Re: [PATCH 6/6] hw/ppc: Enable Fadump for PSeries

["Nicholas Piggin" <npiggin@gmail.com>]

On Mon Feb 17, 2025 at 5:17 PM AEST, Aditya Gupta wrote:
> With all support in place, enable fadump by exporting the
> "ibm,configure-kernel-dump" RTAS call in the device tree.
>
> Presence of "ibm,configure-kernel-dump" tells the kernel that the
> platform (QEMU) supports fadump.
>
> 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] random: crng init done
>     [    0.000000] fadump: Reserved 1024MB of memory at 0x00000040000000 (System RAM: 4096MB)
>     ...
>     [    1.084686] rtas fadump: Registration is successful!
>     ...
>     # cat /sys/kernel/debug/powerpc/fadump_region
>     CPU :[0x00000040000000-0x000000400013d3] 0x13d4 bytes, Dumped: 0x0
>     HPTE:[0x000000400013d4-0x000000400013d3] 0x0 bytes, Dumped: 0x0
>     DUMP: Src: 0x00000000000000, Dest: 0x00000040010000, Size: 0x40000000, Dumped: 0x0 bytes
>
>     [0x000000fffff800-0x000000ffffffff]: 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-a64dcfb451e2-nocma
>             CPUS: 4
>             DATE: Thu Jan  1 05:30:00 IST 1970
>           UPTIME: 00:00:30
>     LOAD AVERAGE: 0.74, 0.21, 0.07
>            TASKS: 94
>         NODENAME: buildroot
>          RELEASE: 6.14.0-rc2+
>          VERSION: #1 SMP Wed Feb 12 06:49:59 CST 2025
>          MACHINE: ppc64le  (1000 Mhz)
>           MEMORY: 4 GB
>            PANIC: "Kernel panic - not syncing: sysrq triggered crash"
>              PID: 270
>          COMMAND: "sh"
>             TASK: c000000009e7cc00  [THREAD_INFO: c000000009e7cc00]
>              CPU: 3
>            STATE: TASK_RUNNING (PANIC)
>
> Signed-off-by: Aditya Gupta <adityag@linux.ibm.com>

This is very cool, nice work. Does it work with KVM? I think... probably
it could?

Are you able to add a functional test case for it? This is something
that people (including me) will forget to test...

Thanks,
Nick

> ---
>  hw/ppc/spapr_rtas.c    | 6 +++++-
>  include/hw/ppc/spapr.h | 3 ++-
>  2 files changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/hw/ppc/spapr_rtas.c b/hw/ppc/spapr_rtas.c
> index 0aca4270aee8..bd2ed16a46e3 100644
> --- a/hw/ppc/spapr_rtas.c
> +++ b/hw/ppc/spapr_rtas.c
> @@ -692,7 +692,7 @@ static void trigger_fadump_boot(target_ulong spapr_retcode)
>  }
>  
>  /* Papr Section 7.4.9 ibm,configure-kernel-dump RTAS call */
> -static __attribute((unused)) void rtas_configure_kernel_dump(PowerPCCPU *cpu,
> +static void rtas_configure_kernel_dump(PowerPCCPU *cpu,
>                                     SpaprMachineState *spapr,
>                                     uint32_t token, uint32_t nargs,
>                                     target_ulong args,
> @@ -1109,6 +1109,10 @@ static void core_rtas_register_types(void)
>      spapr_rtas_register(RTAS_IBM_NMI_INTERLOCK, "ibm,nmi-interlock",
>                          rtas_ibm_nmi_interlock);
>  
> +    /* Register Fadump rtas call */
> +    spapr_rtas_register(RTAS_CONFIGURE_KERNEL_DUMP, "ibm,configure-kernel-dump",
> +                        rtas_configure_kernel_dump);
> +
>      qtest_set_command_cb(spapr_qtest_callback);
>  }
>  
> diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
> index fa63008e57ec..bde3bdc4b80c 100644
> --- a/include/hw/ppc/spapr.h
> +++ b/include/hw/ppc/spapr.h
> @@ -768,8 +768,9 @@ void push_sregs_to_kvm_pr(SpaprMachineState *spapr);
>  #define RTAS_IBM_SUSPEND_ME                     (RTAS_TOKEN_BASE + 0x2A)
>  #define RTAS_IBM_NMI_REGISTER                   (RTAS_TOKEN_BASE + 0x2B)
>  #define RTAS_IBM_NMI_INTERLOCK                  (RTAS_TOKEN_BASE + 0x2C)
> +#define RTAS_CONFIGURE_KERNEL_DUMP              (RTAS_TOKEN_BASE + 0x2D)
>  
> -#define RTAS_TOKEN_MAX                          (RTAS_TOKEN_BASE + 0x2D)
> +#define RTAS_TOKEN_MAX                          (RTAS_TOKEN_BASE + 0x2E)
>  
>  /* Fadump commands */
>  #define FADUMP_CMD_REGISTER            1