Re: [RFC PATCH 03/11] hw/intc: Add CLIC device

[Frank Chang <frank.chang@sifive.com>]

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LIU Zhiwei <zhiwei_liu@c-sky.com> 於 2021年6月28日 週一 下午4:03寫道：

>
> On 2021/6/28 下午3:49, Frank Chang wrote:
>
> LIU Zhiwei <zhiwei_liu@c-sky.com> 於 2021年6月28日 週一 下午3:40寫道：
>
>>
>> On 2021/6/28 下午3:23, Frank Chang wrote:
>>
>> LIU Zhiwei <zhiwei_liu@c-sky.com> 於 2021年6月28日 週一 下午3:17寫道：
>>
>>>
>>> On 2021/6/26 下午8:56, Frank Chang wrote:
>>>
>>> On Wed, Jun 16, 2021 at 10:56 AM LIU Zhiwei <zhiwei_liu@c-sky.com>
>>> wrote:
>>>
>>>>
>>>> On 6/13/21 6:10 PM, Frank Chang wrote:
>>>>
>>>> LIU Zhiwei <zhiwei_liu@c-sky.com> 於 2021年4月9日 週五 下午3:57寫道：
>>>>
>>>> +static void riscv_clic_realize(DeviceState *dev, Error **errp)
>>>>> +{
>>>>> +    RISCVCLICState *clic = RISCV_CLIC(dev);
>>>>> +    size_t harts_x_sources = clic->num_harts * clic->num_sources;
>>>>> +    int irqs, i;
>>>>> +
>>>>> +    if (clic->prv_s && clic->prv_u) {
>>>>> +        irqs = 3 * harts_x_sources;
>>>>> +    } else if (clic->prv_s || clic->prv_u) {
>>>>> +        irqs = 2 * harts_x_sources;
>>>>> +    } else {
>>>>> +        irqs = harts_x_sources;
>>>>> +    }
>>>>> +
>>>>> +    clic->clic_size = irqs * 4 + 0x1000;
>>>>> +    memory_region_init_io(&clic->mmio, OBJECT(dev), &riscv_clic_ops,
>>>>> clic,
>>>>> +                          TYPE_RISCV_CLIC, clic->clic_size);
>>>>> +
>>>>> +    clic->clicintip = g_new0(uint8_t, irqs);
>>>>> +    clic->clicintie = g_new0(uint8_t, irqs);
>>>>> +    clic->clicintattr = g_new0(uint8_t, irqs);
>>>>> +    clic->clicintctl = g_new0(uint8_t, irqs);
>>>>> +    clic->active_list = g_new0(CLICActiveInterrupt, irqs);
>>>>> +    clic->active_count = g_new0(size_t, clic->num_harts);
>>>>> +    clic->exccode = g_new0(uint32_t, clic->num_harts);
>>>>> +    clic->cpu_irqs = g_new0(qemu_irq, clic->num_harts);
>>>>> +    sysbus_init_mmio(SYS_BUS_DEVICE(dev), &clic->mmio);
>>>>> +
>>>>> +    /* Allocate irq through gpio, so that we can use qtest */
>>>>> +    qdev_init_gpio_in(dev, riscv_clic_set_irq, irqs);
>>>>> +    qdev_init_gpio_out(dev, clic->cpu_irqs, clic->num_harts);
>>>>> +
>>>>> +    for (i = 0; i < clic->num_harts; i++) {
>>>>> +        RISCVCPU *cpu = RISCV_CPU(qemu_get_cpu(i));
>>>>>
>>>>
>>>> As spec says:
>>>>   Smaller single-core systems might have only a CLIC,
>>>>   while multicore systems might have a CLIC per-core and a single
>>>> shared PLIC.
>>>>   The PLIC xeip signals are treated as hart-local interrupt sources by
>>>> the CLIC at each core.
>>>>
>>>> It looks like it's possible to have one CLIC instance per core.
>>>>
>>>> If you want to delivery an interrupt to one hart, you should encode the
>>>> IRQ by the interrupt number
>>>> , the hart number and the interrupt target privilege, then set the irq.
>>>>
>>>> I think how to calculate the hart number is the task of PLIC and it can
>>>> make use of "hartid-base"
>>>> to calculate it.
>>>>
>>>> Thanks,
>>>> Zhiwei
>>>>
>>>
>>> Hi Zhiwei,
>>>
>>> What I mean is if there are multiple CLIC instances, each per core (CLIC
