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From: Hari Bathini <hbathini@linux.ibm.com>
To: linuxppc-dev <linuxppc-dev@ozlabs.org>
Cc: Ananth N Mavinakayanahalli <ananth@linux.ibm.com>,
	Mahesh J Salgaonkar <mahesh@linux.ibm.com>,
	Vasant Hegde <hegdevasant@linux.ibm.com>,
	Oliver <oohall@gmail.com>, Nicholas Piggin <npiggin@gmail.com>,
	Daniel Axtens <dja@axtens.net>
Subject: [PATCH v6 23/36] powerpc/fadump: Update documentation about OPAL platform support
Date: Wed, 11 Sep 2019 20:23:53 +0530
Message-ID: <156821361692.5656.11377757995827253404.stgit@hbathini.in.ibm.com> (raw)
In-Reply-To: <156821308145.5656.2233728784001623843.stgit@hbathini.in.ibm.com>

With FADump support now available on both pseries and OPAL platforms,
update FADump documentation with these details.

Signed-off-by: Hari Bathini <hbathini@linux.ibm.com>
---

Changes in v6:
  * Specific the firmware release versions that support MPIPL.


 Documentation/powerpc/firmware-assisted-dump.rst |  122 +++++++++++++---------
 1 file changed, 72 insertions(+), 50 deletions(-)

diff --git a/Documentation/powerpc/firmware-assisted-dump.rst b/Documentation/powerpc/firmware-assisted-dump.rst
index d912755..ab578ac 100644
--- a/Documentation/powerpc/firmware-assisted-dump.rst
+++ b/Documentation/powerpc/firmware-assisted-dump.rst
@@ -46,10 +46,9 @@ as follows:
    These registered sections of memory are reserved by the first
    kernel during early boot.
 
--  When a system crashes, the Power firmware will save
-   the low memory (boot memory of size larger of 5% of system RAM
-   or 256MB) of RAM to the previous registered region. It will
-   also save system registers, and hardware PTE's.
+-  When system crashes, the Power firmware will copy the registered
+   low memory regions (boot memory) from source to destination area.
+   It will also save hardware PTE's.
 
    NOTE:
          The term 'boot memory' means size of the low memory chunk
@@ -61,9 +60,9 @@ as follows:
          the default calculated size. Use this option if default
          boot memory size is not sufficient for second kernel to
          boot successfully. For syntax of crashkernel= parameter,
-         refer to Documentation/admin-guide/kdump/kdump.rst. If any offset is
-         provided in crashkernel= parameter, it will be ignored
-         as FADump uses a predefined offset to reserve memory
+         refer to Documentation/admin-guide/kdump/kdump.rst. If any
+         offset is provided in crashkernel= parameter, it will be
+         ignored as FADump uses a predefined offset to reserve memory
          for boot memory dump preservation in case of a crash.
 
 -  After the low memory (boot memory) area has been saved, the
@@ -71,8 +70,9 @@ as follows:
    *not* clear the RAM. It will then launch the bootloader, as
    normal.
 
--  The freshly booted kernel will notice that there is a new
-   node (ibm,dump-kernel) in the device tree, indicating that
+-  The freshly booted kernel will notice that there is a new node
+   (rtas/ibm,kernel-dump on pSeries or ibm,opal/dump/mpipl-boot
+   on OPAL platform) in the device tree, indicating that
    there is crash data available from a previous boot. During
    the early boot OS will reserve rest of the memory above
    boot memory size effectively booting with restricted memory
@@ -95,8 +95,11 @@ as follows:
      # echo 1 > /sys/kernel/fadump_release_mem
 
 Please note that the firmware-assisted dump feature
-is only available on Power6 and above systems with recent
-firmware versions.
+is only available on POWER6 and above systems on pSeries
+(PowerVM) platform and POWER9 and above systems with OP940
+or later firmware versions on PowerNV (OPAL) platform.
+Note that, OPAL firmware exports ibm,opal/dump node when
+FADump is supported on PowerNV platform.
 
 Implementation details:
 -----------------------
@@ -111,57 +114,76 @@ that are run. If there is dump data, then the
 /sys/kernel/fadump_release_mem file is created, and the reserved
 memory is held.
 
