Re: [Xen-devel] Re: [Xen-changelog] Linux scrubs memory before returnign it to Xen, or transferring it to

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

> > +#ifdef CONFIG_XEN_SCRUB_PAGES
> > +        else
> > +        {
> > +            void *p = kmap(&mem_map[*currp]);
> > +            scrub_pages(p, 1);
> > +            kunmap(&mem_map[*currp]);
> > +        }
> > +#endif
> 
> Since scrub_pages() becomes a NOOP when the config option
> is not set, why the additional #ifdef in the source code ?

Avoids an unnecessary kmap/kunmap, which in Xen would both trap to
ring 0. I don't know if it would make much of a performance
difference, but I decided to ifdef the whole thing just in case.

I hope you like the abuse of __dev_alloc_skb() :-)

 -- Keir


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