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 | 15 +++++++++++++++
1 file changed, 15 insertions(+)
diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index 3cbc6a7409b7..f6e666ad4344 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -904,6 +904,9 @@ 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;
+ bool is_next_boot_fadump;
uint32_t max_possible_cpus = mc->possible_cpu_arch_ids(ms)->len;
uint64_t fadump_cpu_state_size = 0;
@@ -953,6 +956,18 @@ 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);
+ is_next_boot_fadump =
+ (dump_status_flag & FADUMP_STATUS_DUMP_TRIGGERED) != 0;
+ if (is_next_boot_fadump) {
+ 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)
--
2.49.0
On 23/03/25 23:10, 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.
Kernel is printing twice about fadump 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 | 15 +++++++++++++++
> 1 file changed, 15 insertions(+)
>
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index 3cbc6a7409b7..f6e666ad4344 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -904,6 +904,9 @@ 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;
> + bool is_next_boot_fadump;
>
> uint32_t max_possible_cpus = mc->possible_cpu_arch_ids(ms)->len;
> uint64_t fadump_cpu_state_size = 0;
> @@ -953,6 +956,18 @@ 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);
> + is_next_boot_fadump =
Do we really need is_next_boot_fadump variable?
> + (dump_status_flag & FADUMP_STATUS_DUMP_TRIGGERED) != 0;
> + if (is_next_boot_fadump) {
> + 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)));
Is this common in QEMU to call _FDT to add prop to the FDT? Feels odd.
> + }
> }
>
> static void spapr_dt_rtas(SpaprMachineState *spapr, void *fdt)
Hello Sourabh,
On 25/10/18 05:34PM, Sourabh Jain wrote:
>
>
> > <...snip...>
> > 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.
>
> Kernel is printing twice about fadump is active. :)
Yeah i noticed, that seems to be the case atleast with 6.14
>
> > <...snip...>
> > MachineState *ms = MACHINE(spapr);
> > MachineClass *mc = MACHINE_GET_CLASS(ms);
> > + FadumpMemStruct *fdm = &spapr->registered_fdm;
> > + uint16_t dump_status_flag;
> > + bool is_next_boot_fadump;
> > uint32_t max_possible_cpus = mc->possible_cpu_arch_ids(ms)->len;
> > uint64_t fadump_cpu_state_size = 0;
> > @@ -953,6 +956,18 @@ 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);
> > + is_next_boot_fadump =
>
> Do we really need is_next_boot_fadump variable?
Agreed, not needed now, will remove it in v5.
>
> > + (dump_status_flag & FADUMP_STATUS_DUMP_TRIGGERED) != 0;
> > + if (is_next_boot_fadump) {
> > + 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)));
>
> Is this common in QEMU to call _FDT to add prop to the FDT? Feels odd.
Yes, that's just a wrapper for error checking in QEMU, used extensively
atleast in hw/ppc
Thanks for your reviews Sourabh !
- Aditya G
>
> > + }
> > }
> > static void spapr_dt_rtas(SpaprMachineState *spapr, void *fdt)
>
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