Re: [Xen-devel] [PATCH] x86/numa: Adjust datatypes for node and pxm

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

On 02/23/2015 04:57 AM, Jan Beulich wrote:
> > > > On 21.02.15 at 19:14, <boris.ostrovsky@xxxxxxxxxx> wrote:
> > Use u8-sized node IDs and unsigned PXMs consistently throughout
> > code (and introduce nodeid_t type).
> >
> > Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
> I think the description should call out areas not covered, like the
> node encoding in the top bits of MEMF_*.
>
> > --- a/xen/arch/x86/srat.c
> > +++ b/xen/arch/x86/srat.c
> > @@ -21,44 +21,55 @@
> >   #include <asm/e820.h>
> >   #include <asm/page.h>
> >   
> > +#define MAX_PXM   255
> Perhaps better (MAX_NUMNODES - 1) than a literal number? Or
> even do away with it altogether, use MAX_NUMNODES - 1 in the
> array definition and ARRAY_SIZE() elsewhere?
I am not sure we can do this: PXMs are not guaranteed to be zero-based.

And, in fact, the way we map PXMs to nodes is not quite right because of 
this --- it just so happens that PXMs are usually under 255 (and 
zero-based) and we can use them as index to 255-sized array. IIRC the 
spec defines them as 32-bit values.
-boris

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