>>> spec allows that).
>>> If you try to bind CLIC with CPU index start from 0,
>>> it will be impossible for CLIC instance to bind CPU from index other
>>> than 0.
>>>
>>> For example, for 4 cores system, it's possible to have 4 CLIC instances:
>>>   * CLIC 0 binds to CPU 0
>>>   * CLIC 1 binds to CPU 1
>>>   * CLIC 2 binds to CPU 2
>>>   * CLIC 3 binds to CPU 3
>>>
>>> and that's why I said it's possible to pass an extra "hartid-base" just
>>> like PLIC.
>>> I know most of hardid are calculated by the requesing address, so most
>>> hartid usages should be fine.
>>> But I saw two places using qemu_get_cpu(),
>>>
>>> which may cause the problem for the scenario I describe above:
>>> i.e. riscv_clic_next_interrupt() and riscv_clic_realize() as my original
>>> reply.
>>>
>>> So what's the problem here?
>>>
>>> Currently all cores share the same CLIC instance. Do you want to give
>>> each core  a CLIC instance?
>>>
>> Yes, that's what I mean, which should be supported as what spec says[1]:
>>   The CLIC complements the PLIC. Smaller single-core systems might have
>> only a CLIC,
>>   while multicore systems might have *a CLIC per-core* and a single
>> shared PLIC.
>>   The PLIC xeip signals are treated as hart-local interrupt sources by
>> the CLIC at each core.
>>
>> [1]
>> https://github.com/riscv/riscv-fast-interrupt/blob/646310a5e4ae055964b4680f12c1c04a7cc0dd56/clic.adoc#12-clic-versus-plic
>>
>> Thanks,
>> Frank Chang
>>
>>
>> If we give each core a CLIC instance, it is not convenient to access the
>> shared memory, such as 0x0-0x1000.
>> Which CLIC instance should contain this memory region?
>>
> What do you mean by: "access the shared memory" here?
>
> It means the cliccfg or clicinfo which  should be shared by all CLIC
> instances.
>
If there are multiple CLIC instances, shouldn't they have their own base
addresses?
So I do not understand how cliccfg and clicinfo would be shared by all CLIC
instances. (Or they should?)
Each CLIC instance will manage its own cliccfg and clicinfo.

Thanks,
Frank Chang

Thanks,
> Zhiwei
>
> I thought the memory region is defined during CLIC's creation?
> So it should depend on the platform that creates CLIC instances.
>
> Thanks,
> Frank Chang
>
>
>> Thanks,
>> Zhiwei
>>
>>
>>> Thanks,
>>> Zhiwei
>>>
>> Regards,
>>> Frank Chang
>>>
>>>
>>>> However if you try to bind CPU reference start from index i = 0.
>>>> It's not possible for each per-core CLIC to bind their own CPU instance
>>>> in multicore system
>>>> as they have to bind from CPU 0.
>>>>
>>>> I'm not sure if we add a new "hartid-base" property just like what
>>>> SiFive PLIC is
>>>> implemented would be a good idea or not.
>>>>
>>>>
>>>> Regards,
>>>> Frank Chang
>>>>
>>>>
>>>>> +        qemu_irq irq = qemu_allocate_irq(riscv_clic_cpu_irq_handler,
>>>>> +                                         &cpu->env, 1);
>>>>> +        qdev_connect_gpio_out(dev, i, irq);
>>>>> +        cpu->env.clic = clic;
>>>>> +    }
>>>>> +}
>>>>> +
>>>>>
>>>>>
>>>>>

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