-If there is no waiting dump data, then only the memory required
-to hold CPU state, HPTE region, boot memory dump and elfcore
-header, is usually reserved at an offset greater than boot memory
-size (see Fig. 1). This area is *not* released: this region will
-be kept permanently reserved, so that it can act as a receptacle
-for a copy of the boot memory content in addition to CPU state
-and HPTE region, in the case a crash does occur. Since this reserved
-memory area is used only after the system crash, there is no point in
-blocking this significant chunk of memory from production kernel.
-Hence, the implementation uses the Linux kernel's Contiguous Memory
-Allocator (CMA) for memory reservation if CMA is configured for kernel.
-With CMA reservation this memory will be available for applications to
-use it, while kernel is prevented from using it. With this FADump will
-still be able to capture all of the kernel memory and most of the user
-space memory except the user pages that were present in CMA region::
+If there is no waiting dump data, then only the memory required to
+hold CPU state, HPTE region, boot memory dump, FADump header and
+elfcore header, is usually reserved at an offset greater than boot
+memory size (see Fig. 1). This area is *not* released: this region
+will be kept permanently reserved, so that it can act as a receptacle
+for a copy of the boot memory content in addition to CPU state and
+HPTE region, in the case a crash does occur.
+
+Since this reserved memory area is used only after the system crash,
+there is no point in blocking this significant chunk of memory from
+production kernel. Hence, the implementation uses the Linux kernel's
+Contiguous Memory Allocator (CMA) for memory reservation if CMA is
+configured for kernel. With CMA reservation this memory will be
+available for applications to use it, while kernel is prevented from
+using it. With this FADump will still be able to capture all of the
+kernel memory and most of the user space memory except the user pages
+that were present in CMA region::
 
   o Memory Reservation during first kernel
 
-  Low memory                                                Top of memory
-  0      boot memory size      |<--Reserved dump area --->|      |
-  |           |                | (Permanent Reservation)  |      |
-  V           V                |                          |      V
-  +-----------+----------/ /---+---+----+--------+---+----+------+
-  |           |                |CPU|HPTE|  DUMP  |HDR|ELF |      |
-  +-----------+----------/ /---+---+----+--------+---+----+------+
-        |                                   ^      ^
-        |                                   |      |
-        \                                   /      |
-         -----------------------------------     FADump Header
-          Boot memory content gets transferred   (meta area)
-          to reserved area by firmware at the
-          time of crash
+  Low memory                                                 Top of memory
+  0    boot memory size   |<--- Reserved dump area --->|       |
+  |           |           |    Permanent Reservation   |       |
+  V           V           |                            |       V
+  +-----------+-----/ /---+---+----+-------+-----+-----+----+--+
+  |           |           |///|////|  DUMP | HDR | ELF |////|  |
+  +-----------+-----/ /---+---+----+-------+-----+-----+----+--+
+        |                   ^    ^     ^      ^           ^
+        |                   |    |     |      |           |
+        \                  CPU  HPTE   /      |           |
+         ------------------------------       |           |
+      Boot memory content gets transferred    |           |
+      to reserved area by firmware at the     |           |
+      time of crash.                          |           |
+                                          FADump Header   |
+                                           (meta area)    |
+                                                          |
+                                                          |
+                      Metadata: This area holds a metadata struture whose
+                      address is registered with f/w and retrieved in the
+                      second kernel after crash, on platforms that support
+                      tags (OPAL). Having such structure with info needed
+                      to process the crashdump eases dump capture process.
 
                    Fig. 1
 
 
   o Memory Reservation during second kernel after crash
 
-  Low memory                                                Top of memory
-  0      boot memory size                                        |
-  |           |<----------- Crash preserved area --------------->|
-  V           V                |<-- Reserved dump area -->|      V
-  +-----------+----------/ /---+---+----+--------+---+----+------+
-  |           |                |CPU|HPTE|  DUMP  |HDR|ELF |      |
-  +-----------+----------/ /---+---+----+--------+---+----+------+
-        |                                              |
-        V                                              V
-   Used by second                                /proc/vmcore
+  Low memory                                              Top of memory
+  0      boot memory size                                      |
+  |           |<------------ Crash preserved area ------------>|
+  V           V           |<--- Reserved dump area --->|       |
+  +-----------+-----/ /---+---+----+-------+-----+-----+----+--+
+  |           |           |///|////|  DUMP | HDR | ELF |////|  |
+  +-----------+-----/ /---+---+----+-------+-----+-----+----+--+
+        |                                           |
+        V                                           V
+   Used by second                             /proc/vmcore
    kernel to boot
+
+        +---+
+        |///| -> Regions (CPU, HPTE & Metadata) marked like this in the above
+        +---+    figures are not always present. For example, OPAL platform
+                 does not have CPU & HPTE regions while Metadata region is
+                 not supported on pSeries currently.
+
                    Fig. 2
 
