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

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

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?

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;