Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754356Ab2JFAgZ (ORCPT ); Fri, 5 Oct 2012 20:36:25 -0400 Received: from terminus.zytor.com ([198.137.202.10]:43131 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752948Ab2JFAgX (ORCPT ); Fri, 5 Oct 2012 20:36:23 -0400 Message-ID: <506F7CF5.2070904@zytor.com> Date: Fri, 05 Oct 2012 17:36:05 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:15.0) Gecko/20120911 Thunderbird/15.0.1 MIME-Version: 1.0 To: "Eric W. Biederman" CC: Yinghai Lu , Konrad Rzeszutek Wilk , Jacob Shin , Stefano Stabellini , Thomas Gleixner , Ingo Molnar , Tejun Heo , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH 04/13] x86, mm: Revert back good_end setting for 64bit References: <1348991844-12285-1-git-send-email-yinghai@kernel.org> <1348991844-12285-5-git-send-email-yinghai@kernel.org> <20121003165105.GA30214@jshin-Toonie> <20121004164630.GB2244@phenom.dumpdata.com> <871uhcsk93.fsf@xmission.com> <87ehlcr4et.fsf@xmission.com> <506F78A2.3050408@zytor.com> <87zk40mokt.fsf@xmission.com> In-Reply-To: <87zk40mokt.fsf@xmission.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1641 Lines: 45 On 10/05/2012 05:28 PM, Eric W. Biederman wrote: >> >> Seriously, any case where we can't load anywhere in physical ram on x86-64 is a >> bug. i386 is another matter. > > As I recall there are data structures like the IDT that only have a > 32bit base address. > Not true. The only one I know of is memory for the trampoline which has to be below 1M. The < 1M space is already handled specially for good reason. > According to the bzImage header we don't support ramdisks above 4G. > I think we also have a 32bit address for the kernel command line > in the bzImage header. There are pointers in the bzImage header, that is true. We can fix that problem, though, at least for entry via the 64-bit entry point. > In the case of kdump in particular there is a need for DMAable > memory and in general that means memory below 4G. So as long > as we only support one memory extent for kdump it makes sense > for that segment to be below 4G. "In general" meaning "no iotlb"? In that case you have some unknown address space restriction which may or may not be 4G... > For a normal x86_64 kernel which gets to use most of the memory it > definitely should be loadable anywhere in memory. Yes. We should fix problems, like the limitations in the boot_params structure. -hpa -- H. Peter Anvin, Intel Open Source Technology Center I work for Intel. I don't speak on their behalf. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/