is an adaptation of what we currently do for op_display() on FSP machines, inventing an encoding for what we can write into the single byte at LPC port 80h.

    Port 80h is often used on x86 systems to indicate boot progress/status and dates back a decent amount of time. Since a byte isn’t exactly very expressive for everything that can go on (and wrong) during boot, it’s all about compromise.

    Some systems (such as Zaius/Barreleye G2) have a physical dual 7 segment display that display these codes. So far, this has only been driven by hostboot (see hostboot commit 90ec2e65314c).

  • Write boot progress to LPC ports 81 and 82

    There’s a thought to write more extensive boot progress codes to LPC ports 81 and 82 to supplement/replace any reliance on port 80.

    We want to still emit port 80 for platforms like Zaius and Barreleye that have the physical display. Ports 81 and 82 can be monitored by a BMC though.

  • Copy and convert Romulus descriptors to Talos

    Talos II has some hardware differences from Romulus, therefore we cannot guarantee Talos II == Romulus in skiboot. Copy and slightly modify the Romulus files for Talos II.

  • npu2: Disable Probe-to-Invalid-Return-Modified-or-Owned snarfing by default

    V100 GPUs are known to violate NVLink2 protocol in some cases (one is when memory was accessed by the CPU and they by GPU using so called block linear mapping) and issue double probes to NPU which can cope with this problem only if CONFIG_ENABLE_SNARF_CPM (“disable/enable Probe.I.MO snarfing a cp_m”) is not set in the CQ_SM Misc Config register #0. If the bit is set (which is the case today), NPU issues the machine check stop.

    The snarfing feature is designed to detect 2 probes in flight and combine them into one.

    This adds a new “opal-npu2-snarf-cpm” nvram variable which controls CONFIG_ENABLE_SNARF_CPM for all NVLinks to prevent the machine check stop from happening.

    This disables snarfing by default as otherwise a broken GPU driver can crash the entire box even when a GPU is passed through to a guest. This provides a dial to allow regression tests (might be useful for a bare metal). To enable snarfing, the user needs to run:

    sudo nvram -p ibm,skiboot --update-config opal-npu2-snarf-cpm=enable

    and reboot the host system.

  • hw/npu2: Show name of opencapi error interrupts

  • core/pci: Use PHB io-base-location by default for PHB slots

    On witherspoon only the GPU slots and the three pluggable PCI slots (SLOT0, 1, 2) have platform defined slot names. For builtin devices such as the SATA controller or the PLX switch that fans out to the GPU slots we have no location codes which some people consider an issue.

    This patch address the problem by making the ibm,slot-location-code for the root port device default to the ibm,io-base-location-code which is typically the location code for the system itself.



    The PHB node, and the root complex nodes have a loc code of the processor they are attached to, while the usb-xhci device under the root port has a location code of the system itself.

  • hw/phb4: Read ibm,loc-code from PBCQ node

    On P9 the PBCQs are subdivided by stacks which implement the PCI Express logic. When phb4 was forked from phb3 most of the properties that were in the pbcq node moved into the stack node, but ibm,loc-code was not one of them. This patch fixes the phb4 init sequence to read the base location code from the PBCQ node (parent of the stack node) rather than the stack node itself.

  • hw/xscom: add missing P9P chip name

  • asm/head: balance branches to avoid link stack predictor mispredicts

    The Linux wrapper for OPAL call and return is arranged like this:

        mflr   r0
        std    r0,PPC_STK_LROFF(r1)
        LOAD_REG_ADDR(r11, opal_return)
        mtlr   r11
        hrfid  -> OPAL
        ld     r0,PPC_STK_LROFF(r1)
        mtlr   r0

    When skiboot returns to Linux, it branches to LR (i.e., opal_return) with a blr. This unbalances the link stack predictor and will cause mispredicts back up the return stack.

  • external/mambo: also invoke readline for the non-autorun case

  • asm/head.S: set POWER9 radix HID bit at entry

    When running in virtual memory mode, the radix MMU hid bit should not be changed, so set this in the initial boot SPR setup.

    As a side effect, fast reboot also has HID0:RADIX bit set by the shared spr init, so no need for an explicit call.

  • opal-prd: Fix memory leak in is-fsp-system check

  • opal-prd: Check malloc return value

  • hw/phb4: Squash the IO bridge window

    The PCI-PCI bridge spec says that bridges that implement an IO window should hardcode the IO base and limit registers to zero. Unfortunately, these registers only define the upper bits of the IO window and the low bits are assumed to be 0 for the base and 1 for the limit address. As a result, setting both to zero can be mis-interpreted as a 4K IO window.

    This patch fixes the problem the same way PHB3 does. It sets the IO base and limit values to 0xf000 and 0x1000 respectively which most software interprets as a disabled window.

    lspci before patch:

    0000:00:00.0 PCI bridge: IBM Device 04c1 (prog-if 00 [Normal decode])
            I/O behind bridge: 00000000-00000fff

    lspci after patch:

    0000:00:00.0 PCI bridge: IBM Device 04c1 (prog-if 00 [Normal decode])
            I/O behind bridge: None
  • build: link with –orphan-handling=warn

    The linker can warn when the linker script does not explicitly place all sections. These orphan sections are placed according to heuristics, which may not always be desirable. Enable this warning.

  • build: -fno-asynchronous-unwind-tables

    skiboot does not use unwind tables, this option saves about 100kB, mostly from .text.

  • hw/xscom: Enable sw xstop by default on p9

    This was disabled at some point during bringup to make life easier for the lab folks trying to debug NVLink issues. This hack really should have never made it out into the wild though, so we now have the following situation occuring in the field:

    1. A bad happens

    2. The host kernel recieves an unrecoverable HMI and calls into OPAL to request a platform reboot.

    3. OPAL rejects the reboot attempt and returns to the kernel with OPAL_PARAMETER.

    4. Kernel panics and attempts to kexec into a kdump kernel.

    A side effect of the HMI seems to be CPUs becoming stuck which results in the initialisation of the kdump kernel taking a extremely long time (6+ hours). It’s also been observed that after performing a dump the kdump kernel then crashes itself because OPAL has ended up in a bad state as a side effect of the HMI.

    All up, it’s not very good so re-enable the software checkstop by default. If people still want to turn it off they can using the nvram override.

  • opal/hmi: Initialize the hmi event with old value of TFMR.

    Do this before we fix TFAC errors. Otherwise the event at host console shows no thread error reported in TFMR register.

    Without this patch the console event show TFMR with no thread error: (DEC parity error TFMR[59] injection)

    [   53.737572] Severe Hypervisor Maintenance interrupt [Recovered]
    [   53.737596]  Error detail: Timer facility experienced an error
    [   53.737611]  HMER: 0840000000000000
    [   53.737621]  TFMR: 3212000870e04000

    After this patch it shows old TFMR value on host console:

    [ 2302.267271] Severe Hypervisor Maintenance interrupt [Recovered]
    [ 2302.267305]  Error detail: Timer facility experienced an error
    [ 2302.267320]  HMER: 0840000000000000
    [ 2302.267330]  TFMR: 3212000870e14010