Re: [Xen-devel] [PATCH 3/4 RFC] x86/p2m: use large pages for MMIO mappings

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 29.09.15 at 13:33, <julien.grall@xxxxxxxxxx> wrote:
> On 15/09/15 08:34, Jan Beulich wrote:
>> RFC reasons:
>> - ARM side unimplemented (and hence libxc for now made cope with both
>>   models), the main issue (besides my inability to test any change
>>   there) being the many internal uses of map_mmio_regions())
> 
> map_mmio_regions is used in ARM to map all the device memory in a guest.
> We expect this function to map everything at once when called during
> DOM0 build and/or when a guest is created (used to map the interrupt
> controller).
> 
> I would rather prefer to avoid introducing specific helpers with
> slightly different behavior (i.e one is only mapping N page, the other
> everything).
> 
> What about extending map_mmio_regions to take a parameter telling if we
> want to limit the number of mapping in a single invocation?

Sure an option, albeit something that would be sufficient to be
done in ARM specific code, albeit the only user using variable
length is map_range_to_domain(). All the others, using fixed
lengths up to 32 pages, would implicitly get everything done at
once as long as the threshold is >= 32.

Jan


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