From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758244Ab2HURhq (ORCPT ); Tue, 21 Aug 2012 13:37:46 -0400 Received: from rcsinet15.oracle.com ([148.87.113.117]:38091 "EHLO rcsinet15.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758045Ab2HURhn (ORCPT ); Tue, 21 Aug 2012 13:37:43 -0400 Date: Tue, 21 Aug 2012 13:27:32 -0400 From: Konrad Rzeszutek Wilk To: Stefano Stabellini , JBeulich@suse.com Cc: "linux-kernel@vger.kernel.org" , "xen-devel@lists.xensource.com" Subject: Q:pt_base in COMPAT mode offset by two pages. Was:Re: [Xen-devel] [PATCH 02/11] xen/x86: Use memblock_reserve for sensitive areas. Message-ID: <20120821172732.GA23715@phenom.dumpdata.com> References: <1345133009-21941-1-git-send-email-konrad.wilk@oracle.com> <1345133009-21941-3-git-send-email-konrad.wilk@oracle.com> <20120820141305.GA2713@phenom.dumpdata.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120820141305.GA2713@phenom.dumpdata.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-Source-IP: ucsinet22.oracle.com [156.151.31.94] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Aug 20, 2012 at 10:13:05AM -0400, Konrad Rzeszutek Wilk wrote: > On Fri, Aug 17, 2012 at 06:35:12PM +0100, Stefano Stabellini wrote: > > On Thu, 16 Aug 2012, Konrad Rzeszutek Wilk wrote: > > > instead of a big memblock_reserve. This way we can be more > > > selective in freeing regions (and it also makes it easier > > > to understand where is what). > > > > > > [v1: Move the auto_translate_physmap to proper line] > > > [v2: Per Stefano suggestion add more comments] > > > Signed-off-by: Konrad Rzeszutek Wilk > > > > much better now! > > Thought interestingly enough it breaks 32-bit dom0s (and only dom0s). > Will have a revised patch posted shortly. Jan, I thought something odd. Part of this code replaces this: memblock_reserve(__pa(xen_start_info->mfn_list), xen_start_info->pt_base - xen_start_info->mfn_list); with a more region-by-region area. What I found out that if I boot this as 32-bit guest with a 64-bit hypervisor the xen_start_info->pt_base is actually wrong. Specifically this is what bootup says: (good working case - 32bit hypervisor with 32-bit dom0): (XEN) Loaded kernel: c1000000->c1a23000 (XEN) Init. ramdisk: c1a23000->cf730e00 (XEN) Phys-Mach map: cf731000->cf831000 (XEN) Start info: cf831000->cf83147c (XEN) Page tables: cf832000->cf8b5000 (XEN) Boot stack: cf8b5000->cf8b6000 (XEN) TOTAL: c0000000->cfc00000 [ 0.000000] PT: cf832000 (f832000) [ 0.000000] Reserving PT: f832000->f8b5000 And with a 64-bit hypervisor: XEN) VIRTUAL MEMORY ARRANGEMENT: (XEN) Loaded kernel: 00000000c1000000->00000000c1a23000 (XEN) Init. ramdisk: 00000000c1a23000->00000000cf730e00 (XEN) Phys-Mach map: 00000000cf731000->00000000cf831000 (XEN) Start info: 00000000cf831000->00000000cf8314b4 (XEN) Page tables: 00000000cf832000->00000000cf8b6000 (XEN) Boot stack: 00000000cf8b6000->00000000cf8b7000 (XEN) TOTAL: 00000000c0000000->00000000cfc00000 (XEN) ENTRY ADDRESS: 00000000c16bb22c [ 0.000000] PT: cf834000 (f834000) [ 0.000000] Reserving PT: f834000->f8b8000 So the pt_base is offset by two pages. And looking at c/s 13257 its not clear to me why this two page offset was added? The toolstack works fine - so launching 32-bit guests either under a 32-bit hypervisor or 64-bit works fine: ] domainbuilder: detail: xc_dom_alloc_segment: page tables : 0xcf805000 -> 0xcf885000 (pfn 0xf805 + 0x80 pages) [ 0.000000] PT: cf805000 (f805000)