Re: [Xen-devel] [PATCH for-next 9/9] xen: Remove mfn_to_gmfn macro

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 13.03.19 at 18:34, <andrew.cooper3@xxxxxxxxxx> wrote:
> On 13/03/2019 15:59, Jan Beulich wrote:
>>>>> On 13.03.19 at 16:48, <julien.grall@xxxxxxx> wrote:
>>> On 13/03/2019 15:40, Jan Beulich wrote:
>>>>>>> On 13.03.19 at 16:24, <julien.grall@xxxxxxx> wrote:
>>>>> On 13/03/2019 15:22, Jan Beulich wrote:
>>>>>>>>> On 18.02.19 at 12:36, <julien.grall@xxxxxxx> wrote:
>>>>>>> --- a/xen/include/asm-arm/mm.h
>>>>>>> +++ b/xen/include/asm-arm/mm.h
>>>>>>> @@ -321,10 +321,8 @@ struct page_info *get_page_from_gva(struct vcpu 
>>>>>>> *v, 
>>> vaddr_t va,
>>>>>>>    #define SHARED_M2P_ENTRY         (~0UL - 1UL)
>>>>>>>    #define SHARED_M2P(_e)           ((_e) == SHARED_M2P_ENTRY)
>>>>>>>    
>>>>>>> -/* Xen always owns P2M on ARM */
>>>>>>> +/* We don't have a M2P on Arm */
>>>>>>>    #define set_gpfn_from_mfn(mfn, pfn) do { (void) (mfn), (void)(pfn); 
>>>>>>> } 
>>> while (0)
>>>>>>> -#define mfn_to_gmfn(_d, mfn)  (mfn)
>>>>>> So is the plan to remove the other macro from Arm then as well?
>>>>> Do you mean mfn_to_gfn? If so it does not exist on Arm.
>>>> No, I mean the one in context above - set_gpfn_from_mfn().
>>> It is used in common code, so we would need to #idef the caller.
>> Hmm, right, such #ifdef-ary would be undesirable (and two out of
>> the three common code callers would need it.
>>
>>> I think it is better to provide a NOP implementation. Could be moved 
>>> somewhere 
>>> in the common header though. Any opinions?
>> This would perhaps be better, now that you have HAVE_M2P.
> 
> Given that "having an M2P" is now an x86-specific concept, I think
> phasing set_gpfn_from_mfn()'s use out of common code is the way to go.

But what's the implication of this? There would need to be some
arch_*() hook used in the place that set_gpfn_from_mfn() is
invoked currently. But then it can as well remain
set_gpfn_from_mfn() (with the !HAVE_M2P stubbed out properly
in a common header), can't it?

Jan



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