Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752818Ab2JGK1u (ORCPT ); Sun, 7 Oct 2012 06:27:50 -0400 Received: from terminus.zytor.com ([198.137.202.10]:32789 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751487Ab2JGK1o (ORCPT ); Sun, 7 Oct 2012 06:27:44 -0400 User-Agent: K-9 Mail for Android In-Reply-To: <50714881020000780008D43E@nat28.tlf.novell.com> References: <1349269157-25956-1-git-send-email-matt@console-pimps.org> <1349269157-25956-2-git-send-email-matt@console-pimps.org> <506C4C3A020000780008D041@nat28.tlf.novell.com> <506DFAD8.5060701@zytor.com> <506E9CDC020000780009FD13@nat28.tlf.novell.com> <506F0A90.7020106@zytor.com> <50714881020000780008D43E@nat28.tlf.novell.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Subject: Re: [PATCH 1/3] x86, mm: Include the entire kernel memory map in trampoline_pgd From: "H. Peter Anvin" Date: Sun, 07 Oct 2012 19:26:57 +0900 To: Jan Beulich CC: matt@console-pimps.org, matt.fleming@intel.com, mingo@kernel.org, x86@kernel.org, mjg@redhat.com, linux-efi@vger.kernel.org, linux-kernel@vger.kernel.org Message-ID: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1583 Lines: 45 Actually, no, because we may need to double-map in the low address space per discussion at LPC. Jan Beulich wrote: >>>> "H. Peter Anvin" 10/05/12 6:28 PM >>> >>On 10/04/2012 11:39 PM, Jan Beulich wrote: >>>> >>>> We should have the check, but at least for Linux support we require >>>> P <= V-2. >>> >>> Not really imo - P <= V - 1 should be sufficient here, as all that >is >>> necessary is that the result represents a 1:1 mapping. Specifically, >>> there's no constraint to the virtual space limitation of the direct >>> mapping of RAM. >>> >> >>The P <= V-2 limitation doesn't come from this, it comes from the fact > >>that we need to have the regular kernel 1:1 map and still have space >for >>the kernel, vmalloc, ioremap and so on in the kernel part of the >address >>space; in theory it *could* be some fraction between 1 and 2, but >since >>hardware doesn't do fractional bits very well the above is what we >have >>been telling the hardware folks. :) > >I understand all that, but here we're talking about a true 1:1 mapping >(i.e. in the lower half of the virtual address space), as opposed to >the >direct mapping (in the upper half). We can obviously use all of the >lower >half for this purpose. > >Jan -- 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/