skiboot-6.3.2

skiboot 6.3.2 was released on Monday July 1st, 2019. It replaces skiboot-6.3.1 as the current stable release in the 6.3.x series.

It is recommended that 6.3.2 be used instead of 6.3.1 version due to the bug fixes it contains.

Bug fixes included in this release are:

  • npu2: Purge cache when resetting a GPU

    After putting all a GPU’s links in reset, do a cache purge in case we have CPU cache lines belonging to the now-unaccessible GPU memory.

  • npu2: Reset NVLinks when resetting a GPU

    Resetting a V100 GPU brings its NVLinks down and if an NPU tries using those, an HMI occurs. We were lucky not to observe this as the bare metal does not normally reset a GPU and when passed through, GPUs are usually before NPUs in QEMU command line or Libvirt XML and because of that NPUs are naturally reset first. However simple change of the device order brings HMIs.

    This defines a bus control filter for a PCI slot with a GPU with NVLinks so when the host system issues secondary bus reset to the slot, it resets associated NVLinks.

  • hw/phb4: Assert Link Disable bit after ETU init

    The cursed RAID card in ozrom1 has a bug where it ignores PERST being asserted. The PCIe Base spec is a little vague about what happens while PERST is asserted, but it does clearly specify that when PERST is de-asserted the Link Training and Status State Machine (LTSSM) of a device should return to the initial state (Detect) defined in the spec and the link training process should restart.

    This bug was worked around in 9078f8268922 (“phb4: Delay training till after PERST is deasserted”) by setting the link disable bit at the start of the FRESET process and clearing it after PERST was de-asserted. Although this fixed the bug, the patch offered no explaination of why the fix worked.

    In b8b4c79d4419 (“hw/phb4: Factor out PERST control”) the link disable workaround was moved into phb4_assert_perst(). This is called always in the CRESET case, but a following patch resulted in assert_perst() not being called if phb4_freset() was entered following a CRESET since p->skip_perst was set in the CRESET handler. This is bad since a side-effect of the CRESET is that the Link Disable bit is cleared.

    This, combined with the RAID card ignoring PERST results in the PCIe link being trained by the PHB while we’re waiting out the 100ms ETU reset time. If we hack skiboot to print a DLP trace after returning from phb4_hw_init() we get:

    PHB#0001[0:1]: Initialization complete
PHB#0001[0:1]: TRACE:0x0000102101000000  0ms presence GEN1:x16:polling
PHB#0001[0:1]: TRACE:0x0000001101000000 23ms          GEN1:x16:detect
PHB#0001[0:1]: TRACE:0x0000102101000000 23ms presence GEN1:x16:polling
PHB#0001[0:1]: TRACE:0x0000183101000000 29ms training GEN1:x16:config
PHB#0001[0:1]: TRACE:0x00001c5881000000 30ms training GEN1:x08:recovery
PHB#0001[0:1]: TRACE:0x00001c5883000000 30ms training GEN3:x08:recovery
PHB#0001[0:1]: TRACE:0x0000144883000000 33ms presence GEN3:x08:L0
PHB#0001[0:1]: TRACE:0x0000154883000000 33ms trained  GEN3:x08:L0
PHB#0001[0:1]: CRESET: wait_time = 100
PHB#0001[0:1]: FRESET: Starts
PHB#0001[0:1]: FRESET: Prepare for link down
PHB#0001[0:1]: FRESET: Assert skipped
PHB#0001[0:1]: FRESET: Deassert
PHB#0001[0:1]: TRACE:0x0000154883000000  0ms trained  GEN3:x08:L0
PHB#0001[0:1]: TRACE: Reached target state
PHB#0001[0:1]: LINK: Start polling
PHB#0001[0:1]: LINK: Electrical link detected
PHB#0001[0:1]: LINK: Link is up
PHB#0001[0:1]: LINK: Went down waiting for stabilty
PHB#0001[0:1]: LINK: DLP train control: 0x0000105101000000
PHB#0001[0:1]: CRESET: Starts

    What has happened here is that the link is trained to 8x Gen3 33ms after we return from phb4_init_hw(), and before we’ve waitined to 100ms that we normally wait after re-initialising the ETU. When we “deassert” PERST later on in the FRESET handler the link in L0 (normal) state. At this point we try to read from the Vendor/Device ID register to verify that the link is stable and immediately get a PHB fence due to a PCIe Completion Timeout. Skiboot attempts to recover by doing another CRESET, but this will encounter the same issue.

    This patch fixes the problem by setting the Link Disable bit (by calling phb4_assert_perst()) immediately after we return from phb4_init_hw(). This prevents the link from being trained while PERST is asserted which seems to avoid the Completion Timeout. With the patch applied we get:

