Re: [Xen-devel] [PATCH 11/14] xen/x86: mm: Re-implement set_gpfn_from_mfn() as a static inline function

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 10.05.19 at 15:41, <julien.grall@xxxxxxx> wrote:
> On 10/05/2019 14:35, Jan Beulich wrote:
>>>>> On 10.05.19 at 15:27, <julien.grall@xxxxxxx> wrote:
>>> On 10/05/2019 13:43, Jan Beulich wrote:
>>>>>>> On 07.05.19 at 17:14, <julien.grall@xxxxxxx> wrote:
>>>>> +static inline void set_gpfn_from_mfn(unsigned long mfn, unsigned long 
>>>>> pfn)
>>>>> +{
>>>>> +    struct domain *d = page_get_owner(mfn_to_page(_mfn(mfn)));
>>>>> +    unsigned long entry = (d && (d == dom_cow)) ? SHARED_M2P_ENTRY : pfn;
>>>>
>>>> The && here looks, ehm, funny, but I guess it's needed for early boot?
>>>
>>> I have no idea, this is x86 not Arm...
>>>
>>>> But that's perhaps a separate thing to clean up. However, looking at
>>>> this - why is Arm setting up dom_cow in the first place?
>>>
>>> Common code is using dom_cow, so I don't think we want it to be NULL on Arm 
>>> to
>>> avoid weird issues.
>> 
>> I didn't mean it to remain NULL. Common code doesn't dereference it
>> (and isn't supposed to), so I'd consider initializing it to some known
>> faulting non-NULL address, if there is such on Arm.
> 
> Patches are welcomed ;).

So is there such an address on Arm?

Jan



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