The vectors between FIRST_SYSTEM_VECTOR and NR_VECTORS are special IRQ
vectors used by the SMP architecture. But, if X86_LOCAL_APIC=n, it will
not be used, and the FIRST_SYSTEM_VECTOR is equal to NR_VECTORS.
idt_setup_apic_and_irq_gates() didn't notice that, which make the code
a little complex.
Remove the code of the X86_LOCAL_APIC=n case to simplify it.
Signed-off-by: Dou Liyang <[email protected]>
---
arch/x86/kernel/idt.c | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)
diff --git a/arch/x86/kernel/idt.c b/arch/x86/kernel/idt.c
index 2c3a1b4294eb..8b4174890706 100644
--- a/arch/x86/kernel/idt.c
+++ b/arch/x86/kernel/idt.c
@@ -317,15 +317,16 @@ void __init idt_setup_apic_and_irq_gates(void)
set_intr_gate(i, entry);
}
- for_each_clear_bit_from(i, system_vectors, NR_VECTORS) {
+ /*
+ * If X86_LOCAL_APIC=n, the FIRST_SYSTEM_VECTOR is equal to NR_VECTORS
+ * Just consider the X86_LOCAL_APIC=y case
+ */
#ifdef CONFIG_X86_LOCAL_APIC
+ for_each_clear_bit_from(i, system_vectors, NR_VECTORS) {
set_bit(i, system_vectors);
set_intr_gate(i, spurious_interrupt);
-#else
- entry = irq_entries_start + 8 * (i - FIRST_EXTERNAL_VECTOR);
- set_intr_gate(i, entry);
-#endif
}
+#endif
}
/**
--
2.14.3
On Thu, 26 Apr 2018, Dou Liyang wrote:
> The vectors between FIRST_SYSTEM_VECTOR and NR_VECTORS are special IRQ
> vectors used by the SMP architecture. But, if X86_LOCAL_APIC=n, it will
> not be used, and the FIRST_SYSTEM_VECTOR is equal to NR_VECTORS.
Correct, but that function has nothing to do with FIRST_SYSTEM_VECTOR.
> diff --git a/arch/x86/kernel/idt.c b/arch/x86/kernel/idt.c
> index 2c3a1b4294eb..8b4174890706 100644
> --- a/arch/x86/kernel/idt.c
> +++ b/arch/x86/kernel/idt.c
> @@ -317,15 +317,16 @@ void __init idt_setup_apic_and_irq_gates(void)
> set_intr_gate(i, entry);
> }
>
> - for_each_clear_bit_from(i, system_vectors, NR_VECTORS) {
> + /*
> + * If X86_LOCAL_APIC=n, the FIRST_SYSTEM_VECTOR is equal to NR_VECTORS
> + * Just consider the X86_LOCAL_APIC=y case
> + */
> #ifdef CONFIG_X86_LOCAL_APIC
> + for_each_clear_bit_from(i, system_vectors, NR_VECTORS) {
> set_bit(i, system_vectors);
> set_intr_gate(i, spurious_interrupt);
> -#else
> - entry = irq_entries_start + 8 * (i - FIRST_EXTERNAL_VECTOR);
> - set_intr_gate(i, entry);
> -#endif
> }
> +#endif
That change breaks the LOCAL_APIC=n case in a subtle way. What the function
does is to set _ALL_ entries starting from FIRST_EXTERNAL_VECTOR up to
NR_VECTORS in the IDT to a known target, except those which are already
occupied by a system vector.
So for APIC=y this sets them to: spurious vector and for APIC=n it sets it
to the corresppnding vector entry. You remove the latter...
Thanks,
tglx
Hi Thomas,
At 05/19/2018 08:32 PM, Thomas Gleixner wrote:
> On Thu, 26 Apr 2018, Dou Liyang wrote:
>
>> The vectors between FIRST_SYSTEM_VECTOR and NR_VECTORS are special IRQ
>> vectors used by the SMP architecture. But, if X86_LOCAL_APIC=n, it will
>> not be used, and the FIRST_SYSTEM_VECTOR is equal to NR_VECTORS.
