linux-kernel - Re: [PATCH 9/9] x86/apic: support moorestown interrupt subsystem

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Date:	Fri, 26 Jun 2009 16:46:24 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	"Pan\, Jacob jun" <jacob.jun.pan@...el.com>
Cc:	"linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>,
	"H. Peter Anvin" <hpa@...ux.intel.com>
Subject: Re: [PATCH 9/9] x86/apic: support moorestown interrupt subsystem

"Pan, Jacob jun" <jacob.jun.pan@...el.com> writes:

>>-----Original Message-----
>>From: Eric W. Biederman [mailto:ebiederm@...ssion.com]
>>Sent: Friday, June 26, 2009 12:42 PM
>>To: Pan, Jacob jun
>>Cc: linux-kernel@...r.kernel.org; H. Peter Anvin
>>Subject: Re: [PATCH 9/9] x86/apic: support moorestown interrupt subsystem
>>
>>"Pan, Jacob jun" <jacob.jun.pan@...el.com> writes:
>>
>>>>>From 82d64ca4f963d2e205326534aff0c77d9bfa5858 Mon Sep 17 00:00:00 2001
>>> From: Jacob Pan <jacob.jun.pan@...el.com>
>>> Date: Fri, 12 Jun 2009 02:16:05 -0700
>>> Subject: [PATCH] x86/apic: support moorestown interrupt subsystem
>>>
>>> This patch uses platform flags to selectively enable apic related setup
>>> code.
>>>
>>> Since moorestown does not have legacy timer or PIC, the only system
>>> timer irqs are routed via ioapic. Early timer ioapic enabling is also
>>> added to allow boot time timing services.
>>
>>This patch is horribly wrong.   We should not have a moorestown specific
>>hack  we should not do early timer ioapic on everything that supports
>>it which is most x86 machines since apics became common.
>>
> [[JPAN]] maybe I misunderstood. But I am doing the special early timer ioapic
> setup in x86_quirks, so it is not for every platform.
>
>>At which point moorestown support should just be a little work somewhere
>>in the table parsers.
>>
> [[JPAN]] can you elaborate a little? I was hoping to move APIC initialization earlier so that I don't have to have the special treatment for system timer.
> But it seems require early memory allocator.

We have early memory allocators.  And we are not talking super
early.  Just at the point init_IRQ is called.

> [[JPAN]] Moorestown does not have 8259, even IOAPIC is emulated by FW. Are you
> saying we should try to completely separate 8259 instead of use if(8259) here
> and there in the IOAPIC code? T

Yes, completely separate out the 8259.  I believe that complete
separation will come for free if you move the ioapic earlier.

What kind of PIC is native?

Eric
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