From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx177.postini.com [74.125.245.177]) by kanga.kvack.org (Postfix) with SMTP id 2D6596B0002 for ; Fri, 8 Feb 2013 15:50:30 -0500 (EST) Message-ID: <51156507.50900@zytor.com> Date: Fri, 08 Feb 2013 12:50:15 -0800 From: "H. Peter Anvin" MIME-Version: 1.0 Subject: Re: [PATCH 1/2] add helper for highmem checks References: <20130208202813.62965F25@kernel.stglabs.ibm.com> In-Reply-To: <20130208202813.62965F25@kernel.stglabs.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Dave Hansen Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, bp@alien8.de, mingo@kernel.org, tglx@linutronix.de 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. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org