Re: [PATCH 1/6] hw/riscv: microchip_pfsoc: Use MachineState::ram and MachineClass::default_ram_id

[Igor Mammedov]

On Mon, 18 Oct 2021 23:38:24 +0800
Bin Meng <bmeng.cn@gmail.com> wrote:

> Using memory_region_init_ram(), which can't possibly handle vhost-user,
> and can't work as expected with '-numa node,memdev' options.
> 
> Use MachineState::ram instead of manually initializing RAM memory
> region, as well as by providing MachineClass::default_ram_id to
> opt in to memdev scheme.
> 
> Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
> ---
> 
>  hw/riscv/microchip_pfsoc.c | 9 +++------
>  1 file changed, 3 insertions(+), 6 deletions(-)
> 
> diff --git a/hw/riscv/microchip_pfsoc.c b/hw/riscv/microchip_pfsoc.c
> index e475b6d511..f10f55b488 100644
> --- a/hw/riscv/microchip_pfsoc.c
> +++ b/hw/riscv/microchip_pfsoc.c
> @@ -459,7 +459,6 @@ static void 
> microchip_icicle_kit_machine_init(MachineState *machine)
>      const MemMapEntry *memmap = microchip_pfsoc_memmap;
>      MicrochipIcicleKitState *s = MICROCHIP_ICICLE_KIT_MACHINE(machine);
>      MemoryRegion *system_memory = get_system_memory();
> -    MemoryRegion *mem_low = g_new(MemoryRegion, 1);
>      MemoryRegion *mem_low_alias = g_new(MemoryRegion, 1);
>      MemoryRegion *mem_high = g_new(MemoryRegion, 1);
>      MemoryRegion *mem_high_alias = g_new(MemoryRegion, 1);
> @@ -486,16 +485,13 @@ static void 
> microchip_icicle_kit_machine_init(MachineState *machine)
>      qdev_realize(DEVICE(&s->soc), NULL, &error_abort);
>  
>      /* Register RAM */
> -    memory_region_init_ram(mem_low, NULL, "microchip.icicle.kit.ram_low",
> -                           memmap[MICROCHIP_PFSOC_DRAM_LO].size,
> -                           &error_fatal);
>      memory_region_init_alias(mem_low_alias, NULL,
>                               "microchip.icicle.kit.ram_low.alias",
> -                             mem_low, 0,
> +                             machine->ram, 0,
>                               memmap[MICROCHIP_PFSOC_DRAM_LO_ALIAS].size);
>      memory_region_add_subregion(system_memory,
>                                  memmap[MICROCHIP_PFSOC_DRAM_LO].base,
> -                                mem_low);
> +                                machine->ram);
>      memory_region_add_subregion(system_memory,
>                                  memmap[MICROCHIP_PFSOC_DRAM_LO_ALIAS].base,
>                                  mem_low_alias);

looking at code it seems RAM is split between low and high regions,
so converting only low region is wrong.

I'd suggest something similar to 2dc9ce13d210 : taihu_405ep_init().
i.e. ms->ram should hold whole RAM that is split between low and high
using aliases.

> @@ -606,6 +602,7 @@ static void 
> microchip_icicle_kit_machine_class_init(ObjectClass *oc, void *data)
>                     MICROCHIP_PFSOC_COMPUTE_CPU_COUNT;
>      mc->min_cpus = MICROCHIP_PFSOC_MANAGEMENT_CPU_COUNT + 1;
>      mc->default_cpus = mc->min_cpus;
> +    mc->default_ram_id = "microchip.icicle.kit.ram_low";

given it is not versioned machine, so we don't have to worry about
cross version migration here,
so I'd use "microchip.icicle.kit.ram" for the name here
and currently used "microchip.icicle.kit.ram_low" for corresponding alias

>  
>      /*
>       * Map 513 MiB high memory, the mimimum required high memory size, 
> because