linux-kernel - Re: [PATCH v9 06/12] x86-64, hotplug: Add start_cpu0() entry point to head

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Date:	Tue, 16 Oct 2012 18:50:07 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Fenghua Yu <fenghua.yu@...el.com>
Cc:	Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>,
	H Peter Anvin <hpa@...or.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Asit K Mallick <asit.k.mallick@...el.com>,
	Tony Luck <tony.luck@...el.com>,
	Arjan Dan De Ven <arjan@...ux.intel.com>,
	Suresh B Siddha <suresh.b.siddha@...el.com>,
	Len Brown <len.brown@...el.com>,
	"Srivatssa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>,
	Randy Dunlap <rdunlap@...otime.net>,
	Chen Gong <gong.chen@...ux.intel.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	linux-pm <linux-pm@...r.kernel.org>, x86 <x86@...nel.org>
Subject: Re: [PATCH v9 06/12] x86-64, hotplug: Add start_cpu0() entry point
 to head_64.S

On Fri, Oct 12, 2012 at 09:09:43AM -0700, Fenghua Yu wrote:
> From: Fenghua Yu <fenghua.yu@...el.com>
> 
> start_cpu0() is defined in head_64.S for 64-bit. The function sets up stack and
> jumps to start_secondary() for CPU0 wake up.
> 
> Signed-off-by: Fenghua Yu <fenghua.yu@...el.com>
> ---
>  arch/x86/kernel/head_64.S |   15 +++++++++++++++
>  1 files changed, 15 insertions(+), 0 deletions(-)
> 
> diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
> index 94bf9cc..3faac8a 100644
> --- a/arch/x86/kernel/head_64.S
> +++ b/arch/x86/kernel/head_64.S
> @@ -252,6 +252,21 @@ ENTRY(secondary_startup_64)
>  	pushq	%rax		# target address in negative space
>  	lretq
>  
> +#ifdef CONFIG_HOTPLUG_CPU
> +/*
> + * Boot CPU0 entry point. It's called from play_dead(). Everything has been set
> + * up already except stack. We just set up stack here. Then call
> + * start_secondary().
> + */
> +ENTRY(start_cpu0)
> +	movq stack_start(%rip),%rsp
> +	movq	initial_code(%rip),%rax
> +	pushq	$0		# fake return address to stop unwinder
> +	pushq	$__KERNEL_CS	# set correct cs
> +	pushq	%rax		# target address in negative space
> +	lretq

ENDPROC(start_cpu0) maybe?

Ditto for head_32.S in the next patch.

Thanks.

-- 
Regards/Gruss,
Boris.
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