>
> Correct, but that function has nothing to do with FIRST_SYSTEM_VECTOR.
>
Oops, sorry, when I reread, my changelog even made me misunderstand.
the patch hided it.
void __init idt_setup_apic_and_irq_gates(void)
...
for_each_clear_bit_from(i, system_vectors, FIRST_SYSTEM_VECTOR)
^^^^^^^^^^^^^^^^^^^
...
for_each_clear_bit_from(i, system_vectors, NR_VECTORS)
What I want to say is:
In the APIC=n system, the FIRST_SYSTEM_VECTOR is equal to
NR_VECTORS, So all entries has been set by
for_each_clear_bit_from(i, system_vectors, FIRST_SYSTEM_VECTOR)
...
the following setup code for APIC=n is redundant. Just setup gates for
APIC=y.
If it is OK, I will send v2.
Thanks,
dou
>> diff --git a/arch/x86/kernel/idt.c b/arch/x86/kernel/idt.c
>> index 2c3a1b4294eb..8b4174890706 100644
>> --- a/arch/x86/kernel/idt.c
>> +++ b/arch/x86/kernel/idt.c
>> @@ -317,15 +317,16 @@ void __init idt_setup_apic_and_irq_gates(void)
>> set_intr_gate(i, entry);
>> }
>>
>> - for_each_clear_bit_from(i, system_vectors, NR_VECTORS) {
>> + /*
>> + * If X86_LOCAL_APIC=n, the FIRST_SYSTEM_VECTOR is equal to NR_VECTORS
>> + * Just consider the X86_LOCAL_APIC=y case
>> + */
>> #ifdef CONFIG_X86_LOCAL_APIC
>> + for_each_clear_bit_from(i, system_vectors, NR_VECTORS) {
>> set_bit(i, system_vectors);
>> set_intr_gate(i, spurious_interrupt);
>> -#else
>> - entry = irq_entries_start + 8 * (i - FIRST_EXTERNAL_VECTOR);
>> - set_intr_gate(i, entry);
>> -#endif
>> }
>> +#endif
>
> That change breaks the LOCAL_APIC=n case in a subtle way. What the function
> does is to set _ALL_ entries starting from FIRST_EXTERNAL_VECTOR up to
> NR_VECTORS in the IDT to a known target, except those which are already
> occupied by a system vector.
>
> So for APIC=y this sets them to: spurious vector and for APIC=n it sets it
> to the corresppnding vector entry. You remove the latter...
> > Thanks,
>
> tglx
>
>
>
>
On Tue, 22 May 2018, Dou Liyang wrote:
> Hi Thomas,
>
> At 05/19/2018 08:32 PM, Thomas Gleixner wrote:
> > On Thu, 26 Apr 2018, Dou Liyang wrote:
> >
> > > The vectors between FIRST_SYSTEM_VECTOR and NR_VECTORS are special IRQ
> > > vectors used by the SMP architecture. But, if X86_LOCAL_APIC=n, it will
> > > not be used, and the FIRST_SYSTEM_VECTOR is equal to NR_VECTORS.
> >
> > Correct, but that function has nothing to do with FIRST_SYSTEM_VECTOR.
> >
>
> Oops, sorry, when I reread, my changelog even made me misunderstand.
> the patch hided it.
>
> void __init idt_setup_apic_and_irq_gates(void)
> ...
> for_each_clear_bit_from(i, system_vectors, FIRST_SYSTEM_VECTOR)
> ^^^^^^^^^^^^^^^^^^^
> ...
> for_each_clear_bit_from(i, system_vectors, NR_VECTORS)
>
> What I want to say is:
>
> In the APIC=n system, the FIRST_SYSTEM_VECTOR is equal to
> NR_VECTORS, So all entries has been set by
>
> for_each_clear_bit_from(i, system_vectors, FIRST_SYSTEM_VECTOR)
> ...
>
> the following setup code for APIC=n is redundant. Just setup gates for
> APIC=y.
>
> If it is OK, I will send v2.
Right you are. I got confused ....