Re: [PATCH v5 6/8] hw/ppc: Enable fadump for PSeries

[Sourabh Jain <sourabhjain@linux.ibm.com>]

On 21/10/25 19:18, Aditya Gupta wrote:
> With all support in place for preserving memory regions, enable fadump by
> exporting the "ibm,kernel-dump" property in the device tree, representing
> the fadump dump information, in case of a crash.
>
> Currently "ibm,configure-kernel-dump" RTAS call is already registered,
> which tells the kernel that the platform (QEMU) supports fadump.
>
> Now, in case of a crash, if fadump was registered, we also pass
> "ibm,kernel-dump" in device tree, which tells the kernel that the fadump
> dump is active.
>
> Pass "fadump=on" to enable Linux to use firmware assisted dump.
>
> Logs of a linux boot with firmware assisted dump:
>
>      $ ./build/qemu-system-ppc64 -M pseries,x-vof=on --cpu power10 --smp 4 -m 4G -kernel some-vmlinux -initrd some-initrd -append "debug fadump=on crashkernel=1G" -nographic
>
>      [    0.000000] fadump: Reserved 1024MB of memory at 0x00000040000000 (System RAM: 4096MB)
>      [    0.000000] fadump: Initialized 0x40000000 bytes cma area at 1024MB from 0x400102a8 bytes of memory reserved for firmware-assisted dump
>      ...
>      [    1.084686] rtas fadump: Registration is successful!
>      ...
>      # cat /sys/kernel/debug/powerpc/fadump_region
>      CPU :[0x00000040000000-0x000000400013df] 0x13e0 bytes, Dumped: 0x0
>      HPTE:[0x000000400013e0-0x000000400013df] 0x0 bytes, Dumped: 0x0
>      DUMP: Src: 0x00000000000000, Dest: 0x00000040010000, Size: 0x40000000, Dumped: 0x0 bytes
>
>      [0x0000000921a000-0x0000000921a7ff]: cmdline append: ''
>      # echo c > /proc/sysrq-trigger
>
> The fadump boot after crash:
>
>      [    0.000000] rtas fadump: Firmware-assisted dump is active.
>      [    0.000000] fadump: Updated cmdline: debug fadump=on crashkernel=1G
>      [    0.000000] fadump: Firmware-assisted dump is active.
>      [    0.000000] fadump: Reserving 3072MB of memory at 0x00000040000000 for preserving crash data
>      ....
>      # file /proc/vmcore
>      /proc/vmcore: ELF 64-bit LSB core file, 64-bit PowerPC or cisco 7500, OpenPOWER ELF V2 ABI, version 1 (SYSV), SVR4-style
>
> Analysing the vmcore with crash-utility:
>
>            KERNEL: vmlinux-6.14-rc2
>          DUMPFILE: vmcore-fc92fb373aa0
>              CPUS: 4
>              DATE: Wed Mar 12 23:39:23 CDT 2025
>            UPTIME: 00:00:22
>      LOAD AVERAGE: 0.13, 0.03, 0.01
>             TASKS: 95
>          NODENAME: buildroot
>           RELEASE: 6.12.0-rc4+
>           VERSION: #1 SMP Fri Jan  3 00:15:17 IST 2025
>           MACHINE: ppc64le  (1000 Mhz)
>            MEMORY: 4 GB
>             PANIC: "Kernel panic - not syncing: sysrq triggered crash"
>               PID: 269
>           COMMAND: "sh"
>              TASK: c00000000a050b00  [THREAD_INFO: c00000000a050b00]
>               CPU: 0
>             STATE: TASK_RUNNING (PANIC)
>
> Signed-off-by: Aditya Gupta <adityag@linux.ibm.com>
> ---
>   hw/ppc/spapr.c | 12 ++++++++++++
>   1 file changed, 12 insertions(+)
>
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index d40d5a9dcde5..77da8c1b02f5 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -904,6 +904,8 @@ static void spapr_dt_rtas_fadump(SpaprMachineState *spapr, void *fdt, int rtas)
>   {
>       MachineState *ms = MACHINE(spapr);
>       MachineClass *mc = MACHINE_GET_CLASS(ms);
> +    FadumpMemStruct *fdm = &spapr->registered_fdm;
> +    uint16_t dump_status_flag;
>   
>       uint32_t max_possible_cpus = mc->possible_cpu_arch_ids(ms)->len;
>       uint64_t fadump_cpu_state_size = 0;
> @@ -953,6 +955,16 @@ static void spapr_dt_rtas_fadump(SpaprMachineState *spapr, void *fdt, int rtas)
>                       fadump_versions, sizeof(fadump_versions))));
>       _FDT((fdt_setprop(fdt, rtas, "ibm,configure-kernel-dump-sizes",
>                       fadump_rgn_sizes, sizeof(fadump_rgn_sizes))));
> +
> +    dump_status_flag = be16_to_cpu(fdm->header.dump_status_flag);
> +    if (dump_status_flag & FADUMP_STATUS_DUMP_TRIGGERED) {
> +        uint64_t fdm_size =
> +            sizeof(struct FadumpSectionHeader) +
> +            (be16_to_cpu(fdm->header.dump_num_sections) *
> +            sizeof(struct FadumpSection));
> +
> +        _FDT((fdt_setprop(fdt, rtas, "ibm,kernel-dump", fdm, fdm_size)));
> +    }
>   }
>   
>   static void spapr_dt_rtas(SpaprMachineState *spapr, void *fdt)

LGTM
Reviewed-by: Sourabh Jain <sourabhjain@linux.ibm.com>