Re: [PATCH 1/2] xen/arm: add support for vm_assist hypercall

[Juergen Gross <jgross@suse.com>]

On 20/05/16 16:51, Jan Beulich wrote:
>>>> On 20.05.16 at 16:42, <JGross@suse.com> wrote:
>> On 20/05/16 16:34, Jan Beulich wrote:
>>>>>> On 20.05.16 at 15:22, <JGross@suse.com> wrote:
>>>> --- a/xen/common/domain.c
>>>> +++ b/xen/common/domain.c
>>>> @@ -1408,7 +1408,6 @@ long do_vcpu_op(int cmd, unsigned int vcpuid, 
>> XEN_GUEST_HANDLE_PARAM(void) arg)
>>>>      return rc;
>>>>  }
>>>>  
>>>> -#ifdef VM_ASSIST_VALID
>>>>  long vm_assist(struct domain *p, unsigned int cmd, unsigned int type,
>>>>                 unsigned long valid)
>>>>  {
>>>> @@ -1427,7 +1426,6 @@ long vm_assist(struct domain *p, unsigned int cmd, 
>>>> unsigned int type,
>>>>  
>>>>      return -ENOSYS;
>>>>  }
>>>> -#endif
>>>>  
>>>>  struct pirq *pirq_get_info(struct domain *d, int pirq)
>>>>  {
>>>> --- a/xen/common/kernel.c
>>>> +++ b/xen/common/kernel.c
>>>> @@ -441,12 +441,10 @@ DO(nmi_op)(unsigned int cmd, 
>> XEN_GUEST_HANDLE_PARAM(void) arg)
>>>>      return rc;
>>>>  }
>>>>  
>>>> -#ifdef VM_ASSIST_VALID
>>>>  DO(vm_assist)(unsigned int cmd, unsigned int type)
>>>>  {
>>>>      return vm_assist(current->domain, cmd, type, VM_ASSIST_VALID);
>>>>  }
>>>> -#endif
>>>
>>> Removing these #ifdef-s is neither necessary for this patch (at least
>>> afaict) nor desirable (after all they had got added so that an arch
>>> doesn't get this code compiled for no reason).
>>
>> Removing is not necessary, right.
>>
>> OTOH there is no arch left needing those #ifdef-s to be in place. Or do
>> you think we should guard each single functionality in xen/common by
>> such means? I don't think so. In this case keeping the #ifdef-s would be
>> for historical reasons only.
> 
> No, I don't want to go overboard with this. But we added these
> not so long ago, so I see no reason why they should now be
> removed again, just to maybe have them added in a couple of
> years again.

Hmm, those #ifdef-s where needed for ARM, as on ARM there just was no
flag to be set via vm_assist hypercall. The new flag added in the next
patch is suitable for all architectures, so there would be no reason
for not supporting vm_assist in a new to be supported architecture.


Juergen


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