diff options
Diffstat (limited to 'Documentation/powerpc/firmware-assisted-dump.txt')
| -rw-r--r-- | Documentation/powerpc/firmware-assisted-dump.txt | 57 |
1 files changed, 32 insertions, 25 deletions
diff --git a/Documentation/powerpc/firmware-assisted-dump.txt b/Documentation/powerpc/firmware-assisted-dump.txt index 3007bc98af28..9cabaf8a207e 100644 --- a/Documentation/powerpc/firmware-assisted-dump.txt +++ b/Documentation/powerpc/firmware-assisted-dump.txt @@ -55,10 +55,14 @@ as follows: booted with restricted memory. By default, the boot memory size will be the larger of 5% of system RAM or 256MB. Alternatively, user can also specify boot memory size - through boot parameter 'fadump_reserve_mem=' which will - override the default calculated size. Use this option - if default boot memory size is not sufficient for second - kernel to boot successfully. + through boot parameter 'crashkernel=' which will override + 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/kdump/kdump.txt. If any offset is + provided in crashkernel= parameter, it will be ignored + as fadump reserves memory at end of RAM for boot memory + dump preservation in case of a crash. -- After the low memory (boot memory) area has been saved, the firmware will reset PCI and other hardware state. It will @@ -105,21 +109,21 @@ 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 reserved at the top of memory (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. +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. o Memory Reservation during first kernel - Low memory Top of memory + Low memory Top of memory 0 boot memory size | - | | |<--Reserved dump area -->| - V V | Permanent Reservation V - +-----------+----------/ /----------+---+----+-----------+----+ - | | |CPU|HPTE| DUMP |ELF | - +-----------+----------/ /----------+---+----+-----------+----+ + | | |<--Reserved dump area -->| | + V V | Permanent Reservation | V + +-----------+----------/ /---+---+----+-----------+----+------+ + | | |CPU|HPTE| DUMP |ELF | | + +-----------+----------/ /---+---+----+-----------+----+------+ | ^ | | \ / @@ -135,12 +139,12 @@ crash does occur. 0 boot memory size | | |<------------- Reserved dump area ----------- -->| V V V - +-----------+----------/ /----------+---+----+-----------+----+ - | | |CPU|HPTE| DUMP |ELF | - +-----------+----------/ /----------+---+----+-----------+----+ - | | - V V - Used by second /proc/vmcore + +-----------+----------/ /---+---+----+-----------+----+------+ + | | |CPU|HPTE| DUMP |ELF | | + +-----------+----------/ /---+---+----+-----------+----+------+ + | | + V V + Used by second /proc/vmcore kernel to boot Fig. 2 @@ -158,13 +162,16 @@ How to enable firmware-assisted dump (fadump): 1. Set config option CONFIG_FA_DUMP=y and build kernel. 2. Boot into linux kernel with 'fadump=on' kernel cmdline option. -3. Optionally, user can also set 'fadump_reserve_mem=' kernel cmdline +3. Optionally, user can also set 'crashkernel=' kernel cmdline to specify size of the memory to reserve for boot memory dump preservation. -NOTE: If firmware-assisted dump fails to reserve memory then it will - fallback to existing kdump mechanism if 'crashkernel=' option - is set at kernel cmdline. +NOTE: 1. 'fadump_reserve_mem=' parameter has been deprecated. Instead + use 'crashkernel=' to specify size of the memory to reserve + for boot memory dump preservation. + 2. If firmware-assisted dump fails to reserve memory then it + will fallback to existing kdump mechanism if 'crashkernel=' + option is set at kernel cmdline. Sysfs/debugfs files: ------------ |