linux-kernel - Re: [RFC PATCH 16/33] Add support for Xen to entry.S.

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Message-Id: <1153217516.3038.34.camel@laptopd505.fenrus.org>
Date:	Tue, 18 Jul 2006 12:11:56 +0200
From:	Arjan van de Ven <arjan@...radead.org>
To:	Chris Wright <chrisw@...s-sol.org>
Cc:	linux-kernel@...r.kernel.org, virtualization@...ts.osdl.org,
	xen-devel@...ts.xensource.com,
	Jeremy Fitzhardinge <jeremy@...p.org>, Andi Kleen <ak@...e.de>,
	Andrew Morton <akpm@...l.org>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Zachary Amsden <zach@...are.com>,
	Ian Pratt <ian.pratt@...source.com>,
	Christian Limpach <Christian.Limpach@...cam.ac.uk>,
	Jeremy Fitzhardinge <jeremy@...source.com>
Subject: Re: [RFC PATCH 16/33] Add support for Xen to entry.S.

On Tue, 2006-07-18 at 00:00 -0700, Chris Wright wrote:
> +#ifndef CONFIG_XEN
>  	movl %cr0, %eax
>  	testl $0x4, %eax		# EM (math emulation bit)
> -	jne device_not_available_emulate
> -	preempt_stop
> -	call math_state_restore
> -	jmp ret_from_exception
> -device_not_available_emulate:
> +	je device_available_emulate
>  	pushl $0			# temporary storage for ORIG_EIP
>  	CFI_ADJUST_CFA_OFFSET 4
>  	call math_emulate
>  	addl $4, %esp
>  	CFI_ADJUST_CFA_OFFSET -4
> +	jmp ret_from_exception
> +device_available_emulate:
> +#endif


Hi,

can you explain what this chunk is for? It appears to be for the non-xen
case due to the ifndef, yet it seems to visibly change the code for
that... that deserves an explanation for sure ...

Greetings,
   Arjan van de Ven

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