On 28/07/15 16:02, Julien Grall wrote:

Based on include/xen/mm.h [1], Linux is mistakenly using MFN when GFN
is meant, I suspect this is because the first support for Xen was for
PV. This brough some misimplementation of helpers on ARM and make the
developper confused the expected behavior.

For the benefit of other subsystem maintainers, this is a purely
mechanical change in Xen-specific terminology.  It doesn't need reviews
or acks from non-Xen people (IMO).

For instance, with pfn_to_mfn, we expect to get an MFN based on the name.
Although, if we look at the implementation on x86, it's returning a GFN.

For clarity and avoid new confusion, replace any reference of mfn into
gnf in any helpers used by PV drivers.

Take also the opportunity to simplify simple construction such
as pfn_to_mfn(page_to_pfn(page)) into page_to_gfn. More complex clean up
will come in follow-up patches.

I think it may be possible to do further clean up in the x86 code to
ensure that helpers returning machine address (such as virt_address) is
not used by no auto-translated guests. I will let x86 xen expert doing
it.

Reviewed-by: David Vrabel <redacted>

It looks a bit odd to use GFN in some of the PV code where the
hypervisor API uses MFN but overall I think using the correct
terminology where possible is best.  But I'd like to have Boris's or
Konrad's opinion on this.

David