skiboot 5.9-rc2 release notesv5.9-rc2

Signed-off-by: Stewart Smith <stewart@linux.vnet.ibm.com>

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+.. _skiboot-5.9-rc2:
+
+skiboot-5.9-rc2
+===============
+
+skiboot v5.9-rc2 was released on Monday October 16th 2017. It is the second
+release candidate of skiboot 5.9, which will become the new stable release
+of skiboot following the 5.8 release, first released August 31st 2017.
+
+skiboot v5.9-rc2 contains all bug fixes as of :ref:`skiboot-5.4.8`
+and :ref:`skiboot-5.1.21` (the currently maintained stable releases). We
+do not currently expect to do any 5.8.x stable releases.
+
+For how the skiboot stable releases work, see :ref:`stable-rules` for details.
+
+The current plan is to cut the final 5.9 by October 17th, with skiboot 5.9
+being for all POWER8 and POWER9 platforms in op-build v1.20 (Due October 18th).
+This release will be targetted to early POWER9 systems.
+
+Over :ref:`skiboot-5.9-rc1`, we have the following changes:
+
+- opal-prd: Fix memory leak
+- hdata/i2c: update the list of known i2c devs
+
+  This updates the list of known i2c devices - as of HDAT spec v10.5e - so
+  that they can be properly identified during the hdat parsing.
+- hdata/i2c: log unknown i2c devices
+
+  An i2c device is unknown if either the i2c device list is outdated or
+  the device is marked as unknown (0xFF) in the hdat.
+
+- opal/cpu: Mark the core as bad while disabling threads of the core.
+
+  If any of the core fails to sync its TB during chipTOD initialization,
+  all the threads of that core are disabled. But this does not make
+  linux kernel to ignore the core/cpus. It crashes while bringing them up
+  with below backtrace: ::
+
+    [   38.883898] kexec_core: Starting new kernel
+    cpu 0x0: Vector: 300 (Data Access) at [c0000003f277b730]
+        pc: c0000000001b9890: internal_create_group+0x30/0x304
+        lr: c0000000001b9880: internal_create_group+0x20/0x304
+        sp: c0000003f277b9b0
+       msr: 900000000280b033
+       dar: 40
+     dsisr: 40000000
+      current = 0xc0000003f9f41000
+      paca    = 0xc00000000fe00000   softe: 0        irq_happened: 0x01
+        pid   = 2572, comm = kexec
+    Linux version 4.13.2-openpower1 (jenkins@p89) (gcc version 6.4.0 (Buildroot 2017.08-00006-g319c6e1)) #1 SMP Wed Sep 20 05:42:11 UTC 2017
+    enter ? for help
+    [c0000003f277b9b0] c0000000008a8780 (unreliable)
+    [c0000003f277ba50] c00000000041c3ac topology_add_dev+0x2c/0x40
+    [c0000003f277ba70] c00000000006b078 cpuhp_invoke_callback+0x88/0x170
+    [c0000003f277bac0] c00000000006b22c cpuhp_up_callbacks+0x54/0xb8
+    [c0000003f277bb10] c00000000006bc68 cpu_up+0x11c/0x168
+    [c0000003f277bbc0] c00000000002f0e0 default_machine_kexec+0x1fc/0x274
+    [c0000003f277bc50] c00000000002e2d8 machine_kexec+0x50/0x58
+    [c0000003f277bc70] c0000000000de4e8 kernel_kexec+0x98/0xb4
+    [c0000003f277bce0] c00000000008b0f0 SyS_reboot+0x1c8/0x1f4
+    [c0000003f277be30] c00000000000b118 system_call+0x58/0x6c
+
+- hw/imc: pause microcode at boot
+
+  IMC nest counters has both in-band (ucode access) and out of
+  band access to it. Since not all nest counter configurations
+  are supported by ucode, out of band tools are used to characterize
+  other configuration.
+
+  So it is prefer to pause the nest microcode at boot to aid the
+  nest out of band tools. If the ucode not paused and OS does not
+  have IMC driver support, then out to band tools will race with
+  ucode and end up getting undesirable values. Patch to check and
+  pause the ucode at boot.
