ccio-dma q about io pdir: is there a kernel mem space never paged?

Hello all,

Re-reading: <http://www.hpl.hp.com/hpjournal/96feb/feb96a6.pdf>

I noticed another detail:
sic "Recall that the I/O page directory contains all active address translations and must be memory-resident."

Those key words "must be memory-resident" would mean to me never paged (in/out)?

Even thought I read ./include/linux/gfp.h, it's not clear to me which could be the gfp_mask I can use in:

	ioc->pdir_base = (u64 *)__get_free_pages(GFP_KERNEL,
                                                 get_order(ioc->pdir_size));

to advise kernel to never paging this I/O page directory?

Any idea?

Tia,

	J.

The kernel is never paged out. Just think, if you page out the swapper, how could you page anything back in?