Re: [PATCH v3 1/4] hw/intc: Remove loongarch_ipi.c

["Jiaxun Yang" <jiaxun.yang@flygoat.com>]

在2024年6月26日六月 上午5:11，maobibo写道：
[...]
> It is different with existing implementation.
What do you mean? Isn't this the actual hardware behaviour?

>
> With hw/intc/loongson_ipi.c, every vcpu has one ipi_mmio_mem, however on 
> loongarch ipi machine, there is no ipi_mmio_mem memory region.
> So if machine has 256 vcpus, there will be 256 ipi_mmio_mem memory 
> regions. In function sysbus_init_mmio(), memory region can not exceed
> QDEV_MAX_MMIO (32).  With so many memory regions, it slows down memory
> region search speed also.
Ouch, never thought about that before, but I think we can control the
registration of sysbus_mmio with a device property or even ifdef so LoongArch
machine won't be affected.

For MIPS loongson3-virt machine, our CPU number is capped, so that won't
be a problem.

I'm currently travelling without access to my PC, I'll prepare a patch
as soon as I gain access again. Feel free to send a patch before me with
this approach if you desperately want to fix it.

>
> void sysbus_init_mmio(SysBusDevice *dev, MemoryRegion *memory)
> {
>      int n;
>
>      assert(dev->num_mmio < QDEV_MAX_MMIO);
>      n = dev->num_mmio++;
>      dev->mmio[n].addr = -1;
>      dev->mmio[n].memory = memory;
> }
>
> Can we revert this patch? We want to do production usable by real users 
> rather than show pure technology.

I don't really get your point, we have at leat 4 real users requesting SMP
support for loongson3-virt on gitlab issues, plus I need this to test
MIPS/Loongson64 SMP kernel.

If there is a problem with your use case, we can fix it. Why we do want to
remove the functionality when there is an easy fix?

It’s not only the features necessary for you that made QEMU an outstanding
project; it’s everything coming together that completes it.

Thanks
- Jiaxun
>
> Regards
> Bibo Mao
>
>> -
>> -    s->cpu = g_new0(IPICore, s->num_cpu);
>> -    if (s->cpu == NULL) {
>> -        error_setg(errp, "Memory allocation for ExtIOICore faile");
>> -        return;
>> -    }
>> -
>> -    for (i = 0; i < s->num_cpu; i++) {
>> -        qdev_init_gpio_out(dev, &s->cpu[i].irq, 1);
>> -    }
>> -}
>> -
>> -static const VMStateDescription vmstate_ipi_core = {
>> -    .name = "ipi-single",
>> -    .version_id = 2,
>> -    .minimum_version_id = 2,
>> -    .fields = (const VMStateField[]) {
>> -        VMSTATE_UINT32(status, IPICore),
>> -        VMSTATE_UINT32(en, IPICore),
>> -        VMSTATE_UINT32(set, IPICore),
>> -        VMSTATE_UINT32(clear, IPICore),
>> -        VMSTATE_UINT32_ARRAY(buf, IPICore, IPI_MBX_NUM * 2),
>> -        VMSTATE_END_OF_LIST()
>> -    }
>> -};
>> -
>> -static const VMStateDescription vmstate_loongarch_ipi = {
>> -    .name = TYPE_LOONGARCH_IPI,
>> -    .version_id = 2,
>> -    .minimum_version_id = 2,
>> -    .fields = (const VMStateField[]) {
>> -        VMSTATE_STRUCT_VARRAY_POINTER_UINT32(cpu, LoongArchIPI, num_cpu,
>> -                         vmstate_ipi_core, IPICore),
>> -        VMSTATE_END_OF_LIST()
>> -    }
>> -};
>> -
>> -static Property ipi_properties[] = {
>> -    DEFINE_PROP_UINT32("num-cpu", LoongArchIPI, num_cpu, 1),
>> -    DEFINE_PROP_END_OF_LIST(),
>> -};
>> -
>> -static void loongarch_ipi_class_init(ObjectClass *klass, void *data)
>> -{
>> -    DeviceClass *dc = DEVICE_CLASS(klass);
>> -
>> -    dc->realize = loongarch_ipi_realize;
>> -    device_class_set_props(dc, ipi_properties);
>> -    dc->vmsd = &vmstate_loongarch_ipi;
>> -}
>> -
>> -static void loongarch_ipi_finalize(Object *obj)
>> -{
>> -    LoongArchIPI *s = LOONGARCH_IPI(obj);
>> -
>> -    g_free(s->cpu);
>> -}
>> -
>> -static const TypeInfo loongarch_ipi_info = {
>> -    .name          = TYPE_LOONGARCH_IPI,
>> -    .parent        = TYPE_SYS_BUS_DEVICE,
>> -    .instance_size = sizeof(LoongArchIPI),
>> -    .class_init    = loongarch_ipi_class_init,
>> -    .instance_finalize = loongarch_ipi_finalize,
>> -};
>> -
>> -static void loongarch_ipi_register_types(void)
>> -{
>> -    type_register_static(&loongarch_ipi_info);
>> -}
>> -
>> -type_init(loongarch_ipi_register_types)
>>

-- 
- Jiaxun