Message-ID: <442110F0.9090805@vmware.com>
Date: Wed, 22 Mar 2006 00:55:12 -0800
From: Zachary Amsden <zach@vmware.com>
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To: Chris Wright <chrisw@sous-sol.org>
Cc: linux-kernel@vger.kernel.org, xen-devel@lists.xensource.com,
       virtualization@lists.osdl.org, Ian Pratt <ian.pratt@xensource.com>,
       Christian Limpach <Christian.Limpach@cl.cam.ac.uk>
Subject: Re: [RFC PATCH 19/35] subarch support for control register accesses
References: <20060322063040.960068000@sorel.sous-sol.org> <20060322063754.391952000@sorel.sous-sol.org>
In-Reply-To: <20060322063754.391952000@sorel.sous-sol.org>
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Chris Wright wrote:
> +#define read_cr4_safe() ({			      \
> +	unsigned int __dummy;			      \
> +	/* This could fault if %cr4 does not exist */ \
> +	__asm__("1: movl %%cr4, %0		\n"   \
> +		"2:				\n"   \
> +		".section __ex_table,\"a\"	\n"   \
> +		".long 1b,2b			\n"   \
> +		".previous			\n"   \
> +		: "=r" (__dummy): "0" (0));	      \
> +	__dummy;				      \
> +})

I think you'll find trap and emulate quite sufficient for this one.

> +#define stts() write_cr0(8 | read_cr0())
>   

Nit: You shouldn't need to redefine stts() in the subarch.
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