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

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Date:	Mon, 02 Aug 2010 12:06:54 -0700
From:	Suresh Siddha <suresh.b.siddha@...el.com>
To:	Yinghai Lu <yinghai@...nel.org>
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 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?

thanks,
suresh

> 
> Signed-off-by: Yinghai Lu <yinghai@...nel.org>
> 
> ---
>  drivers/acpi/processor_core.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> Index: linux-2.6/drivers/acpi/processor_core.c
> ===================================================================
> --- linux-2.6.orig/drivers/acpi/processor_core.c
> +++ linux-2.6/drivers/acpi/processor_core.c
> @@ -69,7 +69,7 @@ static int map_x2apic_id(struct acpi_sub
>  	if (!(apic->lapic_flags & ACPI_MADT_ENABLED))
>  		return 0;
>  
> -	if (device_declaration && (apic->uid == acpi_id)) {
> +	if ((device_declaration || (acpi_id < 255)) && (apic->uid == acpi_id)) {
>  		*apic_id = apic->local_apic_id;
>  		return 1;
>  	}

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