Re: [Xen-devel] [PATCH v13 3/3] iommu: add rmrr Xen command line option for extra rmrrs

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 18.01.17 at 20:56, <elena.ufimtseva@xxxxxxxxxx> wrote:
> I am looking at rmrr_identity_mapping where the RMRR paddr get converted
> to pfn and then mapped with iommu.
> If ( rmrr->end_address & ~PAGE_SHIFT_MASK_4K ) == 0, the while loop
>     while ( base_pfn < end_pfn )
>  will not map that inclusive end_address of rmrr.
> Does it seem wrong?

I don't think so, no. end_pfn is being calculated using
PAGE_ALIGN_4K(), i.e. rounding up.

>> > +        rmrr->segment = seg;
>> > +        rmrr->base_address = pfn_to_paddr(user_rmrrs[i].base_pfn);
>> > +        rmrr->end_address = pfn_to_paddr(user_rmrrs[i].end_pfn + 1);
>> 
>> "And this seems wrong too, unless I'm mistaken with the inclusive-ness."
>> 
> This one is the avoidance of the while loop mapping in
> rmrr_identity_mapping.

Well, that's the purpose you describe, but the comment was about
the calculation itself, which I think is lacking a "- 1", but even better
would be - for avoiding boundary issues -

        rmrr->end_address = pfn_to_paddr(user_rmrrs[i].end_pfn) | ~PAGE_MASK;

or some such.

Jan


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