Re: [PATCH 06/10] xen: replace order with nr_pfns in assign_pages for better compatibility

[Julien Grall <julien@xxxxxxx>]

Hi Penny,

On 18/05/2021 06:21, Penny Zheng wrote:
> Function parameter order in assign_pages is always used as 1ul << order,
> referring to 2@order pages.
>
> Now, for better compatibility with new static memory, order shall
> be replaced with nr_pfns pointing to page count with no constraint,
> like 250MB.
We have similar requirements for LiveUpdate because are preserving the 
memory with a number of pages (rather than a power-of-two). With the 
current interface would be need to split the range in a power of 2 which 
is a bit of pain.
However, I think I would prefer if we introduce a new interface (maybe 
assign_pages_nr()) rather than change the meaning of the field. This is 
for two reasons:
  1) We limit the risk to make mistake when backporting a patch touch 
assign_pages().
  2) Adding (1UL << order) for pretty much all the caller is not nice.

Cheers,

--
Julien Grall