On Fri, Apr 17, 2020 at 05:01:50PM +0200, David Hildenbrand wrote: > The zcore memmap basically contains the first level of all system RAM from > /proc/iomem. We want to disable CONFIG_ARCH_KEEP_MEMBLOCK (e.g., to not > create memblocks for hotplugged/standby memory and save space), switch to > traversing system ram resources instead. During early boot, we create > resources for all early memblocks (including the crash kernel area). When > adding standby memory, we currently create both, memblocks and resources. > > Note: As we don't have memory hotplug after boot (standby memory is added > via sclp during boot), we don't have to worry about races. > > I am only able to test under KVM (where I hacked up zcore to still > create the memmap file) > > root@vm0:~# cat /proc/iomem > 00000000-2fffffff : System RAM > 10424000-10ec6fff : Kernel code > 10ec7000-1139a0e3 : Kernel data > 1177a000-11850fff : Kernel bss > 30000000-3fffffff : Crash kernel > > Result without this patch: > root@vm0:~# cat /sys/kernel/debug/zcore/memmap > 0000000000000000 0000000040000000 > > Result with this patch: > root@vm0:~# cat /sys/kernel/debug/zcore/memmap > 0000000000000000 0000000030000000 0000000030000000 0000000010000000 > > The difference is due to memblocks getting merged, resources (currently) > not. So we might have some more entries, but they describe the same > memory map. > > Cc: Heiko Carstens <heiko.carstens@xxxxxxxxxx> > Cc: Vasily Gorbik <gor@xxxxxxxxxxxxx> > Cc: Christian Borntraeger <borntraeger@xxxxxxxxxx> > Cc: Philipp Rudo <prudo@xxxxxxxxxxxxx> > Cc: Kirill Smelkov <kirr@xxxxxxxxxx> > Cc: Michael Holzheu <holzheu@xxxxxxxxxxxxxxxxxx> > Signed-off-by: David Hildenbrand <david@xxxxxxxxxx> > --- > drivers/s390/char/zcore.c | 61 ++++++++++++++++++++++++++++++--------- > 1 file changed, 48 insertions(+), 13 deletions(-) I'm having a hard time to find any code that ever made use of this file. After all this was only meant for our zfcp dumper, but as far as I can tell there was never code out there that read the memmap file. So the pragmatic approach would be to just change its contents, or a more progressive variant would be to remove the file completely. But maybe I'm entirely wrong... I'm leaving this up to Philipp and Alexander :)
