Messages in this thread | | | From | (Eric W. Biederman) | Date | Mon, 07 Jun 2010 18:10:12 -0700 | Subject | Re: [PATCH] x86/sfi: fix ioapic gsi range |
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"H. Peter Anvin" <hpa@zytor.com> writes:
> On 06/07/2010 05:24 PM, Eric W. Biederman wrote: >> Jacob Pan <jacob.jun.pan@linux.intel.com> writes: >> >>> SFI based platforms should have zero based gsi_base for IOAPICs found in SFI >>> tables. The current code sets gsi_base starting from 1 when registering ioapic. >>> The result is that Moorestown platform would have wrong mp_gsi_routing for each >>> ioapic. >> >> Yes starting at 1 is a bug. >> >>> Background: >>> In Moorestown/Medfield platforms, there is no legacy IRQs, all gsis and irqs >>> are one to one mapped, including those < 16. Specifically, IRQ0 and IRQ1 are >>> used for per-cpu timers. So without this patch, IOAPIC pin to IRQ mapping is >>> off by one. >> >> The patch looks mostly reasonable the comment is wrong. >> >> You may not use a 1-1 mapping if you don't have legacy irqs. Linux >> irqs 0-15 are the ISA irqs you may not use those irq numbers for >> something different on any architecture, but especially not on x86. >> The gsi numbers are firmware specific and you may treat however you want. >> >> Does the following patch work for you? >> >> It appears I goofed when it was pointed out that gsi_end was inclusive and >> didn't change the initialize. >> >> diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c >> index 33f3563..5de84e5 100644 >> --- a/arch/x86/kernel/apic/io_apic.c >> +++ b/arch/x86/kernel/apic/io_apic.c >> @@ -90,7 +90,7 @@ int nr_ioapics; >> struct mp_ioapic_gsi mp_gsi_routing[MAX_IO_APICS]; >> >> /* The last gsi number used */ >> -u32 gsi_end; >> +u32 gsi_end = -1; >> > > This seems like asking for signedness problems, especially since this is > used in range compares all the time. The real problem here is that > gsi_end is inclusive, which is almost always the wrong thing for the > endpoint of a range. Instead we should have the last number used plus > one; perhaps it should be called gsi_next or gsi_free.
That does sound better. Let me see if I can find a few minutes to implement it that way.
Eric
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