Re: [Xen-devel] [PATCH v2] xen/x86: add a way to obtain the needed number of memory map entries

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Tue, Dec 06, 2016 at 07:19:13AM -0700, Jan Beulich wrote:
> >>> On 06.12.16 at 14:47, <JGross@xxxxxxxx> wrote:
> > Today there is no way for a domain to obtain the number of entries of
> > the machine memory map returned by XENMEM_machine_memory_map hypercall.
> > 
> > Modify the interface to return just the needed number of map entries
> > in case the buffer was specified as NULL.
> > 
> > Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
> 
> Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
> 
> albeit I'd like to have at least one more REST maintainer's agreement
> that ...
> 
> > --- a/xen/include/public/memory.h
> > +++ b/xen/include/public/memory.h
> > @@ -339,6 +339,8 @@ DEFINE_XEN_GUEST_HANDLE(xen_memory_map_t);
> >  /*
> >   * Returns the real physical memory map. Passes the same structure as
> >   * XENMEM_memory_map.
> > + * Specifying buffer as NULL will return the number of entries required
> > + * to store the complete memory map.
> >   * arg == addr of xen_memory_map_t.
> >   */
> >  #define XENMEM_machine_memory_map   10
> 
> ... this slight behavioral change is fine to make.

I think it is fine. It won't break the existing guests. And it is inline
with what we are doing when retroffiting other hypercalls.

Thanks.

> 
> Jan
> 

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel