On 28/07/20 8:02 am, piliu wrote:
On 07/27/2020 03:36 AM, Hari Bathini wrote:
Sorry! There was a gateway issue on my system while posting v5, due to
which some patches did not make it through. Resending...
This patch series enables kdump support for kexec_file_load system
call (kexec -s -p) on PPC64. The changes are inspired from kexec-tools
code but heavily modified for kernel consumption.
The first patch adds a weak arch_kexec_locate_mem_hole() function to
override locate memory hole logic suiting arch needs. There are some
special regions in ppc64 which should be avoided while loading buffer
& there are multiple callers to kexec_add_buffer making it complicated
to maintain range sanity and using generic lookup at the same time.
The second patch marks ppc64 specific code within arch/powerpc/kexec
and arch/powerpc/purgatory to make the subsequent code changes easy
to understand.
The next patch adds helper function to setup different memory ranges
needed for loading kdump kernel, booting into it and exporting the
crashing kernel's elfcore.
The fourth patch overrides arch_kexec_locate_mem_hole() function to
locate memory hole for kdump segments by accounting for the special
memory regions, referred to as excluded memory ranges, and sets
kbuf->mem when a suitable memory region is found.
The fifth patch moves walk_drmem_lmbs() out of .init section with
a few changes to reuse it for setting up kdump kernel's usable memory
ranges. The next patch uses walk_drmem_lmbs() to look up the LMBs
and set linux,drconf-usable-memory & linux,usable-memory properties
in order to restrict kdump kernel's memory usage.
The seventh patch updates purgatory to setup r8 & r9 with opal base
and opal entry addresses respectively to aid kernels built with
CONFIG_PPC_EARLY_DEBUG_OPAL enabled. The next patch setups up backup
region as a kexec segment while loading kdump kernel and teaches
purgatory to copy data from source to destination.
Patch 09 builds the elfcore header for the running kernel & passes
the info to kdump kernel via "elfcorehdr=" parameter to export as
/proc/vmcore file. The next patch sets up the memory reserve map
for the kexec kernel and also claims kdump support for kdump as
all the necessary changes are added.
The last patch fixes a lookup issue for `kexec -l -s` case when
memory is reserved for crashkernel.
Tested the changes successfully on P8, P9 lpars, couple of OpenPOWER
boxes, one with secureboot enabled, KVM guest and a simulator.
v4 -> v5:
* Dropped patches 07/12 & 08/12 and updated purgatory to do everything
in assembly.
Hello Pingfan,
Sorry, I missed out on responding to this.
I guess you achieve this by carefully selecting instruction to avoid
relocation issue, right?
Yes. No far branching or reference to data from elsewhere.
Thanks
Hari
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