linux-kernel - Re: [PATCH] x86: Call __va() to get trampoline

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Message-ID: <4B19B680.9050700@zytor.com>
Date:	Fri, 04 Dec 2009 17:25:20 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Rakib Mullick <rakib.mullick@...il.com>,
	"Cihula, Joseph" <joseph.cihula@...el.com>,
	Shane Wang <shane.wang@...el.com>
CC:	Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>, x86@...nel.org
Subject: Re: [PATCH] x86: Call __va() to get trampoline_base.

On 12/04/2009 08:26 AM, Rakib Mullick wrote:
>  x86, tboot: Call __va() to get trampoline_base.
> 
>  Do not pass trampoline_base as parameter of virt_to_phys.
> Because trampoline_base is in .cpuinit.data section, but its
> called from non-cpuinit function. So use __va(TRAMPOLINE_BASE)
> instead of trampoline_base, which helps to fix section mismatch.
> 
> We were warned by the following warning:
> 
>   LD      arch/x86/kernel/built-in.o
> WARNING: arch/x86/kernel/built-in.o(.text+0x13c5f): Section mismatch
> in reference from the function tboot_setup_sleep() to the variable
> .cpuinit.data:trampoline_base
> The function tboot_setup_sleep() references
> the variable __cpuinitdata trampoline_base.
> This is often because tboot_setup_sleep lacks a __cpuinitdata
> annotation or the annotation of trampoline_base is wrong.
> 
> Signed-off-by: Rakib Mullick <rakib.mullick@...il.com>

This is a bug, but this isn't the right fix.

trampoline.c has:

#if defined(CONFIG_X86_64) && defined(CONFIG_ACPI_SLEEP)
#define __trampinit
#define __trampinitdata
#else
#define __trampinit __cpuinit
#define __trampinitdata __cpuinitdata
#endif

... because on i386 we don't use the trampoline for ACPI return.

This means one of these is true:

- Either we need the AP trampoline for tboot on i386, and the above
definition in trampoline.c needs to be fixed; or
- The CONFIG_X86_TRAMPOLINE in tboot.c is too generous, and in fact it
needs to be set to defined(CONFIG_X86_64) && defined(CONFIG_ACPI_SLEEP)
just like the above code.

Sending to Joseph and Shane to figure out...

	-hpa
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