linux-kernel - Re: [PATCH] x86/sfi: fix ioapic gsi range

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Message-ID: <20100610014018.00001c23@unknown>
Date:	Thu, 10 Jun 2010 01:40:18 -0700
From:	jacob pan <jacob.jun.pan@...ux.intel.com>
To:	ebiederm@...ssion.com (Eric W. Biederman)
Cc:	Alan Cox <alan@...ux.intel.com>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	LKML <linux-kernel@...r.kernel.org>,
	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...e.hu>,
	Feng Tang <feng.tang@...el.com>,
	Len Brown <len.brown@...el.com>
Subject: Re: [PATCH] x86/sfi: fix ioapic gsi range

Eric W. Biederman Wed, 09 Jun 2010 16:44:11 -0700
>jacob pan <jacob.jun.pan@...ux.intel.com> writes:
>
>> [jacob pan] 
>>
>> In arch/x86/kernel/mrst.c we parse SFI MTMR table then
>> add timer irqs to mp_irqs. what is broken by this patch is
>> pin_2_irq() lookup for the legacy irq range since we want
>> NR_IRQS_LEGACY to be 0 on Moorestown. We do have the assumption that
>> mp_irqs from SFI is 1:1 mapped to IRQs.
>
>NR_IRQS_LEGACY is a constant of 16.
i know, what i meant is we want this to be a variable.
>
>> Doing this can fix the problem, but you mentioned you have to use
>> NR_IRQS_LEGACY, which i still don't understand.
>
>Looking at the code in io_apic.c there is a relatively clean way to
>handle this.  The actual concept in io_apic.c today is mp_bus_not_pci.
>
>So you just need to do:
>
>diff --git a/arch/x86/kernel/mrst.c b/arch/x86/kernel/mrst.c
>index e796448..9377fda 100644
>--- a/arch/x86/kernel/mrst.c
>+++ b/arch/x86/kernel/mrst.c
>@@ -242,4 +242,5 @@ void __init x86_mrst_early_setup(void)
> 	x86_init.mpparse.find_smp_config = x86_init_noop;
> 	x86_init.mpparse.get_smp_config = x86_init_uint_noop;
> 
>+	set_bit(0, mp_bus_not_pci);
> }
>
>
>Then you get treated as ISA for purposes of pin_2_irq, and everything
>is a pass through.  Since that seems to be what you want anyway I don't
>see a problem with that for now.
>
I think this may work better. Since we already assign srcbus = MP_ISA_BUS to 
use the mp_irqs, this may be more inline with the current code.
Thanks for the pointer.

But the nr_irqs_gsi would still be wrong for Moorestown if don't use legacy_pic
or some sort of runtime detection.

>Using legacy pic to even talk about this behavior is wrong as that is
>hardware abstraction and the presence or absence of an i8259 has
>nothing to do with the presence of ISA irqs and their descendants.
>
>Eric
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