+
 Currently the dump will be copied from /proc/vmcore to a new file upon
 user intervention. The dump data available through /proc/vmcore will be
 in ELF format. Hence the existing kdump infrastructure (kdump scripts)


  parent reply index

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-11 14:45 [PATCH v6 00/36] Add FADump support on PowerNV platform Hari Bathini
2019-09-11 14:46 ` [PATCH v6 01/36] powerpc/fadump: move internal macros/definitions to a new header Hari Bathini
2019-09-19 10:25   ` Michael Ellerman
2019-09-11 14:46 ` [PATCH v6 02/36] powerpc/fadump: add helper functions Hari Bathini
2019-09-11 14:46 ` [PATCH v6 03/36] powerpc/fadump: declare helper functions in internal header file Hari Bathini
2019-09-11 14:47 ` [PATCH v6 04/36] powerpc/fadump: Improve fadump documentation Hari Bathini
2019-09-11 14:47 ` [PATCH v6 05/36] powerpc/fadump: use helper functions to reserve/release cpu notes buffer Hari Bathini
2019-09-11 14:48 ` [PATCH v6 06/36] pseries/fadump: move rtas specific definitions to platform code Hari Bathini
2019-09-11 14:48 ` [PATCH v6 07/36] pseries/fadump: introduce callbacks for platform specific operations Hari Bathini
2019-09-11 14:48 ` [PATCH v6 08/36] pseries/fadump: define RTAS register/un-register callback functions Hari Bathini
2019-09-11 14:49 ` [PATCH v6 09/36] pseries/fadump: add source info while displaying region contents Hari Bathini
2019-09-11 14:49 ` [PATCH v6 10/36] powerpc/fadump: release all the memory above boot memory size Hari Bathini
2019-09-11 14:49 ` [PATCH v6 11/36] pseries/fadump: move out platform specific support from generic code Hari Bathini
2019-09-11 14:49 ` [PATCH v6 12/36] powerpc/fadump: use FADump instead of fadump for how it is pronounced Hari Bathini
2019-09-11 14:50 ` [PATCH v6 13/36] opal: add MPIPL interface definitions Hari Bathini
2019-09-11 14:50 ` [PATCH v6 14/36] powernv/fadump: add fadump support on powernv Hari Bathini
2019-09-11 14:50 ` [PATCH v6 15/36] powerpc/fadump: improve fadump_reserve_mem() Hari Bathini
2019-09-11 14:50 ` [PATCH v6 16/36] powernv/fadump: register kernel metadata address with opal Hari Bathini
2019-09-11 14:51 ` [PATCH v6 17/36] powernv/fadump: reset metadata address during clean up Hari Bathini
2019-09-11 14:51 ` [PATCH v6 18/36] powernv/fadump: define OPAL register/un-register callback functions Hari Bathini
2019-09-11 14:51 ` [PATCH v6 19/36] powernv/fadump: support copying multiple kernel boot memory regions Hari Bathini
2019-09-11 14:51 ` [PATCH v6 20/36] powernv/fadump: process the crashdump by exporting it as /proc/vmcore Hari Bathini
2019-09-11 14:52 ` [PATCH v6 21/36] powernv/fadump: Warn before processing partial crashdump Hari Bathini
2019-09-11 14:53 ` [PATCH v6 22/36] powernv/fadump: handle invalidation of crashdump and re-registraion Hari Bathini
2019-09-11 14:53 ` Hari Bathini [this message]
2019-09-11 14:54 ` [PATCH v6 24/36] powerpc/fadump: make use of memblock's bottom up allocation mode Hari Bathini
2019-09-11 14:54 ` [PATCH v6 25/36] powernv/fadump: process architected register state data provided by firmware Hari Bathini
2019-09-11 14:55 ` [PATCH v6 26/36] powerpc/fadump: make crash memory ranges array allocation generic Hari Bathini
2019-09-11 14:55 ` [PATCH v6 27/36] powerpc/fadump: consider reserved ranges while releasing memory Hari Bathini
2019-09-11 14:55 ` [PATCH v6 28/36] powerpc/fadump: improve how crashed kernel's memory is reserved Hari Bathini
2019-09-11 14:56 ` [PATCH v6 29/36] powernv/fadump: add support to preserve crash data on FADUMP disabled kernel Hari Bathini
2019-09-11 14:56 ` [PATCH v6 30/36] powerpc/fadump: update documentation about CONFIG_PRESERVE_FA_DUMP Hari Bathini
2019-09-11 14:56 ` [PATCH v6 31/36] powernv/opalcore: export /sys/firmware/opal/core for analysing opal crashes Hari Bathini
2019-09-11 14:56 ` [PATCH v6 32/36] powernv/opalcore: provide an option to invalidate /sys/firmware/opal/core file Hari Bathini
2019-09-11 14:56 ` [PATCH v6 33/36] powerpc/fadump: consider f/w load area Hari Bathini
2019-09-11 14:57 ` [PATCH v6 34/36] powernv/fadump: update documentation about option to release opalcore Hari Bathini
2019-09-11 14:57 ` [PATCH v6 35/36] powerpc/fadump: remove RMA_START and RMA_END macros Hari Bathini
2019-09-11 14:57 ` [PATCH v6 36/36] powernv/fadump: support holes in kernel boot memory area Hari Bathini

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