+
+  OPAL provides APIs to control IMC counters. OPAL_IMC_COUNTERS_INIT
+  is used to initialize these counters at boot. OPAL_IMC_COUNTERS_START
+  and OPAL_IMC_COUNTERS_STOP API calls should be used to start and pause
+  these IMC engines. `doc/opal-api/opal-imc-counters.rst` details the
+  OPAL APIs and their usage.
+- xive: Fix VP free block group mode false-positive parameter check
+
+  The check to ensure the buddy allocation idx is aligned to its
+  allocation order was not taking into account the allocation split.
+  This would result in opal_xive_free_vp_block failures despite
+  giving the same value as returned by opal_xive_alloc_vp_block.
+
+  E.g., starting then stopping 4 KVM guests gives the following pattern
+  in the host: ::
+
+      opal_xive_alloc_vp_block(5)=0x45000020
+      opal_xive_alloc_vp_block(5)=0x45000040
+      opal_xive_alloc_vp_block(5)=0x45000060
+      opal_xive_alloc_vp_block(5)=0x45000080
+      opal_xive_free_vp_block(0x45000020)=-1
+      opal_xive_free_vp_block(0x45000040)=0
+      opal_xive_free_vp_block(0x45000060)=-1
+      opal_xive_free_vp_block(0x45000080)=0
+- hw/p8-i2c: Fix deadlock in p9_i2c_bus_owner_change
+
+  When debugging a system where Linux was taking soft lockup errors with
+  two CPUs stuck in OPAL:
+
+  ======================= ==============
+  CPU0                    CPU1
+  ======================= ==============
+  lock
+  p8_i2c_recover
+  opal_handle_interrupt
+                          sync_timer
+			  cancel_timer
+			  p9_i2c_bus_owner_change
+			  occ_p9_interrupt
+			  xive_source_interrupt
+			  opal_handle_interrupt
+  ======================= ==============
+
+  p8_i2c_recover() is a timer, and is stuck trying to take master->lock.
+  p9_i2c_bus_owner_change() has taken master->lock, but then is stuck waiting
+  for all timers to complete. We deadlock.
+
+  Fix this by using cancel_timer_async().
+
+- FSP/CONSOLE: Limit number of error logging
+
+  Commit c8a7535f (FSP/CONSOLE: Workaround for unresponsive ipmi daemon) added
+  error logging when buffer is full. In some corner cases kernel may call this
+  function multiple time and we may endup logging error again and again.
+
+  This patch fixes it by generating error log only once.
+
+- FSP/CONSOLE: Fix fsp_console_write_buffer_space() call
+
+  Kernel calls fsp_console_write_buffer_space() to check console buffer space
+  availability. If there is enough buffer space to write data, then kernel will
+  call fsp_console_write() to write actual data.
+
+  In some extreme corner cases (like one explained in commit c8a7535f)
+  console becomes full and this function returns 0 to kernel (or space available
+  in console buffer < next incoming data size). Kernel will continue retrying
+  until it gets enough space. So we will start seeing RCU stalls.
+
+  This patch keeps track of previous available space. If previous space is same
+  as current means not enough space in console buffer to write incoming data.
+  It may be due to very high console write operation and slow response from FSP
+  -OR- FSP has stopped processing data (ex: because of ipmi daemon died). At this
+  point we will start timer with timeout of SER_BUFFER_OUT_TIMEOUT (10 secs).
+  If situation is not improved within 10 seconds means something went bad. Lets
+  return OPAL_RESOURCE so that kernel can drop console write and continue.
