Re: [PATCH 1/4] [HYPERCALL] Add hypercalls functions

[Anthony Liguori <anthony-rdkfGonbjUSkNkDKm+mE6A@public.gmane.org>]

On Fri, 2007-08-24 at 16:57 -0700, Dor Laor wrote:
> The hypercalls can be called with various parameters number.
> Both x86_64 and i386 are supported.
> 
> Signed-off-by: Dor Laor <dor.laor-atKUWr5tajBWk0Htik3J/w@public.gmane.org>
> ---
> +static inline int
> +__hypercall6(unsigned int nr, unsigned long p1, unsigned long p2,
> +	     unsigned long p3, unsigned long p4, unsigned long p5,
> +	     unsigned long p6)
> +{
> +	int ret;
> +	asm (" call hypercall_addr\n"
> +		: "=a" (ret)
> +		: "b" (nr),
> +		  "a" (p1),
> +		  "c" (p2),
> +		  "d" (p3),
> +		  "S" (p4),
> +		  "D" (p5),
> +		  "bp" (p6)
> +		: "memory", "cc"
> +	);
> +	return ret;
> +}
> +
> +#define hypercall(nr_params, args...)			\
> +({							\
> +	/* __ret is volatile to make sure call to this	\
> +	 * function isn't optimized away by gcc. Just	\
> +	 * having the __hypercallN() functions mention	\
> +	 * memory is clobbered isn't enough		\
> +	 */						\
> +	volatile int __ret;				\
> +							\
> +	__ret = __hypercall##nr_params(args);		\
> +							\
> +	__ret;						\
> +})

A couple things are different in my patchset.  I didn't do this
hypercall macro.  I tried it at first but IMHO it was pretty ugly.  It
makes things less readable to me.  The second thing is I only have up to
4 parameters to a hypercall.  That leaves some GP registers on 32-bit
and Xen seems to be happily using 4 registers so I don't think there's
anything we can't express without the extra 2.

Regards,

Anthony Liguori


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