Re: [Xen-devel] [PATCH 00/16] x86: indirect call overhead reduction

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 13.07.18 at 19:15, <julien.grall@xxxxxxx> wrote:
> On 13/07/18 15:27, Jan Beulich wrote:
>>>>> On 13.07.18 at 15:39, <julien.grall@xxxxxxx> wrote:
>>> On 13/07/18 14:27, Jan Beulich wrote:
>>>>>>> On 13.07.18 at 15:00, <julien.grall@xxxxxxx> wrote:
>>>>> What would be the generic interface here? I saw it was based on
>>>>> alternative for the plumbing.
>>>>
>>>> Yes, I'd prefer to use the same mechanism as presented in the series.
>>>> As per above for the IOMMU case we'd then need another abstraction
>>>> layer put in the middle (to produce a patch site on x86, but a normal
>>>> [indirect] call on ARM).
>>>
>>> I will have a look. Could you point to the patch adding the abstraction?
>> 
>> Patch 9 is where the x86 side infrastructure gets added. Typical uses
>> would then be (taken from patch 10)
>> 
>>   hvm_guest_x86_mode(struct vcpu *v)
>>   {
>>       ASSERT(v == current);
>> -    return hvm_funcs.guest_x86_mode(v);
>> +    return alternative_call1(hvm_funcs.guest_x86_mode, v);
> OOI, is there any reason for you to define alternative_callN and not 
> providing a generic version (similar to arm_smccc_1_1_smc in 
> include/asm-arm/smccc.h)?

Oh, that's a nice approach - I'll try to switch to that.

Jan



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