+- FSP/CONSOLE: Close SOL session during R/R
+
+  Presently we are not closing SOL and FW console sessions during R/R. Host will
+  continue to write to SOL buffer during FSP R/R. If there is heavy console write
+  operation happening during FSP R/R (like running `top` command inside console),
+  then at some point console buffer becomes full. fsp_console_write_buffer_space()
+  returns 0 (or less than required space to write data) to host. While one thread
+  is busy writing to console, if some other threads tries to write data to console
+  we may see RCU stalls (like below) in kernel. ::
+
+    [ 2082.828363] INFO: rcu_sched detected stalls on CPUs/tasks: { 32} (detected by 16, t=6002 jiffies, g=23154, c=23153, q=254769)
+    [ 2082.828365] Task dump for CPU 32:
+    [ 2082.828368] kworker/32:3    R  running task        0  4637      2 0x00000884
+    [ 2082.828375] Workqueue: events dump_work_fn
+    [ 2082.828376] Call Trace:
+    [ 2082.828382] [c000000f1633fa00] [c00000000013b6b0] console_unlock+0x570/0x600 (unreliable)
+    [ 2082.828384] [c000000f1633fae0] [c00000000013ba34] vprintk_emit+0x2f4/0x5c0
+    [ 2082.828389] [c000000f1633fb60] [c00000000099e644] printk+0x84/0x98
+    [ 2082.828391] [c000000f1633fb90] [c0000000000851a8] dump_work_fn+0x238/0x250
+    [ 2082.828394] [c000000f1633fc60] [c0000000000ecb98] process_one_work+0x198/0x4b0
+    [ 2082.828396] [c000000f1633fcf0] [c0000000000ed3dc] worker_thread+0x18c/0x5a0
+    [ 2082.828399] [c000000f1633fd80] [c0000000000f4650] kthread+0x110/0x130
+    [ 2082.828403] [c000000f1633fe30] [c000000000009674] ret_from_kernel_thread+0x5c/0x68
+
+  Hence lets close SOL (and FW console) during FSP R/R.
+- FSP/CONSOLE: Do not associate unavailable console
+
+  Presently OPAL sends associate/unassociate MBOX command for all
+  FSP serial console (like below OPAL message). We have to check
+  console is available or not before sending this message. ::
+
+    [ 5013.227994012,7] FSP: Reassociating HVSI console 1
+    [ 5013.227997540,7] FSP: Reassociating HVSI console 2
+- FSP: Disable PSI link whenever FSP tells OPAL about impending R/R
+
+  Commit 42d5d047 fixed scenario where DPO has been initiated, but FSP went
+  into reset before the CEC power down came in. But this is generic issue
+  that can happen in normal shutdown path as well.
+
+  Hence disable PSI link as soon as we detect FSP impending R/R.
+
+- fsp: return OPAL_BUSY_EVENT on failure sending FSP_CMD_POWERDOWN_NORM
+  Also, return OPAL_BUSY_EVENT on failure sending FSP_CMD_REBOOT / DEEP_REBOOT.
+
+  We had a race condition between FSP Reset/Reload and powering down
+  the system from the host:
+
+  Roughly:
+
+  == ======================== ==========================================================
+  #  FSP                      Host
+  == ======================== ==========================================================
+  1  Power on
+  2                           Power on
+  3  (inject EPOW)
+  4  (trigger FSP R/R)
+  5                           Processes EPOW event, starts shutting down
+  6                           calls OPAL_CEC_POWER_DOWN
+  7  (is still in R/R)
+  8                           gets OPAL_INTERNAL_ERROR, spins in opal_poll_events
+  9  (FSP comes back)
+  10                          spinning in opal_poll_events
+  11 (thinks host is running)
+  == ======================== ==========================================================
+
+  The call to OPAL_CEC_POWER_DOWN is only made once as the reset/reload
+  error path for fsp_sync_msg() is to return -1, which means we give
+  the OS OPAL_INTERNAL_ERROR, which is fine, except that our own API
+  docs give us the opportunity to return OPAL_BUSY when trying again
+  later may be successful, and we're ambiguous as to if you should retry
+  on OPAL_INTERNAL_ERROR.
+
+  For reference, the linux code looks like this: ::
+
+    static void __noreturn pnv_power_off(void)
+    {
+            long rc = OPAL_BUSY;
+    
+            pnv_prepare_going_down();
+    
+            while (rc == OPAL_BUSY || rc == OPAL_BUSY_EVENT) {
+                    rc = opal_cec_power_down(0);
+                    if (rc == OPAL_BUSY_EVENT)
+                            opal_poll_events(NULL);
+                    else
+                            mdelay(10);
+            }
+            for (;;)
+                    opal_poll_events(NULL);
+    }
+
+  Which means that *practically* our only option is to return OPAL_BUSY
+  or OPAL_BUSY_EVENT.
+
+  We choose OPAL_BUSY_EVENT for FSP systems as we do want to ensure we're
+  running pollers to communicate with the FSP and do the final bits of
+  Reset/Reload handling before we power off the system.