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

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

Hi Bibo,

On 26/6/24 06:11, maobibo wrote:
> 
> 
> On 2024/6/5 上午10:15, Jiaxun Yang wrote:
>> It was missed out in previous commit.
>>
>> Fixes: b4a12dfc2132 ("hw/intc/loongarch_ipi: Rename as loongson_ipi")
>> Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
>> ---
>>   hw/intc/loongarch_ipi.c | 347 
>> ------------------------------------------------
>>   1 file changed, 347 deletions(-)


>> -static void loongarch_ipi_realize(DeviceState *dev, Error **errp)
>> -{
>> -    LoongArchIPI *s = LOONGARCH_IPI(dev);
>> -    SysBusDevice *sbd = SYS_BUS_DEVICE(dev);
>> -    int i;
>> -
>> -    if (s->num_cpu == 0) {
>> -        error_setg(errp, "num-cpu must be at least 1");
>> -        return;
>> -    }
>> -
>> -    memory_region_init_io(&s->ipi_iocsr_mem, OBJECT(dev), 
>> &loongarch_ipi_ops,
>> -                          s, "loongarch_ipi_iocsr", 0x48);
>> -
>> -    /* loongarch_ipi_iocsr performs re-entrant IO through ipi_send */
>> -    s->ipi_iocsr_mem.disable_reentrancy_guard = true;
>> -
>> -    sysbus_init_mmio(sbd, &s->ipi_iocsr_mem);
>> -
>> -    memory_region_init_io(&s->ipi64_iocsr_mem, OBJECT(dev),
>> -                          &loongarch_ipi64_ops,
>> -                          s, "loongarch_ipi64_iocsr", 0x118);
>> -    sysbus_init_mmio(sbd, &s->ipi64_iocsr_mem);
> It is different with existing implementation.
> 
> 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.
> 
> 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.

Since commit b4a12dfc2132 this file is not built/tested anymore:

-specific_ss.add(when: 'CONFIG_LOONGARCH_IPI', if_true: 
files('loongarch_ipi.c'))
+specific_ss.add(when: 'CONFIG_LOONGSON_IPI', if_true: 
files('loongson_ipi.c'))

We don't want to maintain dead code.

Regards,

Phil.