linux-kernel - Re: [patch 00/26] x64, x2apic/intr-remap: Interrupt-remapping and x2apic support

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Message-ID: <86802c440807112317h23118e29j51113a052720d8db@mail.gmail.com>
Date:	Fri, 11 Jul 2008 23:17:02 -0700
From:	"Yinghai Lu" <yhlu.kernel@...il.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	"Suresh Siddha" <suresh.b.siddha@...el.com>,
	"Ingo Molnar" <mingo@...e.hu>, "hpa@...or.com" <hpa@...or.com>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"arjan@...ux.intel.com" <arjan@...ux.intel.com>,
	"andi@...stfloor.org" <andi@...stfloor.org>,
	"jbarnes@...tuousgeek.org" <jbarnes@...tuousgeek.org>,
	"steiner@....com" <steiner@....com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"jeremy@...p.org" <jeremy@...p.org>
Subject: Re: [patch 00/26] x64, x2apic/intr-remap: Interrupt-remapping and x2apic support

On Fri, Jul 11, 2008 at 8:52 PM, Eric W. Biederman
<ebiederm@...ssion.com> wrote:
> "Yinghai Lu" <yhlu.kernel@...il.com> writes:
>
>> 1. wonder if x2apic can be use with uniprocessor.
>>
>> in APIC_init_uniprocessor, it will try to enable x2apic, but later
>>
>> apic_write(APIC_ID, SET_APIC_ID(boot_cpu_physical_apicid));
>>
>> but SET_APIC_ID is still for xapic version. so need to GET_APIC_ID,
>> SET_APIC_ID for different
>> genapic like 32bit.
>>
>> 2 check_x2apic is called in setup_arch, but it only set apic_ops,
>> and genapic still not changed, aka apic_flat...
>> wonder if you need to call setup_apic_routing to set genapic.
>>
>> otherwise read_apic_id could have use the one from apic_flat....need
>> to shift......
>>
>> 3.or move read_apic_id to apic_ops intead...together with GET_APIC_ID too.
>> but 32bit version seems like to put GET_APIC_ID with genapic...
>>
>> which one is better? 2 or 3
>
> Z finish untangle SMP support from apic initialization and move the apic
> initialization up into init_IRQ.
>
> That is better but is likely the wrong short term approach.

plan to add get_apic_id(x) into 64bit genapic, and will use
#define GET_APIC_ID(x) genapic->get_apic_id(x)
#define read_apic_id() GET_APIC_ID(apic_read(APIC_ID))

so it is identical to 32bit, and we smooth the merging of 32/64 apic code

also read the x2APIC spec pdf, it doesn't say anything about interrupt
remapping...need to be used with x2apic...

YH
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