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RE: Hypercall number assignment convension (was Re: [Xen-devel] Re:[PATC

To: "Keir Fraser" <Keir.Fraser@xxxxxxxxxxxx>
Subject: RE: Hypercall number assignment convension (was Re: [Xen-devel] Re:[PATCH]: kexec: framework and i386)
From: "Tian, Kevin" <kevin.tian@xxxxxxxxx>
Date: Wed, 26 Apr 2006 15:54:05 +0800
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx, Akio Takebe <takebe_akio@xxxxxxxxxxxxxx>, Isaku Yamahata <yamahata@xxxxxxxxxxxxx>, Magnus Damm <magnus@xxxxxxxxxxxxx>, Horms <horms@xxxxxxxxxxxx>, Mark Williamson <mark.williamson@xxxxxxxxxxxx>
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Thread-topic: Hypercall number assignment convension (was Re: [Xen-devel] Re:[PATCH]: kexec: framework and i386)
>From: Keir Fraser [mailto:Keir.Fraser@xxxxxxxxxxxx]
>Sent: 2006年4月26日 15:38
>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

Then we may need to fill that breathing space with do_ni_hypercall 
to ensure no leakage from NR_hypercall check. If that's the case, 
how about define the __HYPERVISOR_arch_* at end of 256 spaces, 
and fill all unused entries with do_ni_hypercall. By that way, the check
to illegal hypercall (<256) is a bit slower, however it shouldn't matter 
for that rare cases.


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