Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758296Ab2HWVYK (ORCPT ); Thu, 23 Aug 2012 17:24:10 -0400 Received: from terminus.zytor.com ([198.137.202.10]:57454 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756045Ab2HWVYG (ORCPT ); Thu, 23 Aug 2012 17:24:06 -0400 Message-ID: <50369F67.8040101@zytor.com> Date: Thu, 23 Aug 2012 14:23:51 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:13.0) Gecko/20120605 Thunderbird/13.0 MIME-Version: 1.0 To: Konrad Rzeszutek Wilk CC: Jacob Shin , X86-ML , LKML , Yinghai Lu , Andreas Herrmann , Tejun Heo , Borislav Petkov , Dave Young , Chao Wang , Vivek Goyal Subject: Re: [PATCH 3/4] x86: Only direct map addresses that are marked as E820_RAM References: <1344983957-4996-1-git-send-email-jacob.shin@amd.com> <1344983957-4996-4-git-send-email-jacob.shin@amd.com> <50356BA9.5030906@zytor.com> <20120823145043.GA4671@jshin-Toonie> <50364E9E.6020104@zytor.com> <20120823201224.GA24203@phenom.dumpdata.com> In-Reply-To: <20120823201224.GA24203@phenom.dumpdata.com> X-Enigmail-Version: 1.4.3 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1158 Lines: 30 On 08/23/2012 01:12 PM, Konrad Rzeszutek Wilk wrote: >> >> Okay... I think I need to grok that a bit better. For memory >> allocations, we probably should just use brk allocations, for >> virtual space allocations it is called the fixmap for a reason (even >> though the Xen people managed to break that on 32 bits, sigh!) > > Can you rope me in on that? Was that added ooh years ago ? Yeah, it dates back to the original paravirt work. The issue is that Xen likes to live at the top of the virtual address space, which is where the fixmap lives. Suddenly the fixmap is no longer at a fixed address, which was sort of the whole idea. The problem is that on i386 there are very few unmovable boundaries left in the virtual address space. The only other one left, really, is at the very beginning of kernel space. At this point people's appetite for large changes on 32 bits is limited, of course. -hpa -- 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/