redonkable
/
alistair23-linux
1
0
Fork 0
Code Releases Activity

powerpc/fadump: Improve fadump documentation 

The figures depicting FADump's (Firmware-Assisted Dump) memory layout
are missing some finer details like different memory regions and what
they represent. Improve the documentation by updating those details.

Signed-off-by: Hari Bathini <hbathini@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/156821322070.5656.8194734198500730487.stgit@hbathini.in.ibm.com
alistair/sunxi64-5.4-dsi
Hari Bathini 2019-09-11 20:17:07 +05:30 committed by Michael Ellerman
parent 7f0ad11d3f
commit 8468d15545
1 changed files with 33 additions and 28 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

61
Documentation/powerpc/firmware-assisted-dump.rst
View File

@ -76,8 +76,9 @@ as follows:
there is crash data available from a previous boot. During there is crash data available from a previous boot. During
the early boot OS will reserve rest of the memory above the early boot OS will reserve rest of the memory above
boot memory size effectively booting with restricted memory boot memory size effectively booting with restricted memory
size. This will make sure that the second kernel will not size. This will make sure that this kernel (also, referred
touch any of the dump memory area. to as second kernel or capture kernel) will not touch any
of the dump memory area.
- User-space tools will read /proc/vmcore to obtain the contents - User-space tools will read /proc/vmcore to obtain the contents
of memory, which holds the previous crashed kernel dump in ELF of memory, which holds the previous crashed kernel dump in ELF
@ -128,42 +129,46 @@ space memory except the user pages that were present in CMA region::
o Memory Reservation during first kernel o Memory Reservation during first kernel
Low memory Top of memory Low memory Top of memory
0 boot memory size | 0 boot memory size |<--Reserved dump area --->| |
| | |<--Reserved dump area -->| | | | | (Permanent Reservation) | |
V V | Permanent Reservation | V V V | | V
+-----------+----------/ /---+---+----+-----------+----+------+ +-----------+----------/ /---+---+----+--------+---+----+------+
| | |CPU|HPTE| DUMP |ELF | | | | |CPU|HPTE| DUMP |HDR|ELF | |
+-----------+----------/ /---+---+----+-----------+----+------+ +-----------+----------/ /---+---+----+--------+---+----+------+
| ^ | ^ ^
| | | | |
\ / \ / |
------------------------------------------- ----------------------------------- FADump Header
Boot memory content gets transferred to Boot memory content gets transferred (meta area)
reserved area by firmware at the time of to reserved area by firmware at the
crash time of crash
Fig. 1 Fig. 1
o Memory Reservation during second kernel after crash o Memory Reservation during second kernel after crash
Low memory Top of memory Low memory Top of memory
0 boot memory size | 0 boot memory size |
| |<------------- Reserved dump area ----------- -->| | |<----------- Crash preserved area --------------->|
V V V V V |<-- Reserved dump area -->| V
+-----------+----------/ /---+---+----+-----------+----+------+ +-----------+----------/ /---+---+----+--------+---+----+------+
| | |CPU|HPTE| DUMP |ELF | | | | |CPU|HPTE| DUMP |HDR|ELF | |
+-----------+----------/ /---+---+----+-----------+----+------+ +-----------+----------/ /---+---+----+--------+---+----+------+
| | | |
V V V V
Used by second /proc/vmcore Used by second /proc/vmcore
kernel to boot kernel to boot
Fig. 2 Fig. 2
Currently the dump will be copied from /proc/vmcore to a Currently the dump will be copied from /proc/vmcore to a new file upon
a new file upon user intervention. The dump data available through user intervention. The dump data available through /proc/vmcore will be
/proc/vmcore will be in ELF format. Hence the existing kdump in ELF format. Hence the existing kdump infrastructure (kdump scripts)
infrastructure (kdump scripts) to save the dump works fine with to save the dump works fine with minor modifications. KDump scripts on
minor modifications. major Distro releases have already been modified to work seemlessly (no
user intervention in saving the dump) when FADump is used, instead of
KDump, as dump mechanism.
The tools to examine the dump will be same as the ones The tools to examine the dump will be same as the ones
used for kdump. used for kdump.