Re: [PATCH 5/6] hw/ppc: Pass device tree properties for Fadump

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

On 2/27/25 08:58, Nicholas Piggin wrote:
> On Mon Feb 17, 2025 at 5:17 PM AEST, Aditya Gupta wrote:
>> Platform (ie. QEMU) is expected to pass few device tree properties for
>> details for fadump:
>>
>>    * "ibm,configure-kernel-dump": RTAS call for fadump
>>    * "ibm,configure-kernel-dump-sizes": Space required to store dump data
>>      for firmware provided dump sections (ie. CPU & HPTE regions)
>>    * "ibm,configure-kernel-dump-version": Versions of fadump supported
>>    * "ibm,kernel-dump": Contains the Fadump Memory Structure on a fadump
>>      boot
>>
>> Implement passing configure-kernel-dump-sizes, and
>> configure-kernel-dump-version device tree properties, irrespective of
>> whether it's a fadump boot or not, so that kernel can reserve memory to
>> store the firmware provided dump sections in case of a crash
>>
>> Also, in case of a fadump boot, pass the fadump memory structure to the
>> kernel in "ibm,kernel-dump" device tree property.
>>
>> Signed-off-by: Aditya Gupta <adityag@linux.ibm.com>
>> ---
>>   hw/ppc/spapr.c         | 62 ++++++++++++++++++++++++++++++++++++++++++
>>   include/hw/ppc/spapr.h |  2 ++
>>   2 files changed, 64 insertions(+)
>>
>> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
>> index f3a4b4235d43..3602e5b5d18d 100644
>> --- a/hw/ppc/spapr.c
>> +++ b/hw/ppc/spapr.c
>> @@ -897,9 +897,27 @@ static int spapr_dt_rng(void *fdt)
>>   static void spapr_dt_rtas(SpaprMachineState *spapr, void *fdt)
>>   {
> 
> You might be able to add a spapr_dt_rtas_fadump() function
> and do it there to help keep functions small?

Ditto. Would look nicer coming from spapr_fadump.[ch] as suggested by 
Nick earlier.

Thanks
Harsh
> 
> Thanks,
> Nick
> 
>>       MachineState *ms = MACHINE(spapr);
>> +    MachineClass *mc = MACHINE_GET_CLASS(ms);
>>       int rtas;
>>       GString *hypertas = g_string_sized_new(256);
>>       GString *qemu_hypertas = g_string_sized_new(256);
>> +    uint32_t max_possible_cpus = mc->possible_cpu_arch_ids(ms)->len;
>> +    uint64_t fadump_cpu_state_size = 0;
>> +    uint16_t fadump_versions[2] = {
>> +        FADUMP_VERSION /* min supported version */,
>> +        FADUMP_VERSION /* max supported version */
>> +    };
>> +    uint32_t fadump_rgn_sizes[2][3] = {
>> +        {
>> +            cpu_to_be32(FADUMP_CPU_STATE_DATA),
>> +            0, 0 /* Calculated later */
>> +        },
>> +        {
>> +            cpu_to_be32(FADUMP_HPTE_REGION),
>> +            0, 0 /* HPTE region not implemented */
>> +        }
>> +    };
>> +
>>       uint32_t lrdr_capacity[] = {
>>           0,
>>           0,
>> @@ -1006,6 +1024,50 @@ static void spapr_dt_rtas(SpaprMachineState *spapr, void *fdt)
>>       _FDT(fdt_setprop(fdt, rtas, "ibm,lrdr-capacity",
>>                        lrdr_capacity, sizeof(lrdr_capacity)));
>>   
>> +    /*
>> +     * CPU State Data contains multiple fields such as header, num_cpus and
>> +     * register entries
>> +     *
>> +     * Calculate the maximum CPU State Data size, according to maximum
>> +     * possible CPUs the QEMU VM can have
>> +     */
>> +    /* Reg save header */
>> +    fadump_cpu_state_size += sizeof(struct rtas_fadump_reg_save_area_header);
>> +
>> +    /* Num_cpus */
>> +    fadump_cpu_state_size += sizeof(__be32);
>> +
>> +    /* Register Entries */
>> +    fadump_cpu_state_size += max_possible_cpus   *
>> +                             FADUMP_NUM_PER_CPU_REGS *
>> +                             sizeof(struct rtas_fadump_reg_entry);
>> +
>> +    /* Set maximum size for CPU state data region */
>> +    assert(fadump_rgn_sizes[0][0] == cpu_to_be32(FADUMP_CPU_STATE_DATA));
>> +
>> +    /* Upper 32 bits of size, usually 0 */
>> +    fadump_rgn_sizes[0][1] = cpu_to_be32(fadump_cpu_state_size >> 32);
>> +
>> +    /* Lower 32 bits of size */
>> +    fadump_rgn_sizes[0][2] = cpu_to_be32(fadump_cpu_state_size & 0xffffffff);
>> +
>> +    /* Add device tree properties required from platform for fadump */
>> +    _FDT((fdt_setprop(fdt, rtas, "ibm,configure-kernel-dump-version",
>> +                    fadump_versions, sizeof(fadump_versions))));
>> +    _FDT((fdt_setprop(fdt, rtas, "ibm,configure-kernel-dump-sizes",
>> +                    fadump_rgn_sizes, sizeof(fadump_rgn_sizes))));
>> +
>> +    if (is_next_boot_fadump) {
>> +        struct rtas_fadump_mem_struct *fdm =
>> +            &fadump_metadata.registered_fdm;
>> +
>> +        uint64_t fdm_size =
>> +            sizeof(struct rtas_fadump_section_header) +
>> +            (be16_to_cpu(fdm->header.dump_num_sections) *
>> +            sizeof(struct rtas_fadump_section));
>> +
>> +        _FDT((fdt_setprop(fdt, rtas, "ibm,kernel-dump", fdm, fdm_size)));
>> +    }
>>       spapr_dt_rtas_tokens(fdt, rtas);
>>   }
>>   
>> diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
>> index 0e8002bad9e0..fa63008e57ec 100644
>> --- a/include/hw/ppc/spapr.h
>> +++ b/include/hw/ppc/spapr.h
>> @@ -928,6 +928,8 @@ static inline uint64_t fadump_gpr_id_to_u64(uint32_t gpr_id)
>>       return val;
>>   }
>>   
>> +extern bool is_next_boot_fadump;
>> +
>>   struct fadump_metadata {
>>       bool fadump_registered;
>>       bool fadump_dump_active;
>