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Correct the number of IRQ0_VECTOR

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* IRQ0_VECTOR should equal to 0x30 ( ((FIRST_EXTERNAL_VECTOR + 16) & ~15 ) which FIRST_EXTERNAL_VECTOR is equal to 0x20
* mistype vecto_irq
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qinyungao 2022-12-05 13:58:18 +08:00
parent 54f9314a56
commit d9391ccbd8
1 changed files with 2 additions and 2 deletions
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Interrupts/linux-interrupts-8.md
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@ -97,7 +97,7 @@ Actual default maximum number of the legacy interrupts represented by the `NR_IR
#define NR_IRQS_LEGACY 16
```
In the loop we are accessing the `vecto_irq` per-cpu array with the `per_cpu` macro by the `IRQ0_VECTOR + i` index and write the legacy vector number there. The `IRQ0_VECTOR` macro defined in the [arch/x86/include/asm/irq_vectors.h](https://github.com/torvalds/linux/blob/16f73eb02d7e1765ccab3d2018e0bd98eb93d973/arch/x86/include/asm/irq_vectors.h) header file and expands to the `0x30`:
In the loop we are accessing the `vector_irq` per-cpu array with the `per_cpu` macro by the `IRQ0_VECTOR + i` index and write the legacy vector number there. The `IRQ0_VECTOR` macro defined in the [arch/x86/include/asm/irq_vectors.h](https://github.com/torvalds/linux/blob/16f73eb02d7e1765ccab3d2018e0bd98eb93d973/arch/x86/include/asm/irq_vectors.h) header file and expands to the `0x30`:
```C
#define FIRST_EXTERNAL_VECTOR 0x20
@ -105,7 +105,7 @@ In the loop we are accessing the `vecto_irq` per-cpu array with the `per_cpu` ma
#define IRQ0_VECTOR ((FIRST_EXTERNAL_VECTOR + 16) & ~15)
```
Why is `0x30` here? You can remember from the first [part](https://0xax.gitbook.io/linux-insides/summary/interrupts/linux-interrupts-1) of this chapter that first 32 vector numbers from `0` to `31` are reserved by the processor and used for the processing of architecture-defined exceptions and interrupts. Vector numbers from `0x30` to `0x3f` are reserved for the [ISA](https://en.wikipedia.org/wiki/Industry_Standard_Architecture). So, it means that we fill the `vector_irq` from the `IRQ0_VECTOR` which is equal to the `32` to the `IRQ0_VECTOR + 16` (before the `0x30`).
Why is `0x30` here? You can remember from the first [part](https://0xax.gitbook.io/linux-insides/summary/interrupts/linux-interrupts-1) of this chapter that first 32 vector numbers from `0` to `31` are reserved by the processor and used for the processing of architecture-defined exceptions and interrupts. Vector numbers from `0x30` to `0x3f` are reserved for the [ISA](https://en.wikipedia.org/wiki/Industry_Standard_Architecture). So, it means that we fill the `vector_irq` from the `IRQ0_VECTOR` which is equal to the `0x30` to the `IRQ0_VECTOR + 16` (before the `0x40`).
In the end of the `init_IRQ` function we can see the call of the following function: