Overview
=========
Implemented Firmware Assisted Dump (fadump) on PSeries machine in QEMU.
Fadump is an alternative dump mechanism to kdump, in which we the firmware
does a memory preserving boot, and the second/crashkernel is booted fresh
like a normal system reset, instead of the crashed kernel loading the
second/crashkernel in case of kdump.
This requires implementing the "ibm,configure-kernel-dump" RTAS call in
QEMU.
While booting with fadump=on, Linux will register fadump memory regions.
Some memory regions like Real Mode Memory regions, and custom memory
regions declared by OS basically require copying the requested memory
range to a destination
While other memory regions are populated by the firmware/platform (QEMU in
this case), such as CPU State Data and HPTE.
We pass the sizes for these data segment to the kernel as it needs to know
how much memory to reserve (ibm,configure-kernel-dump-sizes).
Then after a crash, once Linux does a OS terminate call, we trigger fadump
if fadump was registered.
Implementing the fadump boot as:
* pause all vcpus (will save registers later)
* preserve memory regions specified by fadump
* do a memory preserving reboot (using GUEST_RESET as it doesn't clear
the memory)
And then we pass a metadata (firmware memory structure) as
"ibm,kernel-dump" in the device tree, containing all details of the
preserved memory regions to the kernel.
Refer the Patch #7/8: "hw/ppc: Enable fadump for PSeries" for logs of a
succesfful fadump crash
Note: HPTE region has not been implemented. It's not planned as of now.
Testing
=======
Has been tested with following QEMU options:
* firmware: x-vof and SLOF
* tcg & kvm
* l1 guest and l2 guest
* with/without smp
* cma/nocma
* default crashkernel values (can fail with big initrd) and crashkernel=1G
Git Tree for Testing
====================
https://github.com/adi-g15-ibm/qemu/tree/fadump-pseries-v4
Note: You will need a way to get the /proc/vmcore out of the VM for testing
with crash-utility
I use the following command line which sets up networking:
"-net user,hostfwd=tcp::10022-:22 -net nic"
And a rootfs with ssh support, then copy the /proc/vmcore with networking
(can do compression using gzip before ssh, but compression might take lot
of time if done inside the VM)
Test vmcore for Testing with crash-utility
==========================================
Can use vmlinux and vmcore available at
https://github.com/adi-g15-ibm/qemu/releases/tag/test-images-fadump-pseries-v2
Above vmcore was generated with upstream qemu with these fadump patches
applied, and in a KVM VM
A limitation with above vmcore is it was a single CPU VM
Changelog
=========
v4
+ [patch #8/8]: fixed kvm testcase, add license
v3:
+ [patch #3,7]: fix compile errors (#define declared in a later patch
but used in this patch, unused var)
+ [patch #4/8]: use 'g_autofree' for cpu buffer, and replace g_malloc with
g_try_malloc
+ [patch #5/8]: use 'g_new' instead of 'malloc', add null check for cpu
region
- nothing in other patches has been changed compared to v2
v2:
+ rearrange code so that no unused functions get introduced in any patch
+ add functional test for pseries as suggested by nick
+ fix multiple issues pointed by harsh and nick
+ fix bug in cpu register saving where it was being stored in
little-endian
- removed 'is_next_boot_fadump' and used fadump header's status flag to
store it
+ fixed multiple style issues (naming, unneeded diffs etc)
Aditya Gupta (8):
hw/ppc: Implement skeleton code for fadump in PSeries
hw/ppc: Implement fadump register command
hw/ppc: Trigger Fadump boot if fadump is registered
hw/ppc: Preserve memory regions registered for fadump
hw/ppc: Implement saving CPU state in Fadump
hw/ppc: Pass dump-sizes property for fadump in device tree
hw/ppc: Enable fadump for PSeries
tests/functional: Add test for fadump in PSeries
hw/ppc/meson.build | 1 +
hw/ppc/spapr.c | 72 +++
hw/ppc/spapr_fadump.c | 685 ++++++++++++++++++++++
hw/ppc/spapr_rtas.c | 71 +++
include/hw/ppc/spapr.h | 11 +-
include/hw/ppc/spapr_fadump.h | 121 ++++
tests/functional/meson.build | 2 +
tests/functional/qemu_test/linuxkernel.py | 59 ++
tests/functional/test_ppc64_fadump.py | 182 ++++++
9 files changed, 1203 insertions(+), 1 deletion(-)
create mode 100644 hw/ppc/spapr_fadump.c
create mode 100644 include/hw/ppc/spapr_fadump.h
create mode 100755 tests/functional/test_ppc64_fadump.py
--
2.49.0
