Re: [Xen-devel] [PATCH v2] boot allocator: Use arch helper for virt_to_mfn on DIRECTMAP

[Julien Grall <julien.grall@xxxxxxx>]

Hi Vijay,

On 03/15/2017 05:11 AM, Vijay Kilari wrote:
> On Tue, Mar 14, 2017 at 9:02 PM, Julien Grall <julien.grall@xxxxxxx> wrote:
> > Hello Vijay,
> >
> > On 13/03/17 11:43, vijay.kilari@xxxxxxxxx wrote:
> > > From: Vijaya Kumar K <Vijaya.Kumar@xxxxxxxxxx>
> > >
> > > On ARM, virt_to_mfn uses the hardware for address
> > > translation. So if the virtual address is not mapped translation
> > > fault is raised.On ARM, DIRECTMAP_VIRT region is direct mapped.
> >
> > This is not true. As I said before, all the memory will be direct mapped on
> > ARM64 but not on ARM32.
> >
> > For ARM32, only xenheap will be direct mapped. So you may want to return
> > is_xenheap_mfn(...). Or even return false in all the case. Either is fine by
> > me, but it would need to be explained in the code.
> Is this ok?.
>
> /*
>  * On ARM64 DIRECTMAP_VIRT region is directly mapped. Hence return true;
>  * On ARM only xenheap memory is directly mapped. Hence return false.
>  */
> static inline bool_t arch_mfn_below_directmap_max_mfn(unsigned long mfn)
> {
> #ifdef CONFIG_ARM_64
>     return true;
> #else
>     return false;
> #endif
> }
I would implement the helper in {arm32,arm64}/mm.h and avoid the #ifdef 
in the implementation.
Cheers,

--
Julien Grall

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