Re: [Xen-devel] [PATCH v8 04/15] xen: add function for obtaining highest possible memory address

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 20.09.17 at 10:58, <jgross@xxxxxxxx> wrote:
> On 20/09/17 10:57, Jan Beulich wrote:
>>>>> On 20.09.17 at 08:34, <jgross@xxxxxxxx> wrote:
>>> --- a/xen/arch/x86/mm.c
>>> +++ b/xen/arch/x86/mm.c
>>> @@ -6312,6 +6312,17 @@ int pv_ro_page_fault(unsigned long addr, struct 
> cpu_user_regs *regs)
>>>      return 0;
>>>  }
>>>  
>>> +unsigned long arch_get_upper_mfn_bound(void)
>>> +{
>>> +    unsigned long max_mfn;
>>> +
>>> +    max_mfn = mem_hotplug ? PFN_DOWN(mem_hotplug) : max_page;
>> 
>> Taking into account the code in the caller of this function as well
>> as the ARM counterpart I find the use of max_page here odd. I'd
>> prefer if get_upper_mfn_bound() went away altogether, and it's
>> sole caller (which strangely enough doesn't get introduced here)
>> called the arch function directly. Additionally, with the caller being
>> a sysctl, how is that supposed to help a PV DomU kernel in their
>> choice of grant table version?
> 
> Did you look at patch 15?

Not yet, no (I had looked over the titles, but this one's didn't
make me make the connection). So yes, that addresses the PV
DomU concern. Still I'd like to get away without the thin common
wrapper around the arch specific actual implementation (and I
don't care much whether the resulting function has an arch_
prefix).

Jan


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