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Date: Fri, 08 Jan 2010 18:19:21 -0800 From: "H. Peter Anvin" <hpa@...or.com> To: Suresh Siddha <suresh.b.siddha@...el.com> CC: Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>, "ebiederm@...ssion.com" <ebiederm@...ssion.com>, Yinghai Lu <yinghai@...nel.org>, "Maciej W. Rozycki" <macro@...ux-mips.org>, LKML <linux-kernel@...r.kernel.org> Subject: Re: [patch] x86, apic: use 0x20 for the IRQ_MOVE_CLEANUP_VECTOR instead of 0x1f 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? > > -/* > - * 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. 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? -hpa -- H. Peter Anvin, Intel Open Source Technology Center I work for Intel. I don't speak on their behalf. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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