Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752305Ab3DOEx3 (ORCPT ); Mon, 15 Apr 2013 00:53:29 -0400 Received: from fgwmail5.fujitsu.co.jp ([192.51.44.35]:33884 "EHLO fgwmail5.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751944Ab3DOEx2 (ORCPT ); Mon, 15 Apr 2013 00:53:28 -0400 X-SecurityPolicyCheck: OK by SHieldMailChecker v1.8.9 X-SHieldMailCheckerPolicyVersion: FJ-ISEC-20120718-2 Message-ID: <516B87A6.9080708@jp.fujitsu.com> Date: Mon, 15 Apr 2013 13:52:54 +0900 From: HATAYAMA Daisuke User-Agent: Mozilla/5.0 (Windows NT 5.1; rv:17.0) Gecko/20130328 Thunderbird/17.0.5 MIME-Version: 1.0 To: Dave Hansen CC: "H. Peter Anvin" , "kexec@lists.infradead.org" , Linux Kernel Mailing List , Cliff Wickman , Simon Horman , "Eric W. Biederman" , Yinghai Lu , Thomas Renninger , Vivek Goyal Subject: Re: [PATCH 5/5] kexec: X86: Pass memory ranges via e820 table instead of memmap= boot parameter References: <1365683207-42425-1-git-send-email-trenn@suse.de> <1365683207-42425-6-git-send-email-trenn@suse.de> <5166D18A.7090800@zytor.com> <20130412143104.GA4301@redhat.com> <5168208B.7050107@zytor.com> <51688803.8020401@sr71.net> In-Reply-To: <51688803.8020401@sr71.net> Content-Type: text/plain; charset=ISO-8859-1; 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: 39 (2013/04/13 7:17), Dave Hansen wrote: > On 04/12/2013 07:56 AM, H. Peter Anvin wrote: >> On 04/12/2013 07:31 AM, Vivek Goyal wrote: >>>> I also have to admit that I don't see the difference between /dev/mem >>>> and /dev/oldmem, as the former allows access to memory ranges outside >>>> the ones used by the current kernel, which is what the oldmem device >>>> seems to be intended to od. > > It varies from arch to arch of course. > > But, /dev/mem has restrictions on it, like CONFIG_STRICT_DEVMEM or the > ARCH_HAS_VALID_PHYS_ADDR_RANGE. There's a lot of stuff that depends on > it, *and* folks have tried to fix it up so that it's not _as_ blatant of > a way to completely screw your system. > > /dev/mem also tries to be nice to arches that have restrictions like: > >> /* >> * On ia64 if a page has been mapped somewhere as >> * uncached, then it must also be accessed uncached >> * by the kernel or data corruption may occur >> */ > > I think /dev/oldmem isn't so nice and could actually cause some real > problems if used on ia64 where the cached/uncached accesses are mixed. This sounds like there's no such issue on x86 cache mechanism. Is it correct? If so, what is the difference between ia64 and x86 cache mechanisms? -- Thanks. HATAYAMA, Daisuke -- 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/