XENMAPSPACE_grant_table vs. GNTTABOP_setup_table

[Martin Lucina <martin@xxxxxxxxxx>]

Hi,

I've been making progress on bootstrapping a new, PVHv2 only, Xen platform
stack for MirageOS [1]. The basics are now functional and I have started to
re-implement the grant table code.

After studying both the Mini-OS and Linux implementations some, I don't
understand the difference between using XENMAPSPACE_grant_table vs.
GNTTABOP_setup_table to set up the initial grant table mapping for the
guest.

Are these calls just newer and older ways of accomplishing the same thing?
The Linux driver seems to use both in various conditions, whereas Mini-OS
uses the former on ARM and the latter on x86.

If these are functionally equivalent, then for my purposes I'd rather use
XENMAPSPACE_setup_table, since IIUC this lets me map the grant table at an
address of my choosing rather than GNTTABOP_setup_table which at least on
x86_64 appears to be returning PFNs at the top of the address space.

Any advice much appreciated,

-mato

[1] https://github.com/mirage/mirage/issues/1159