@@ -117,6 +117,17 @@ to ensure that crash data is preserved to process later.
e.g.
# echo 1 > /sys/kernel/fadump_release_opalcore
+To process dump on OPAL platform, additional meta data (PIR to
+Logical CPU map) from the crashing kernel is required. This info
+has to be backed up by the crashing kernel for capture kernel to
+use it in making sense of the register state data provided by the
+F/W. The start address of the area where this info is backed up
+is stored at the tail end of FADump crash info header. To indicate
+the presence of this additional meta data (backup info), the magic
+number field in FADump crash info header is overloaded as version
+identifier.
+
+
Implementation details:
----------------------
@@ -131,12 +142,12 @@ that are run. If there is dump data, then the
memory is held.
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
+hold CPU state, HPTE region, boot memory dump, FADump header, elfcore
+header and backup area, 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.
+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
@@ -150,19 +161,19 @@ 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 Reservatio | |
- V V | (Preserve area) | V
- +-----------+--------/ /---+---+----+-------+-----+-----+-------+
- | | |///|////| DUMP | HDR | ELF | |
- +-----------+--------/ /---+---+----+-------+-----+-----+-------+
- | ^ ^ ^ ^
- | | | | |
- \ CPU HPTE / |
- --------------------------------- |
- Boot memory content gets transferred |
- to reserved area by firmware at the |
+ Low memory Top of memory
+ 0 boot memory size |<---- Reserved dump area ---->| |
+ | | | Permanent Reservation | |
+ V V | (Preserve area) | V
+ +-----------+--------/ /---+---+----+-------+-----+----+--+-------+
+ | | |///|////| DUMP |HDR|/|ELF |//| |
+ +-----------+--------/ /---+---+----+-------+-----+----+--+-------+
+ | ^ ^ ^ ^ | ^^
+ | | | | | | ||
+ \ CPU HPTE / | \ / Backup Info
+ --------------------------------- | ----
+ Boot memory content gets transferred | Start address of
+ to reserved area by firmware at the | Backup Info.
time of crash. |
FADump Header
(meta area)
@@ -171,13 +182,13 @@ that were present in CMA region.
o Memory Reservation during second kernel after crash
- Low memory Top of memory
- 0 boot memory size |
- | |<--------------- Reserved dump area -------------->|
- V V |<---- Preserve area ------->| |
- +-----------+--------/ /---+---+----+-------+-----+-----+-------+
- | | |///|////| DUMP | HDR | ELF | |
- +-----------+--------/ /---+---+----+-------+-----+-----+-------+
+ Low memory Top of memory
+ 0 boot memory size |
+ | |<--------------- Reserved dump area ---------------->|
+ V V |<----- Preserve area -------->| |
+ +-----------+--------/ /---+---+----+-------+-----+----+--+-------+
+ | | |///|////| DUMP |HDR|/|ELF |//| |
+ +-----------+--------/ /---+---+----+-------+-----+----+--+-------+
| |
V V
Used by second /proc/vmcore
@@ -185,9 +196,10 @@ that were present in CMA region.
Fig. 2
+---+
- |///| -> Regions (CPU & HPTE) marked like this in the above figures
- +---+ are not always present. For example, OPAL platform does not
- have CPU & HPTE regions.
+ |///| -> Regions (CPU, HPTE, HDR extension & Backup area) marked
+ +---+ like this in the above figures are not always present.
+ For example, OPAL platform does not have CPU & HPTE regions
+ while PSeries platform doesn't use Backup area currently.
Currently the dump will be copied from /proc/vmcore to a new file upon
@@ -330,7 +342,10 @@ TODO:
2. Reserve the area of predefined size (say PAGE_SIZE) for this
structure and have unused area as reserved (initialized to zero)
for future field additions.
+
The advantage of approach 1 over 2 is we don't need to reserve extra space.
+ Using approach 1 to provide additional meta data on OPAL platform while
+ overloading magic number field as version identifier for version tracking.
---
Author: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
This document is based on the original documentation written for phyp
With backup area support available for FADump on PowerNV platform, update FADump documentation with these details. Signed-off-by: Hari Bathini <hbathini@linux.ibm.com> --- Documentation/powerpc/firmware-assisted-dump.txt | 71 +++++++++++++--------- 1 file changed, 43 insertions(+), 28 deletions(-)