LIU Zhiwei <zhiwei_liu@c-sky.com> 於 2021年6月28日 週一 下午4:12寫道：

On 2021/6/28 下午4:07, Frank Chang wrote:

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?)

Once we have a talk on tech-fast-interrupt. The chair of fast interrupt reply is:

"The first part (address 0x0000-0x0FFF) which contains cliccfg/clicinfo/clicinttrig should be global since only one copy of the configuration setting is enough.
On the other hand, the latter part (0x1000-0x4FFF) which contains control bits for individual interrupt should be one copy per hart"

Hmm... interesting, that's probably something I have missed.

and they didn't document this statement in the spec :(

But I think this statement has a contradiction against the system with multi-CLIC instances described in spec.

Does it imply that either:

  * I can only have one CLIC in the system, or

  * All CLIC instances must have the same configuration in the system.

The second one.

I think the CLIC instance here is just on the concept of logic,  like the current implementation. Furthermore, we can give
every logic CLIC instance a configurable memory region from the machine board in the near future.

Thanks,
Zhiwei

Do you have the link to this statement? I would like to take a look.

Thanks,

Frank Chang

Thanks,
Zhiwei

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;
+    }
+}
+