Re: [PATCH V6 1/2] xen/arm: Introduce gpaddr_bits field to struct xen_domctl_getdomaininfo

[Ian Jackson <iwj@xxxxxxxxxxxxxx>]

Oleksandr Tyshchenko writes ("[PATCH V6 1/2] xen/arm: Introduce gpaddr_bits 
field to struct xen_domctl_getdomaininfo"):
> From: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
> 
> We need to pass info about maximum supported guest physical
> address space size to the toolstack on Arm in order to properly
> calculate the base and size of the extended region (safe range)
> for the guest. The extended region is unused address space which
> could be safely used by domain for foreign/grant mappings on Arm.
> The extended region itself will be handled by the subsequent
> patch.

You say "to the toolstack", but you are exposing this information up
to callers of libxl.  Do you mean some higher-layer toolstack that
uses libxl ?  What does it use this information for ?

FTAOD I am not opposed to exposing this in this way; indeed it seems
likely to be useful.  I just want to fully understand before I give
this my tools ack.

> +        info->gpaddr_bits = domctl.u.getdomaininfo.gpaddr_bits;

I'm pleased to find that this is not arch-specific.

Thanks,
Ian.