Xen devel - Apr 2006 - RE: Hypercall number assignment convension (was Re: Re:[PATCH]: kexec: framework and i386)

>From: Isaku Yamahata
>Sent: 2006年4月26日 10:10
>
>On Mon, Apr 24, 2006 at 08:32:09AM +0100, Keir Fraser wrote:
>
>> The list of __HYPERVISOR_* defines in public/xen.h in the main xen
>> repository is the canonical place. For hypercalls in our tree, simply
>> grabbing the next number in sequence usually makes sense. I''m
not
>sure
>> whether having structure to the hypercall numbers makes sense (e.g.,
>a
>> range for arch-specific usage) -- if so then maybe allocating from 64
>> upwards would make sense.
>
>Actually xen/ia64 requires only one hypercall number for now.
>I attached the patches to take one.
>I''m not sure what name you prefer, so I attached two patches.
>Please apply which you prefer. (or invent whatever name you like.)
>
>--
I prefer to the first one. However not the current 
__HYPERVISOR_arch_specific_0, *_1, *_2, ..., how about just call 
it as __HYPERVISOR_arch_specific_ops which contains another 
namespace defined by different architecture seperately?

Thanks,
Kevin

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On 26 Apr 2006, at 03:34, Tian, Kevin wrote:
> I prefer to the first one. However not the current
> __HYPERVISOR_arch_specific_0, *_1, *_2, ..., how about just call
> it as __HYPERVISOR_arch_specific_ops which contains another
> namespace defined by different architecture seperately?
Sometimes you might want a fast hypercall that doesn''t have two levels 
of demultiplexing, or where the register/stack parameters are carefully 
crafted and would not fit with an ioctl()-style hypercall (see x86''s 
IRET hypercall).

How about reserving 8 or 16 arch-specific hypercalls up front?
#define __HYPERVISOR_arch_0  32
  ...
#define __HYPERVISOR_arch_7  39

We could give a bit of breathing space to the non-arch range by 
starting __HYPERVISOR_arch_* at. e.g., 40 or 48?

  -- Keir


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