[Lguest] [patch][v2] cleanup hypercall code

[Jes Sorensen]

Rusty Russell wrote:
> On Mon, 2007-08-20 at 13:33 +0200, Jes Sorensen wrote:
>> Hi,
>>
>> Here's an updated version of the hypercall cleanup patch. I changed it
>> so the hcall_args are a union in struct lguest_regs on i386 - also
>> changed the e[a-d]x regs to be unsigned long as I presume they will be
>> 64 bit on x86_64 - trying to reduce the breakage there.
> 
> Some of this patch was missing (the union change).  I stuck with a cast
> for the moment, see below.

Argh, I must have forgotten to add that to my quilt files :( I've
attached it here.

>> The LG_GET_HCALL_ARGS I have kept as a macro. I tried turning it into
>> an inline, but that releases a whole avalanche of circular dependencies,
>> which I don't think is worth the hassle to get into.
> 
> Yeah, I lower-cased it since it has no side-effects.

Please don't do that!! The Linux convention is that macros are upper
case and functions are lower case names, as long as it's a macro it
should stay upper case.

> I'm now wondering if anyone is going to do something other than pass
> args in registers?  If not, we can do something like this in struct
> lguest:
> 
> 	/* The arguments for a hypercall are in registers. */
> 	union {
> 		struct hcall_args *hargs;
> 		struct lguest_regs *regs;
> 	};
> 
> An arch defines hcall_args and lguest_regs, so it can arrange them any
> way it wants...

Hmmm I don't think we want to rely on archs mapping things between the
two so I think it's better to do it on an arch level. In some cases
the arch may require to create a full args struct and pass it in to the
hypercall.

Cheers,
Jes
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