This is the boot message of the virtual machine related to IRQ.

[    0.000000] NR_IRQS: 64, nr_irqs: 64, preallocated irqs: 0

[    0.000000] GICv3: 224 SPIs implemented

[    0.000000] GICv3: 0 Extended SPIs implemented

[    0.000000] GICv3: Distributor has no Range Selector support

[    0.000000] GICv3: 16 PPIs implemented

[    0.000000] GICv3: no VLPI support, no direct LPI support

[    0.000000] GICv3: CPU0: found redistributor 0 region 0:0x00000000080a0000

Somehow the NR_IRQS is 64.

So I tried using SPI 15 which was not assigned. (32 internal IRQs + 15 < 64) and now request_irq returns 0.

So this irq_desc problem was solved(?) for now. (I don’t know why this is so small when CONFIG_SPARSE_IRQS=y).

And still the handler is not called even when I set qemu_set_irq.

_____________________________________________
From: Chan Kim <ckim@etri.re.kr>
Sent: Wednesday, April 6, 2022 10:46 AM
To: 'qemu-discuss' <qemu-discuss@nongnu.org>; kernelnewbies@kernelnewbies.org
Subject: irq_desc not found for my interrupt number during request_irq (radix tree of irq_desc has only 64 entries..)

Hello all,

I'm doing an linux driver and application test on a qemu arm64 virtual machine.

My virtual machine is slightly modified version of arm 'virt' machine and it has our device model included.

When I do request_irq for INTID 208 (SPI 176) in linux on my arm64 virtual machine, it returns -EINVAL.

I poked into that function and found the desc is returning NULL in function request_threaded_irq.

int request_threaded_irq(unsigned int irq, irq_handler_t handler,

             irq_handler_t thread_fn, unsigned long irqflags,

             const char *devname, void *dev_id)

{

    struct irqaction *action;

    struct irq_desc *desc;

    int retval;

...

desc = irq_to_desc(irq);

    if (!desc)

        return -EINVAL;

...

}

and irq_to_desc is supposed to return an irq_desc from the irq_radix_tree as shown below.

struct irq_desc *irq_to_desc(unsigned int irq)

{

    return radix_tree_lookup(&irq_desc_tree, irq);

}

void *radix_tree_lookup(const struct radix_tree_root *root, unsigned long index)

{

    return __radix_tree_lookup(root, index, NULL, NULL);

}

void *__radix_tree_lookup(const struct radix_tree_root *root,

              unsigned long index, struct radix_tree_node **nodep,

              void __rcu ***slotp)

{

    struct radix_tree_node *node, *parent;

    unsigned long maxindex;

    void __rcu **slot;

 restart:

    parent = NULL;

    slot = (void __rcu **)&root->xa_head;

    radix_tree_load_root(root, &node, &maxindex);

    if (index > maxindex)

        return NULL;

...

}

and I found my request index is 208 but the maxindex of the radix tree is 63.

So it looks like the radix tree of irq_desc has been set to have maximum 64 irq_descs.

Where and how can I set this radix tree size?

I looked at qemu's hw/arm/ab21q-build-acpi.c for MADT or DSDT table parts but couldn't find what to add.

I have my devices address range and irq added in the DSDT and MADT.

static void

build_dsdt(GArray *table_data, BIOSLinker *linker, Ab21qMachineState *vms)

{

...

acpi_dsdt_add_axpu(scope, &memmap[AB21Q_AXPU],

                       (irqmap[AB21Q_AXPU] + ARM_SPI_BASE));

...

}

static void acpi_dsdt_add_axpu(Aml *scope, const MemMapEntry *axpu_memmap,

                                           uint32_t irq)

{

    Aml *dev = aml_device("AXPU");

    aml_append(dev, aml_name_decl("_HID", aml_string("AXPU0011")));

    aml_append(dev, aml_name_decl("_UID", aml_int(0)));

    Aml *crs = aml_resource_template();

    aml_append(crs, aml_memory32_fixed(axpu_memmap->base,

                                       axpu_memmap->size, AML_READ_WRITE));

    aml_append(crs,

               aml_interrupt(AML_CONSUMER, AML_LEVEL, AML_ACTIVE_HIGH,

                             AML_EXCLUSIVE, &irq, 1));

    aml_append(dev, aml_name_decl("_CRS", crs));

    aml_append(scope, dev);

}

I'm not sure if I can just use _HID value as "AXPU0011".

If you see anything wrong and have a suggestion, please tell me.

Thank you!

Chan Kim