Re: [PATCH v4 0/8] Implement Firmware Assisted Dump for PSeries

[Harsh Prateek Bora <harshpb@linux.ibm.com>]

+ Shivang - FYI

Hi Aditya,
Could you please keep Shivang in Cc when you post v5 ? TIA.

regards,
Harsh

On 3/23/25 23:09, Aditya Gupta wrote:
> 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
>