From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx143.postini.com [74.125.245.143]) by kanga.kvack.org (Postfix) with SMTP id 54A3E6B0062 for ; Sun, 9 Sep 2012 13:01:39 -0400 (EDT) Message-ID: <504CCB6D.7070005@zytor.com> Date: Sun, 09 Sep 2012 10:01:33 -0700 From: "H. Peter Anvin" MIME-Version: 1.0 Subject: Re: mtd: kernel BUG at arch/x86/mm/pat.c:279! References: <1340959739.2936.28.camel@lappy> <1347057778.26695.68.camel@sbsiddha-desk.sc.intel.com> <1347062045.26695.82.camel@sbsiddha-desk.sc.intel.com> <1347202600.5876.7.camel@sbsiddha-ivb> In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Linus Torvalds Cc: suresh.b.siddha@intel.com, Sasha Levin , Andrew Morton , dwmw2@infradead.org, "linux-kernel@vger.kernel.org" , linux-mtd@lists.infradead.org, linux-mm , Dave Jones On 09/09/2012 08:31 AM, Linus Torvalds wrote: > On Sun, Sep 9, 2012 at 7:56 AM, Suresh Siddha wrote: >> >> yes but that is not a valid range I think because of the supported >> physical address bit limits of the processor and also the max >> architecture limit of 52 address bits. > > But how could the caller possibly know that? None of those internal > PAT limits are exposed anywhere. > > So doing the BUG_ON() is wrong. I'd suggest changing it to an EINVAL. > > In fact, BUG_ON() is *always* wrong, unless it's a "my internal data > structures are so messed up that I cannot continue". > I suspect the right answer is doing something like: u64 max_phys = 1ULL << boot_cpu_data.x86_phys_bits; if (start >= max_phys || end > max_phys || start >= end) return -EINVAL; ... although max_phys perhaps should be precalculated and stored in struct cpuinfo_x86 instead of being generated de novo. -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