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authorHari Bathini <hbathini@linux.ibm.com>2019-09-11 17:47:07 +0300
committerMichael Ellerman <mpe@ellerman.id.au>2019-09-13 17:04:41 +0300
commit8468d155450c89adbb400cdae42bd4095f3045a9 (patch)
tree3ef6c934629d125c019968e2d0c3bd17f74edfce /Documentation/powerpc
parent7f0ad11d3fb948a0d7770bd38ae17a51413c3dac (diff)
downloadlinux-8468d155450c89adbb400cdae42bd4095f3045a9.tar.xz
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
Diffstat (limited to 'Documentation/powerpc')
-rw-r--r--Documentation/powerpc/firmware-assisted-dump.rst61
1 files changed, 33 insertions, 28 deletions
diff --git a/Documentation/powerpc/firmware-assisted-dump.rst b/Documentation/powerpc/firmware-assisted-dump.rst
index 9ca12830a48e..563c021df539 100644
--- a/Documentation/powerpc/firmware-assisted-dump.rst
+++ b/Documentation/powerpc/firmware-assisted-dump.rst
@@ -76,8 +76,9 @@ as follows:
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
- size. This will make sure that the second kernel will not
- touch any of the dump memory area.
+ size. This will make sure that this kernel (also, referred
+ 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
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
- Low memory Top of memory
- 0 boot memory size |
- | | |<--Reserved dump area -->| |
- V V | Permanent Reservation | V
- +-----------+----------/ /---+---+----+-----------+----+------+
- | | |CPU|HPTE| DUMP |ELF | |
- +-----------+----------/ /---+---+----+-----------+----+------+
- | ^
- | |
- \ /
- -------------------------------------------
- Boot memory content gets transferred 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
+ +-----------+----------/ /---+---+----+--------+---+----+------+
+ | | |CPU|HPTE| DUMP |HDR|ELF | |
+ +-----------+----------/ /---+---+----+--------+---+----+------+
+ | ^ ^
+ | | |
+ \ / |
+ ----------------------------------- FADump Header
+ Boot memory content gets transferred (meta area)
+ to reserved area by firmware at the
+ time of crash
+
Fig. 1
+
o Memory Reservation during second kernel after crash
- Low memory Top of memory
- 0 boot memory size |
- | |<------------- Reserved dump area ----------- -->|
- V V V
- +-----------+----------/ /---+---+----+-----------+----+------+
- | | |CPU|HPTE| DUMP |ELF | |
- +-----------+----------/ /---+---+----+-----------+----+------+
+ 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
kernel to boot
Fig. 2
-Currently the dump will be copied from /proc/vmcore to a
-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) to save the dump works fine with
-minor modifications.
+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)
+to save the dump works fine with minor modifications. KDump scripts on
+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
used for kdump.