linux-kernel - Re: [PATCH] acpi: x2apic entry with uid

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Message-ID: <AANLkTi=HUTRqkj=zYV=5Z9fZAZa_sNmRanibaMLGrX0R@mail.gmail.com>
Date:	Mon, 2 Aug 2010 13:18:49 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	Suresh Siddha <suresh.b.siddha@...el.com>
Cc:	Len Brown <lenb@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: [PATCH] acpi: x2apic entry with uid < 255 could use processor 
	statement

On Mon, Aug 2, 2010 at 12:06 PM, Suresh Siddha
<suresh.b.siddha@...el.com> wrote:
> On Sat, 2010-07-31 at 07:51 +0100, Yinghai Lu wrote:
>> According to Intel x2apic spec page 46
>>
>> " The hand-off to
>> OSPM will have processor IDs in the range of 0 to 254 for xAPIC/x2APIC and 0 to 255
>> for SAPIC declared as either Processor() or Device() objects, but not both. Processor
>> IDs outside these ranges must be declared as Device() objects."
>>
>> So only check if Device is used when acpi_id >=255.
>>
>> that will help system with less 255 cpus, but some cpus apic id > 255,
>> still can use Processor statement instead of Device() objects.
>
> But the entries with apic_id < 255 are supposed to use local APIC
> structure and not local x2apic structure. So entries with apic id < 255
> must be processed using map_lapic_id() which doesn't have any
> device_declaration checks.
>
> Only for apic ids > 255, we use map_x2apic_id() which needs device
> declaration. So this patch is not needed. or Am I missing something?

it is acpi_id aka  Processor id.

the system has less than 255 cpus, but some cpus apic_id > 255.
BIOS have apic entries for apic_id < 255, and some x2apic entries for
apic_id > 255.

but BIOS still use Processor statement for all cpus.

Thanks

Yinghai
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