Subject: Re: [PATCH 14/21] i386 Apm is on cpu zero only
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: Zachary Amsden <zach@vmware.com>
Cc: Ingo Molnar <mingo@elte.hu>, Andrew Morton <akpm@osdl.org>,
       Chris Wright <chrisw@osdl.org>, Linus Torvalds <torvalds@osdl.org>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       Virtualization Mailing List <virtualization@lists.osdl.org>,
       "H. Peter Anvin" <hpa@zytor.com>,
       Zwane Mwaikambo <zwane@arm.linux.org.uk>,
       Martin Bligh <mbligh@mbligh.org>,
       Pratap Subrahmanyam <pratap@vmware.com>,
       Christopher Li <chrisl@vmware.com>,
       "Eric W. Biederman" <ebiederm@xmission.com>
In-Reply-To: <43709FD7.1030905@vmware.com>
References: <200511080433.jA84Xwm7009921@zach-dev.vmware.com>
	 <20051108073315.GE28201@elte.hu>  <43709FD7.1030905@vmware.com>
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Date: Tue, 08 Nov 2005 13:54:51 +0000
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On Maw, 2005-11-08 at 04:53 -0800, Zachary Amsden wrote:
> Can't hurt, and APM is largely obsolete because of ACPI, so I'm only 
> concerned with trimming and keeping adequate protection of the kernel 
> from APM code while maintaining correctness.  I don't have a nice set of 
> old machines with enough wacky APM BIOSen to validate that unpinning the 
> CPU is ok.

A large number of SMP machines, probably the majority of APM based ones
require that APM calls occur on CPU#0. As I understand it from a BIOS
engineer involved in debugging that problem Redmond always does APM from
CPU #0 and may even guarantee it.

Alan

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