Re: [Xen-devel] [PATCH v6 02/23] xen: move NUMA_NO_NODE to public memory.h as XEN_NUMA_NO_NODE

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Mon, Mar 02, 2015 at 04:27:25PM +0000, Jan Beulich wrote:
> >>> On 02.03.15 at 17:08, <wei.liu2@xxxxxxxxxx> wrote:
> > On Mon, Mar 02, 2015 at 03:51:37PM +0000, Jan Beulich wrote:
> >> >>> On 02.03.15 at 16:38, <wei.liu2@xxxxxxxxxx> wrote:
> >> > On Mon, Mar 02, 2015 at 03:30:21PM +0000, Ian Campbell wrote:
> >> >> On Mon, 2015-03-02 at 07:04 +0000, Jan Beulich wrote:
> >> >> > >>> Andrew Cooper <andrew.cooper3@xxxxxxxxxx> 02/27/15 5:58 PM >>>
> >> >> > >On 27/02/15 16:51, Wei Liu wrote:
> >> >> > >> During last round review, Andrew wanted me to move this to Xen 
> >> >> > >> public
> >> >> > >> header to avoid reinventing it in libxc. Now this value is used in 
> >> >> > >> libxc
> >> >> > >> patch.
> >> >> > >>
> >> >> > >> But I don't particularly mind whether we move it or not, it's up 
> >> >> > >> to you
> >> >> > >> maintainers to decide.
> >> >> > >
> >> >> > >It is a sentinel value used in the public ABI.  It should therefore
> >> >> > >appear in the public API.
> >> >> > 
> >> >> > Which it already does, as XENMEMF_get_node(0). I don't think it needs
> >> >> > particular naming as a new constant, even more that it isn't intended 
> >> >> > to
> >> >> > be used explicitly in any of the memops.
> >> >> 
> >> >> IMHO the named constant does seem to make the tools code at least more
> >> >> readable, but without Wei having said where this is to be used I'm not
> >> >> sure where it should live. In particular I'm unsure if/how/where this
> >> >> value gets passed to a hypercall, as opposed to perhaps being used as a
> >> > 
> >> > This is used to fill in vnode_to_pnode array. That array get
> >> > subsequently passed down to hypervisor.
> >> 
> >> Do we really accept NUMA_NO_NODE to be passed that way?
> >> 
> > 
> > public/domctl.h:struct xen_domctl_vnuma has vnode_to_pnode array.
> 
> That wasn't my concern - I was rather wondering why we would
> accept any of this array's fields to be set to "no node".
> 

If you want to have numa topology exposed to guest but doesn't care
about underly memory affinity?

My code as is doesn't support this kind of setting though.

Wei.


> Jan

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