linux-kernel - Re: [RFC] [PATCH 10/16] x86

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Message-ID: <20061113193447.GB13832@in.ibm.com>
Date:	Mon, 13 Nov 2006 14:34:47 -0500
From:	Vivek Goyal <vgoyal@...ibm.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Andi Kleen <ak@...e.de>,
	linux kernel mailing list <linux-kernel@...r.kernel.org>,
	Reloc Kernel List <fastboot@...ts.osdl.org>, akpm@...l.org,
	hpa@...or.com, magnus.damm@...il.com, lwang@...hat.com,
	dzickus@...hat.com, pavel@...e.cz,
	"Rafael J. Wysocki" <rjw@...k.pl>
Subject: Re: [RFC] [PATCH 10/16] x86_64: 64bit PIC ACPI wakeup

On Mon, Nov 13, 2006 at 12:21:05PM -0700, Eric W. Biederman wrote:
> Andi Kleen <ak@...e.de> writes:
> 
> >> This code (verify_cpu) is called while we are still in real mode. So it has
> >> to be present in low 1MB. Now in trampoline has been designed to switch to
> >> 64bit mode and then jump to the kernel hence kernel can be loaded anywhere
> >> even beyond (4G). So if we move this code into say arch/x86_64/kernel/head.S
> >> then we can't even call it.
> >
> > I didn't mean to call it. Just #include it from a common file
> 
> I believe the duplication winds up happening in setup.S
> 

Yes. So boot cpu code in setup.S is also doing these checks. So one 
of the options is that I create a new file says verify_cpu.S and this
code can be shared by setup.S, trampoline.S and wakeup.S.

Or, I can simply drop the verify_cpu bit from trampoline.S and wakeup.S.
This looks like a non-essential bit and in the past we did not perform
these checks in trampoline.S and wakeup.S

At this point of time, I will prefer to go with second option of dropping
extended checks in trampoline.S and wakeup.S to keep things simple.

Does that make sense?

Thanks
Vivek

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