Re: [Xen-devel] [PATCH 1/9] x86/hypercall: Move some of the hvm hypercall infrastructure into hypercall.h

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 02.08.16 at 16:59, <andrew.cooper3@xxxxxxxxxx> wrote:
> On 02/08/16 15:54, Jan Beulich wrote:
>>>>> On 02.08.16 at 16:26, <julien.grall@xxxxxxx> wrote:
>>> On 02/08/16 15:17, Jan Beulich wrote:
>>>> Well, I find it quite odd for hypercall argument counts to differ
>>>> between arches. I.e. I'd conclude the ABI was mis-specified.
>>> Is it documented somewhere for the x86 code? Looking at Linux, the 
>>> privcmd call is only passing 5 arguments on both ARM and x86.
>> arch-x86/xen-x86_32.h has
>>
>>  * Hypercall interface:
>>  *  Input:  %ebx, %ecx, %edx, %esi, %edi, %ebp (arguments 1-6)
>>  *  Output: %eax
>>
>> while arch-x86/xen-x86_64.h has
>>
>>  * Hypercall interface:
>>  *  Input:  %rdi, %rsi, %rdx, %r10, %r8, %r9 (arguments 1-6)
>>  *  Output: %rax
> 
> The only actual 6 argument hypercall is the v4v hypercall, better known
> as __HYPERVISOR_xc_reserved_op at index 39, but that isn't implemented
> anywhere upstream.

But it serves as an example what now wouldn't work on ARM.

Jan


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