Re: [PATCH v2 3/6] hw/riscv: simplify riscv_compute_fdt_addr()

[Alistair Francis]

On Tue, Jan 17, 2023 at 3:34 AM Daniel Henrique Barboza
<dbarboza@ventanamicro.com> wrote:
>
> All callers are using attributes from the MachineState object. Use a
> pointer to it instead of passing dram_size (which is always
> machine->ram_size) and fdt (always machine->fdt).
>
> Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
> ---
>  hw/riscv/boot.c            | 6 +++---
>  hw/riscv/microchip_pfsoc.c | 4 ++--
>  hw/riscv/sifive_u.c        | 4 ++--
>  hw/riscv/spike.c           | 4 ++--
>  hw/riscv/virt.c            | 3 +--
>  include/hw/riscv/boot.h    | 2 +-
>  6 files changed, 11 insertions(+), 12 deletions(-)
>
> diff --git a/hw/riscv/boot.c b/hw/riscv/boot.c
> index b213a32157..508da3f5c7 100644
> --- a/hw/riscv/boot.c
> +++ b/hw/riscv/boot.c
> @@ -255,11 +255,11 @@ void riscv_load_initrd(MachineState *machine, uint64_t 
> kernel_entry)
>   *
>   * The FDT is fdt_packed() during the calculation.
>   */
> -uint32_t riscv_compute_fdt_addr(hwaddr dram_base, uint64_t mem_size,
> -                                void *fdt)
> +uint32_t riscv_compute_fdt_addr(MachineState *machine, hwaddr dram_base)
>  {
> +    void *fdt = machine->fdt;
>      uint64_t temp;
> -    hwaddr dram_end = dram_base + mem_size;
> +    hwaddr dram_end = dram_base + machine->ram_size;
>      int ret = fdt_pack(fdt);
>      int fdtsize;
>
> diff --git a/hw/riscv/microchip_pfsoc.c b/hw/riscv/microchip_pfsoc.c
> index dcdbc2cac3..a53e48e996 100644
> --- a/hw/riscv/microchip_pfsoc.c
> +++ b/hw/riscv/microchip_pfsoc.c
> @@ -641,8 +641,8 @@ static void 
> microchip_icicle_kit_machine_init(MachineState *machine)
>          }
>
>          /* Compute the fdt load address in dram */
> -        fdt_load_addr = 
> riscv_compute_fdt_addr(memmap[MICROCHIP_PFSOC_DRAM_LO].base,
> -                                              machine->ram_size, 
> machine->fdt);
> +        fdt_load_addr = riscv_compute_fdt_addr(machine,
> +                                               
> memmap[MICROCHIP_PFSOC_DRAM_LO].base);

I don't think this is correct here.

So, first up I understand we don't correctly handle this today, *but*
I see this change as a step in the wrong direction.

The problem here is that ram is split over two areas. So if
machine->ram_size is larger then 0x40000000 it is going to overflow
MICROCHIP_PFSOC_DRAM_LO and jump to MICROCHIP_PFSOC_DRAM_HI
(0x1000000000).

So we really want something like this

        /* Compute the fdt load address in dram */
        if (machine->ram_size > memmap[MICROCHIP_PFSOC_DRAM_LO].size) {
            fdt_load_addr = riscv_load_fdt(memmap[MICROCHIP_PFSOC_DRAM_HI].base,
                                           machine->ram_size -
memmap[MICROCHIP_PFSOC_DRAM_LO].size,
                                           machine->fdt);
        } else {
            fdt_load_addr = riscv_load_fdt(memmap[MICROCHIP_PFSOC_DRAM_LO].base,
                                           machine->ram_size,
                                           machine->fdt);
        }

to handle overflowing MICROCHIP_PFSOC_DRAM_LO. While this patch is
going in the wrong direction and making that more difficult

Alistair



>          riscv_load_fdt(fdt_load_addr, machine->fdt);
>
>          /* Load the reset vector */
> diff --git a/hw/riscv/sifive_u.c b/hw/riscv/sifive_u.c
> index 626d4dc2f3..ebfddf161d 100644
> --- a/hw/riscv/sifive_u.c
> +++ b/hw/riscv/sifive_u.c
> @@ -616,8 +616,8 @@ static void sifive_u_machine_init(MachineState *machine)
>          kernel_entry = 0;
>      }
>
> -    fdt_load_addr = riscv_compute_fdt_addr(memmap[SIFIVE_U_DEV_DRAM].base,
> -                                           machine->ram_size, machine->fdt);
> +    fdt_load_addr = riscv_compute_fdt_addr(machine,
> +                                           memmap[SIFIVE_U_DEV_DRAM].base);
>      riscv_load_fdt(fdt_load_addr, machine->fdt);
>
>      if (!riscv_is_32bit(&s->soc.u_cpus)) {
> diff --git a/hw/riscv/spike.c b/hw/riscv/spike.c
> index 88b9fdfc36..afd581436b 100644
> --- a/hw/riscv/spike.c
> +++ b/hw/riscv/spike.c
> @@ -324,8 +324,8 @@ static void spike_board_init(MachineState *machine)
>          kernel_entry = 0;
>      }
>
> -    fdt_load_addr = riscv_compute_fdt_addr(memmap[SPIKE_DRAM].base,
> -                                           machine->ram_size, machine->fdt);
> +    fdt_load_addr = riscv_compute_fdt_addr(machine,
> +                                           memmap[SPIKE_DRAM].base);
>      riscv_load_fdt(fdt_load_addr, machine->fdt);
>
>      /* load the reset vector */
> diff --git a/hw/riscv/virt.c b/hw/riscv/virt.c
> index 839dfaa125..cbba0b8930 100644
> --- a/hw/riscv/virt.c
> +++ b/hw/riscv/virt.c
> @@ -1307,8 +1307,7 @@ static void virt_machine_done(Notifier *notifier, void 
> *data)
>          start_addr = virt_memmap[VIRT_FLASH].base;
>      }
>
> -    fdt_load_addr = riscv_compute_fdt_addr(memmap[VIRT_DRAM].base,
> -                                           machine->ram_size, machine->fdt);
> +    fdt_load_addr = riscv_compute_fdt_addr(machine, memmap[VIRT_DRAM].base);
>      riscv_load_fdt(fdt_load_addr, machine->fdt);
>
>      /* load the reset vector */
> diff --git a/include/hw/riscv/boot.h b/include/hw/riscv/boot.h
> index 9aea7b9c46..f933de88fb 100644
> --- a/include/hw/riscv/boot.h
> +++ b/include/hw/riscv/boot.h
> @@ -47,7 +47,7 @@ target_ulong riscv_load_kernel(MachineState *machine,
>                                 target_ulong firmware_end_addr,
>                                 symbol_fn_t sym_cb);
>  void riscv_load_initrd(MachineState *machine, uint64_t kernel_entry);
> -uint32_t riscv_compute_fdt_addr(hwaddr dram_start, uint64_t dram_size, void 
> *fdt);
> +uint32_t riscv_compute_fdt_addr(MachineState *machine, hwaddr dram_start);
>  void riscv_load_fdt(uint32_t fdt_addr, void *fdt);
>  void riscv_setup_rom_reset_vec(MachineState *machine, RISCVHartArrayState 
> *harts,
>                                 hwaddr saddr,
> --
> 2.39.0
>
>