On 7/16/19 5:02 PM, Hari Bathini wrote: > 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 <hbath...@linux.ibm.com> > --- > Documentation/powerpc/firmware-assisted-dump.txt | 65 > ++++++++++++---------- > 1 file changed, 35 insertions(+), 30 deletions(-) > > diff --git a/Documentation/powerpc/firmware-assisted-dump.txt > b/Documentation/powerpc/firmware-assisted-dump.txt > index 0c41d6d..e9b4e3c 100644 > --- a/Documentation/powerpc/firmware-assisted-dump.txt > +++ b/Documentation/powerpc/firmware-assisted-dump.txt
This will have to be rebased now on firmware-assisted-dump.rst. However Changes looks good to me. Thanks, -Mahesh. > @@ -74,8 +74,9 @@ 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 > @@ -125,48 +126,52 @@ 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 | (Preserve area) | 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 | > + | |<------------- Reserved dump area --------------->| > + V V |<---- Preserve 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. > > 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. > @@ -189,7 +194,7 @@ NOTE: 1. 'fadump_reserve_mem=' parameter has been > deprecated. Instead > old behaviour. > > Sysfs/debugfs files: > ------------- > +------------------- > > Firmware-assisted dump feature uses sysfs file system to hold > the control files and debugfs file to display memory reserved region. >