linux-kernel - Re: [PATCH] Use x2apic_supported() in the default_apic_id

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Message-ID: <4F627ED0.5080801@numascale.com>
Date:	Fri, 16 Mar 2012 00:44:16 +0100
From:	Steffen Persvold <sp@...ascale.com>
To:	Suresh Siddha <suresh.b.siddha@...el.com>
CC:	Yinghai Lu <yinghai@...nel.org>, Ingo Molnar <mingo@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Daniel J Blueman <daniel@...ascale-asia.com>,
	linux-kernel@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCH] Use x2apic_supported() in the default_apic_id_valid()
 function.

On 3/16/2012 00:33, Steffen Persvold wrote:
> On 3/16/2012 00:04, Suresh Siddha wrote:
>> On Thu, 2012-03-15 at 23:34 +0100, Steffen Persvold wrote:
>>> Is my understanding of your suggestion correct that in
>>> x2apic_phys/cluster.c we add the following apic_id_valid() function :
>>>
>>> static int x2apic_apic_id_valid(int apicid)
>>> {
>>> return x2apic_mode || (apicid< 255);
>>> }
>>
>> Steffen, We can have something like:
>>
>> static int x2apic_apic_id_valid(int apicid)
>> {
>> return 1;
>> }
>>
>> and
>>
>> static int xapic_apic_id_valid(int apicid)
>> {
>> return apicid< 255;
>> }
>>
>> If we have selected x2apic driver, then we know we are already in x2apic
>> mode. And also x2apic_uv_x need to use the x2apic version above.
>>
>
> If you specify "nox2apic" option, will it choose the xapic driver
> instead (and early enough) ? Otherwise I think we might break Yinghai's
> commit (a35fd28256e7736cc84af8931a16224f0bfaaf6c).
>

Answering myself here, my apologies, but yes it looks like both x2apic 
drivers will be de-activated if the "nox2apic" option is specified 
(x2apic_enabled() will return false).


Cheers,
Steffen
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