Messages in this thread | | | Subject | Re: Access to non-RAM pages | From | Benjamin Herrenschmidt <> | Date | Mon, 03 Sep 2018 11:44:20 +1000 |
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On Sun, 2018-09-02 at 18:38 -0700, Linus Torvalds wrote: > On Sun, Sep 2, 2018 at 6:32 PM Benjamin Herrenschmidt > <benh@kernel.crashing.org> wrote: > > > > Also, if we cross page boundaries with those guys then we have a bigger > > problem no ? we could fall off a vmalloc page into the nether or into > > an ioremap mapping no ? > > It's not used for vmalloc stuff. It's just regular kmalloc(). > > So it can cross pages, and it can fall off the end of memory, but it > can't do random stuff.
Ok, it might be worth adding a DEBUG_VM based (or similar) warning in case somebody ever thinks of passing a vmalloc pointer to it...
As for falling out of the end of memory, yes it could be a real problem though I don't see why IO is any different than just hitting a non- mapped area in that regard. So we should probably keep an unused (readonly if possible) zero page at the end.
Cheers, Ben.
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