Messages in this thread |  | | Subject | Re: [patch] x86, apic: use 0x20 for the IRQ_MOVE_CLEANUP_VECTOR instead of 0x1f | From | Suresh Siddha <> | Date | Mon, 11 Jan 2010 14:53:38 -0800 |
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On Fri, 2010-01-08 at 18:19 -0800, H. Peter Anvin wrote: > On 01/08/2010 06:09 PM, Suresh Siddha wrote: > > > > So change the IRQ_MOVE_CLEANUP_VECTOR to 0x20 and allow 0x21-0x2f to be used > > for device interrupts. 0x30-0x3f will be used for ISA interrupts (these > > also can be migrated in the context of IOAPIC and hence need to be at a higher > > priority level than IRQ_MOVE_CLEANUP_VECTOR). > > > > You're referring to when they're accessed as IOAPIC interrupts as > opposed to ExtInt interrupts?
yes.
> > -/* > > - * First APIC vector available to drivers: (vectors 0x30-0xee). We > > - * start allocating at 0x31 to spread out vectors evenly between > > - * priority levels. (0x80 is the syscall vector) > > - */ > > -#define FIRST_DEVICE_VECTOR (IRQ15_VECTOR + 1) > > -#define VECTOR_OFFSET_START 1 > > - > > #define NR_VECTORS 256 > > > > #define FPU_IRQ 13 > > diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c > > index d5bfa29..5c090a1 100644 > > --- a/arch/x86/kernel/apic/io_apic.c > > +++ b/arch/x86/kernel/apic/io_apic.c > > @@ -1162,8 +1162,8 @@ __assign_irq_vector(int irq, struct irq_cfg *cfg, const struct cpumask *mask) > > * Also, we've got to be careful not to trash gate > > * 0x80, because int 0x80 is hm, kind of importantish. ;) > > */ > > - static int current_vector = FIRST_DEVICE_VECTOR + VECTOR_OFFSET_START; > > - static int current_offset = VECTOR_OFFSET_START % 8; > > + static int current_vector = FIRST_DEVICE_VECTOR; > > + static int current_offset = 0; > > unsigned int old_vector; > > int cpu, err; > > cpumask_var_t tmp_mask; > > > > I'm not entirely sure I like losing this bit, even though it isn't > really necessary with your changes (VECTOR_OFFSET_START would be 0). > I'm afraid we might end up with the same buglet being "reinvented" later.
Ok. We should be able to retain that bit. I will send another version shortly.
> However, my most serious concern with this patch is that there is a > fairly significant change due to this patch, which is that the legacy > IRQ vectors now fall *inside* the FIRST_DEVICE_VECTOR range. This isn't > a bad thing -- in fact, it is fundamentally the right thing to do > especially once we consider platforms which *don't* have the legacy IRQs > -- but it makes me scared of unexpected behavior changes as a result. > If you feel confident that that is not the case, could you outline why > it shouldn't be a problem?
In irqinit.c, we statically pre-assign the per-cpu vector to irq mappings (vector_irq) for all the legacy IRQ vectors. Similarly irq_cfg is statically initialized for legacy IRQ's in io_apic.c. So we won't be able to use this space for anything else.
thanks, suresh
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