Re: [PATCH v2] ppc/pnv: generate dtb after machine initialization is complete

[Nathan Chancellor <nathan@kernel.org>]

On Fri, Mar 27, 2026 at 06:11:36PM +0530, Shivang Upadhyay wrote:
> Currently, the machine dtb is generated in pnv_init(), before all devices
> are fully initialized. This can result in an incomplete dtb for the system,
> as seen in bug [1].
> 
> Fix this by deferring dtb generation until machine initialization is complete,
> using the machine_init_done_notifier hook.
> 
> [1] https://lore.kernel.org/all/20260323231612.GA2637687@ax162/
> 
> Cc: Aditya Gupta <adityag@linux.ibm.com>
> Cc: Harsh Prateek Bora <harshpb@linux.ibm.com>
> Cc: BALATON Zoltan <balaton@eik.bme.hu>
> Cc: qemu-stable@nongnu.org
> Reported-by: Nathan Chancellor <nathan@kernel.org>
> Suggested-by: Peter Maydell <peter.maydell@linaro.org>
> Fixes: a16d4c2f162a86d ("ppc/pnv: fix dumpdtb option")
> Signed-off-by: Shivang Upadhyay <shivangu@linux.ibm.com>

This still works for me.

Tested-by: Nathan Chancellor <nathan@kernel.org>

> ---
> Changes:
> 
> v2:
> * moved pnv->bmc initialization to pnv_machine_init_done.
> 
> v1:
> * https://lore.kernel.org/all/20260324135026.247418-1-shivangu@linux.ibm.com/
> ---
>  hw/ppc/pnv.c         | 58 +++++++++++++++++++++++++-------------------
>  include/hw/ppc/pnv.h |  2 ++
>  2 files changed, 35 insertions(+), 25 deletions(-)
> 
> diff --git a/hw/ppc/pnv.c b/hw/ppc/pnv.c
> index 7e54b6bc60..524563dcfc 100644
> --- a/hw/ppc/pnv.c
> +++ b/hw/ppc/pnv.c
> @@ -748,31 +748,10 @@ static void pnv_powerdown_notify(Notifier *n, void *opaque)
>  
>  static void pnv_reset(MachineState *machine, ResetType type)
>  {
> -    PnvMachineState *pnv = PNV_MACHINE(machine);
> -    IPMIBmc *bmc;
>      void *fdt;
>  
>      qemu_devices_reset(type);
>  
> -    /*
> -     * The machine should provide by default an internal BMC simulator.
> -     * If not, try to use the BMC device that was provided on the command
> -     * line.
> -     */
> -    bmc = pnv_bmc_find(&error_fatal);
> -    if (!pnv->bmc) {
> -        if (!bmc) {
> -            if (!qtest_enabled()) {
> -                warn_report("machine has no BMC device. Use '-device "
> -                            "ipmi-bmc-sim,id=bmc0 -device isa-ipmi-bt,bmc=bmc0,irq=10' "
> -                            "to define one");
> -            }
> -        } else {
> -            pnv_bmc_set_pnor(bmc, pnv->pnor);
> -            pnv->bmc = bmc;
> -        }
> -    }
> -
>      fdt = machine->fdt;
>      cpu_physical_memory_write(PNV_FDT_ADDR, fdt, fdt_totalsize(fdt));
>  }
> @@ -984,6 +963,37 @@ static uint64_t pnv_chip_get_ram_size(PnvMachineState *pnv, int chip_id)
>      return chip_id == 0 ? 1 * GiB : QEMU_ALIGN_DOWN(ram_per_chip, 1 * MiB);
>  }
>  
> +static void pnv_machine_init_done(Notifier *notifier, void *data)
> +{
> +    PnvMachineState *pnv = container_of(notifier, PnvMachineState, machine_init_done);
> +    MachineState *machine = MACHINE(pnv);
> +    IPMIBmc *bmc;
> +
> +    /*
> +     * The machine should provide by default an internal BMC simulator.
> +     * If not, try to use the BMC device that was provided on the command
> +     * line.
> +     */
> +    bmc = pnv_bmc_find(&error_fatal);
> +    if (!pnv->bmc) {
> +        if (!bmc) {
> +            if (!qtest_enabled()) {
> +                warn_report("machine has no BMC device. Use '-device "
> +                            "ipmi-bmc-sim,id=bmc0 -device isa-ipmi-bt,bmc=bmc0,irq=10' "
> +                            "to define one");
> +            }
> +        } else {
> +            pnv_bmc_set_pnor(bmc, pnv->pnor);
> +            pnv->bmc = bmc;
> +        }
> +    }
> +
> +    if (!machine->fdt) {
> +        machine->fdt = pnv_dt_create(machine);
> +        _FDT((fdt_pack(machine->fdt)));
> +    }
> +}
> +
>  static void pnv_init(MachineState *machine)
>  {
>      const char *bios_name = machine->firmware ?: FW_FILE_NAME;
> @@ -1244,10 +1254,8 @@ static void pnv_init(MachineState *machine)
>          pmc->i2c_init(pnv);
>      }
>  
> -    if (!machine->fdt) {
> -        machine->fdt = pnv_dt_create(machine);
> -        _FDT((fdt_pack(machine->fdt)));
> -    }
> +    pnv->machine_init_done.notify = pnv_machine_init_done;
> +    qemu_add_machine_init_done_notifier(&pnv->machine_init_done);
>  }
>  
>  /*
> diff --git a/include/hw/ppc/pnv.h b/include/hw/ppc/pnv.h
> index 24f8843a40..90028f974d 100644
> --- a/include/hw/ppc/pnv.h
> +++ b/include/hw/ppc/pnv.h
> @@ -111,6 +111,8 @@ struct PnvMachineState {
>  
>      bool         big_core;
>      bool         lpar_per_core;
> +
> +    Notifier     machine_init_done;
>  };
>  
>  PnvChip *pnv_get_chip(PnvMachineState *pnv, uint32_t chip_id);
> -- 
> 2.53.0
>