    PHB#0001[0:1]: Initialization complete
PHB#0001[0:1]: TRACE:0x0000102101000000  0ms presence GEN1:x16:polling
PHB#0001[0:1]: TRACE:0x0000001101000000 23ms          GEN1:x16:detect
PHB#0001[0:1]: TRACE:0x0000102101000000 23ms presence GEN1:x16:polling
PHB#0001[0:1]: TRACE:0x0000909101000000 29ms presence GEN1:x16:disabled
PHB#0001[0:1]: CRESET: wait_time = 100
PHB#0001[0:1]: FRESET: Starts
PHB#0001[0:1]: FRESET: Prepare for link down
PHB#0001[0:1]: FRESET: Assert skipped
PHB#0001[0:1]: FRESET: Deassert
PHB#0001[0:1]: TRACE:0x0000001101000000  0ms          GEN1:x16:detect
PHB#0001[0:1]: TRACE:0x0000102101000000  0ms presence GEN1:x16:polling
PHB#0001[0:1]: TRACE:0x0000001101000000 24ms          GEN1:x16:detect
PHB#0001[0:1]: TRACE:0x0000102101000000 36ms presence GEN1:x16:polling
PHB#0001[0:1]: TRACE:0x0000183101000000 97ms training GEN1:x16:config
PHB#0001[0:1]: TRACE:0x00001c5881000000 97ms training GEN1:x08:recovery
PHB#0001[0:1]: TRACE:0x00001c5883000000 97ms training GEN3:x08:recovery
PHB#0001[0:1]: TRACE:0x0000144883000000 99ms presence GEN3:x08:L0
PHB#0001[0:1]: TRACE: Reached target state
PHB#0001[0:1]: LINK: Start polling
PHB#0001[0:1]: LINK: Electrical link detected
PHB#0001[0:1]: LINK: Link is up
PHB#0001[0:1]: LINK: Link is stable
PHB#0001[0:1]: LINK: Card [9005:028c] Optimal Retry:disabled
PHB#0001[0:1]: LINK: Speed Train:GEN3 PHB:GEN4 DEV:GEN3
PHB#0001[0:1]: LINK: Width Train:x08 PHB:x08 DEV:x08
PHB#0001[0:1]: LINK: RX Errors Now:0 Max:8 Lane:0x0000

  • npu2: Reset PID wildcard and refcounter when mapped to LPID

    Since 105d80f85b “npu2: Use unfiltered mode in XTS tables” we do not register every PID in the XTS table so the table has one entry per LPID. Then we added a reference counter to keep track of the entry use when switching GPU between the host and guest systems (the “Fixes:” tag below).

    The POWERNV platform setup creates such entries and references them at the boot time when initializing IOMMUs and only removes it when a GPU is passed through to a guest. This creates a problem as POWERNV boots via kexec and no defererencing happens; the XTS table state remains undefined. So when the host kernel boots, skiboot thinks there are valid XTS entries and does not update the XTS table which breaks ATS.

    This adds the reference counter and the XTS entry reset when a GPU is assigned to LPID and we cannot rely on the kernel to clean that up.

  • hw/phb4: Use read/write_reg in assert_perst

    While the PHB is fenced we can’t use the MMIO interface to access PHB registers. While processing a complete reset we inject a PHB fence to isolate the PHB from the rest of the system because the PHB won’t respond to MMIOs from the rest of the system while being reset.

    We assert PERST after the fence has been erected which requires us to use the XSCOM indirect interface to access the PHB registers rather than the MMIO interface. Previously we did that when asserting PERST in the CRESET path. However in b8b4c79d4419 (“hw/phb4: Factor out PERST control”). This was re-written to use the raw in_be64() accessor. This means that CRESET would not be asserted in the reset path. On some Mellanox cards this would prevent them from re-loading their firmware when the system was fast-reset.

    This patch fixes the problem by replacing the raw {in|out}_be64() accessors with the phb4_{read|write}_reg() functions.

  • opal-prd: Fix prd message size issue

    If prd messages size is insufficient then read_prd_msg() call fails with below error. And caller is not reallocating sufficient buffer. Also its hard to guess the size.

    sample log:

    Mar 28 03:31:43 zz24p1 opal-prd: FW: error reading from firmware: alloc 32 rc -1: Invalid argument
Mar 28 03:31:43 zz24p1 opal-prd: FW: error reading from firmware: alloc 32 rc -1: Invalid argument
Mar 28 03:31:43 zz24p1 opal-prd: FW: error reading from firmware: alloc 32 rc -1: Invalid argument

    Lets use opal-msg-size device tree property to allocate memory for prd message.

  • npu2: Fix clearing the FIR bits

    FIR registers are SCOM-only so they cannot be accesses with the indirect write, and yet we use SCOM-based addresses for these; fix this.

  • opal-gard: Account for ECC size when clearing partition

    When ‘opal-gard clear all’ is run, it works by erasing the GUARD then using blockevel_smart_write() to write nothing to the partition. This second write call is needed because we rely on libflash to set the ECC bits appropriately when the partition contained ECCed data.

    The API for this is a little odd with the caller specifying how much actual data to write, and libflash writing size + size/8 bytes since there is one additional ECC byte for every eight bytes of data.

    We currently do not account for the extra space consumed by the ECC data in reset_partition() which is used to handle the ‘clear all’ command. Which results in the paritition following the GUARD partition being partially overwritten when the command is used. This patch fixes the problem by reducing the length we would normally write by the number of ECC bytes required.

  • nvram: Flag dangerous NVRAM options

    Most nvram options used by skiboot are just for debug or testing for regressions. They should never be used long term.

    We’ve hit a number of issues in testing and the field where nvram options have been set “temporarily” but haven’t been properly cleared after, resulting in crashes or real bugs being masked.

    This patch marks most nvram options used by skiboot as dangerous and prints a chicken to remind users of the problem.

  • devicetree: Don’t set path to dtc in makefile

    By setting the path we fail to build under buildroot which has it’s own set of host tools in PATH, but not at /usr/bin.

    Keep the variable so it can be set if need be but default to whatever ‘dtc’ is in the users path.