skiboot 5.9.5 Release Notes

Signed-off-by: Stewart Smith <[email protected]>

doc/release-notes/skiboot-5.9.5.rst

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+.. _skiboot-5.9.5:
+
+=============
+skiboot-5.9.5
+=============
+
+skiboot 5.9.5 was released on Wednesday December 13th, 2017. It replaces
+:ref:`skiboot-5.9.4` as the current stable release in the 5.9.x series.
+
+Over :ref:`skiboot-5.9.4`, we have a few bug fixes, they are:
+
+- Fix *extremely* rare race in timer code.
+- xive: Ensure VC informational FIRs are masked
+
+  Some HostBoot versions leave those as checkstop, they are harmless
+  and can sometimes occur during normal operations.
+- xive: Fix occasional VC checkstops in xive_reset
+
+  The current workaround for the scrub bug described in
+  __xive_cache_scrub() has an issue in that it can leave
+  dirty invalid entries in the cache.
+
+  When cleaning up EQs or VPs during reset, if we then
+  remove the underlying indirect page for these entries,
+  the XIVE will checkstop when trying to flush them out
+  of the cache.
+
+  This replaces the existing workaround with a new pair of
+  workarounds for VPs and EQs:
+
+  - The VP one does the dummy watch on another entry than
+    the one we scrubbed (which does the job of pushing old
+    stores out) using an entry that is known to be backed by
+    a permanent indirect page.
+  - The EQ one switches to a more efficient workaround
+    which consists of doing a non-side-effect ESB load from
+    the EQ's ESe control bits.
+- io: Add load_wait() helper
+
+  This uses the standard form twi/isync pair to ensure a load
+  is consumed by the core before continuing. This can be necessary
+  under some circumstances for example when having the following
+  sequence:
+
+  - Store reg A
+  - Load reg A (ensure above store pushed out)
+  - delay loop
+  - Store reg A
+
+  IE, a mandatory delay between 2 stores. In theory the first store
+  is only guaranteed to rach the device after the load from the same
+  location has completed. However the processor will start executing
+  the delay loop without waiting for the return value from the load.
+
+  This construct enforces that the delay loop isn't executed until
+  the load value has been returned.
+- xive: Do not return a trigger page for an escalation interrupt
+
+  This is bogus, we don't support them. (Thankfully the callers
+  didn't actually try to use this on escalation interrupts).
+- xive: Mark a freed IRQ's IVE as valid and masked
+
+  Removing the valid bit means a FIR will trip if it's accessed
+  inadvertently. Under some circumstances, the XIVE will speculatively
+  access an IVE for a masked interrupt and trip it. So make sure that
+  freed entries are still marked valid (but masked).
+- hw/nx: Fix NX BAR assignments
+
+  The NX rng BAR is used by each core to source random numbers for the
+  DARN instruction. Currently we configure each core to use the NX rng of
+  the chip that it exists on. Unfortunately, the NX can be deconfigured by
+  hostboot and in this case we need to use the NX of a different chip.
+
+  This patch moves the BAR assignments for the NX into the normal nx-rng
+  init path. This lets us check if the normal (chip local) NX is active
+  when configuring which NX a core should use so that we can fallback
+  gracefully.