Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932355AbWEUJws (ORCPT ); Sun, 21 May 2006 05:52:48 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932357AbWEUJws (ORCPT ); Sun, 21 May 2006 05:52:48 -0400 Received: from smtp.osdl.org ([65.172.181.4]:25984 "EHLO smtp.osdl.org") by vger.kernel.org with ESMTP id S932355AbWEUJwr (ORCPT ); Sun, 21 May 2006 05:52:47 -0400 Date: Sun, 21 May 2006 02:52:22 -0700 From: Andrew Morton To: Rusty Russell Cc: zach@vmware.com, virtualization@lists.osdl.org, torvalds@osdl.org, mingo@elte.hu, linux-kernel@vger.kernel.org Subject: Re: [patch] i386, vdso=[0|1] boot option and /proc/sys/vm/vdso_enabled Message-Id: <20060521025222.1e2790f0.akpm@osdl.org> In-Reply-To: <1148204118.31087.8.camel@localhost.localdomain> References: <1147759423.5492.102.camel@localhost.localdomain> <20060516064723.GA14121@elte.hu> <1147852189.1749.28.camel@localhost.localdomain> <20060519174303.5fd17d12.akpm@osdl.org> <20060520010303.GA17858@elte.hu> <20060519181125.5c8e109e.akpm@osdl.org> <20060520085351.GA28716@elte.hu> <20060520022650.46b048f8.akpm@osdl.org> <446EE1C2.7060400@vmware.com> <20060520024842.69c77aaf.akpm@osdl.org> <446EE992.4020604@vmware.com> <1148186298.29161.8.camel@localhost.localdomain> <1148204118.31087.8.camel@localhost.localdomain> X-Mailer: Sylpheed version 1.0.4 (GTK+ 1.2.10; i386-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1103 Lines: 25 Rusty Russell wrote: > > Hypervisors want to use memory at the top of the address space > (eg. 64MB for Xen, or 168MB for Xen w/ PAE). Creating this hole means > moving the vsyscall page away from 0xffffe000. > > If we create this hole statically with a config option, we give up, > say, 256MB of lowmem for the case where a hypervisor-capable kernel is > actually running on native hardware. > > If we create this hole dynamically and leave the vsyscall page at the > top of kernel memory, we would have to patch up the vsyscall elf > header at boot time to reflect where we put it. > > Instead, this patch moves the vsyscall page into the user address > region, just below PAGE_OFFSET: it's still at a fixed address, but > it's not where the hypervisor wants to be, so resizing the hole is > trivial. Seems to work. - 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/