Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753785Ab3DLXSi (ORCPT ); Fri, 12 Apr 2013 19:18:38 -0400 Received: from terminus.zytor.com ([198.137.202.10]:60948 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752577Ab3DLXSh (ORCPT ); Fri, 12 Apr 2013 19:18:37 -0400 User-Agent: K-9 Mail for Android In-Reply-To: <51688803.8020401@sr71.net> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Subject: Re: [PATCH 5/5] kexec: X86: Pass memory ranges via e820 table instead of memmap= boot parameter From: "H. Peter Anvin" Date: Fri, 12 Apr 2013 16:17:17 -0700 To: Dave Hansen CC: Vivek Goyal , Yinghai Lu , Thomas Renninger , Simon Horman , "kexec@lists.infradead.org" , "Eric W. Biederman" , Cliff Wickman , Linux Kernel Mailing List Message-ID: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1585 Lines: 43 Yes... That is one reason I think it is a real problem. 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. -- Sent from my mobile phone. Please excuse brevity and lack of formatting. -- 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/