On Tue, 2015-02-24 at 09:09 +0100, Ingo Molnar wrote: > * Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: > > > <reads the code> > > > > Oh. We don't do any checking at all. We're just telling > > userspace programmers "don't do that". hrm. What are > > your thoughts on adding the overlap checks to the kernel? > > I have requested such sanity checking in previous review as > well, it has to be made fool-proof for this optimization to > be usable. > > Another alternative would be to make this not a transparent > optimization, but a separate API: ioremap_hugepage() or so. > > The devices and drivers dealing with GBs of remapped pages > is still relatively low, so they could make explicit use of > the API and opt in to it. > > What I was arguing against was to make it a CONFIG_ option: > that achieves very little in practice, such APIs should be > uniformly available. I was able to come up with simple changes that fall back to 4KB mappings when a target range is covered by MTRRs. So, with the changes, it is now safe to enable huge page mappings to ioremap() transparently without such restriction. I will post updated patchset hopefully soon. Thanks, -Toshi -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>