linux-kernel - Re: MPS table vs ACPI

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Message-Id: <C8998C1F-0C0B-4B82-841A-16FD6829A90C@kernel.org>
Date:	Wed, 29 Jun 2011 17:40:37 -0700
From:	Yinghai <yinghai@...nel.org>
To:	sreenivasa reddy berahalli <sreenivasa-reddy-berahalli@...com>
Cc:	"tglx@...utronix.de" <tglx@...utronix.de>,
	"mingo@...hat.com" <mingo@...hat.com>,
	"hpa@...or.com" <hpa@...or.com>, "x86@...nel.org" <x86@...nel.org>,
	Feng Tang <feng.tang@...ux.intel.com>,
	"ebiederm@...ssion.com" <ebiederm@...ssion.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: MPS table vs ACPI



On Jun 29, 2011, at 3:32 PM, sreenivasa reddy berahalli <sreenivasa-reddy-berahalli@...com> wrote:

> Hello All,
> 
> Recent interaction with BIOS teams within in my Organization left me
> wondering if MP table spec from Intel is no more a mandatory one
> http://www.intel.com/design/pentium/datashts/24201606.pdf
> 
> Section #8.4.5 http://www.intel.com/Assets/PDF/manual/253668.pdf
> Talks as ACPI or MPS table.
> That means BIOS can report through ACPI tables only.
> 
> I looked through x86 boot sequence and notice Linux scanning for MPS
> table in below locations and Linux doesn't seem to go further without
> MPS table or doesn't know how to live with ACPI only.
> 1) Scan the bottom 1K for a signature
> 2) Scan the top 1K of base RAM
> 3) Scan the 64K of bios

Have one system with x2apic pre-enabled in bios, and it does not have mps table from bios. At least 2.6.32 based distribution kernel works well.
Current kernel works well too if you have acpi enabled in kernel.

Mptable assume apicid is 8 bits

Thanks

Yinghai--
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