Messages in this thread | | | Date | Fri, 08 Feb 2013 12:50:15 -0800 | From | "H. Peter Anvin" <> | Subject | Re: [PATCH 1/2] add helper for highmem checks |
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On 02/08/2013 12:28 PM, Dave Hansen wrote: > #endif > diff -puN include/linux/mm.h~clean-up-highmem-checks include/linux/mm.h > --- linux-2.6.git/include/linux/mm.h~clean-up-highmem-checks 2013-02-08 08:42:37.295222148 -0800 > +++ linux-2.6.git-dave/include/linux/mm.h 2013-02-08 09:01:49.758254468 -0800 > @@ -1771,5 +1771,18 @@ static inline unsigned int debug_guardpa > static inline bool page_is_guard(struct page *page) { return false; } > #endif /* CONFIG_DEBUG_PAGEALLOC */ > > +static inline phys_addr_t last_lowmem_phys_addr(void) > +{ > + /* > + * 'high_memory' is not a pointer that can be dereferenced, so > + * avoid calling __pa() on it directly. > + */ > + return __pa(high_memory - 1); > +} > +static inline bool phys_addr_is_highmem(phys_addr_t addr) > +{ > + return addr > last_lowmem_paddr(); > +} > +
Are we sure that high_memory - 1 is always a valid reference? Consider especially the case where there is MMIO beyond end of memory on a system which has less RAM than the HIGHMEM boundary...
-hpa
-- H. Peter Anvin, Intel Open Source Technology Center I work for Intel. I don't speak on their behalf.
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