Re: [Xen-devel] [PATCH v2 1/4] pci: Do not ignore device's PXM information

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

On 01/07/2015 10:07 AM, Jan Beulich wrote:
> > > > On 07.01.15 at 15:47, <andrew.cooper3@xxxxxxxxxx> wrote:
> > On 07/01/15 14:42, Boris Ostrovsky wrote:
> > > I kept this field as an int to be able to store NUMA_NO_NODE which I
> > > thought to be (int)-1.
> > >
> > > But now I see that NUMA_NO_NODE is, in fact, 0xff but is promoted to
> > > (int)-1 by pxm_to_node(). Given that there is a number of tests for
> > > NUMA_NO_NODE and not for (int)-1, should we then make pxm_to_node()
> > > return u8 as well?
> > I noticed this as well, and found it quite counter intuitive.
> >
> > I would suggest fixing NUMA_NO_NODE to -1 and removing some of the
> > type-punning.
> I have to admit that I see no value in wasting 4 bytes for something
> that for the foreseeable future won't exceed 1 byte.
The downside of going to u8 is that we'd be limiting number of nodes to 
254, which is somewhat awkward. OTOH we already do this by testing 
nodeID against 0xff in various places.
-boris

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