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Re: [Xen-devel] [PATCH 03/17] xen/mm: Move the MM types in a separate header

Hi Jan,

On 26/03/2020 09:02, Jan Beulich wrote:
On 25.03.2020 19:09, Julien Grall wrote:
Hi Jan,

On 25/03/2020 15:00, Jan Beulich wrote:
On 22.03.2020 17:14, julien@xxxxxxx wrote:
From: Julien Grall <jgrall@xxxxxxxxxx>

It is getting incredibly difficult to use typesafe GFN/MFN/PFN in the
headers because of circular dependency. For instance, asm-x86/page.h
cannot include xen/mm.h.

In order to convert more code to use typesafe, the types are now moved
in a separate header that requires only a few dependencies.

We definitely need to do this, so thanks for investing the
time. I think though that we want to settle up front (and
perhaps record in a comment in the new header) what is or
is not suitable to go into the new header. After all you're
moving not just type definitions, but also simple helper

I am expecting headers to use the typesafe helpers (such mfn_add)
in the long term. So I would like the new header to contain the
type definitions and any wrappers that would turn 'generic'
operations safe.

I am not entirely sure yet how to formalize the rules in the
header. Any ideas?

Well, if the header was just for the typesafe types, it could be
renamed (to e.g. mm-typesafe.h) and be left without any respective
comment. The issue I've mentioned arises if, with its currently
suggested name, further types get added. In such a case perhaps it
could be "type definitions and their immediate accessors,
involving no other non-trivial types"?

I will rename the file to mm-typesafe.h.


Julien Grall



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