Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752776AbaJ2Eaj (ORCPT ); Wed, 29 Oct 2014 00:30:39 -0400 Received: from mail-pd0-f178.google.com ([209.85.192.178]:37841 "EHLO mail-pd0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752319AbaJ2Eag (ORCPT ); Wed, 29 Oct 2014 00:30:36 -0400 Date: Wed, 29 Oct 2014 12:30:30 +0800 From: Minfei Huang To: "H. Peter Anvin" Cc: Thomas Gleixner , mingo@redhat.com, x86@kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: Avoid overlap the fixmap area on i386 Message-ID: <20141029043030.GA4514@dhcp-17-62.nay.redhat.com> References: <6B680A9E-6CE9-4C96-934B-CB01DCB58278@gmail.com> <544FD138.3030305@zytor.com> <54505B7A.80502@zytor.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <54505B7A.80502@zytor.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/28/14 at 08:14pm, H. Peter Anvin wrote: > On 10/28/2014 10:29 AM, Thomas Gleixner wrote: > > On Tue, 28 Oct 2014, H. Peter Anvin wrote: > >> On 10/28/2014 04:06 AM, Thomas Gleixner wrote: > >>>> > >>>> The available address we can use is lower than FIXADDR_BOOT_START. So > >>>> We will set the kmap boundary below the FIXADDR_BOOT_START, if configure > >>>> the high memory. > >>>> > >>>> If we configure the high memory, the vmalloc reserve area should end > >>>> up to PKMAP_BASE, otherwise should end up to FIXADDR_BOOT_START. > >>> > >>> Which is not really a problem, because the FIXADDR_BOOT area is only > >>> used during boot for early_ioremap() and it's unused when ioremap() is > >>> functional. vmalloc becomes available after early boot so the > >>> FIXADDR_BOOT area is available for reuse. > >>> > >> > >> Given the very limited address space available on i386, it would be > >> extremely undesirable to not reuse address space when possible. > > > > Fair enough. Then we should do that for the highmem=y case as well. > > > > It is probably even more important for highmem=y... > > -hpa Agree. Maybe we can overlap the early_ioremap fix address to re-use it. Virtual address is more precious on i386, especially when turn on the high memory. I will post an patch to fix it. > > -- 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/