Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753554AbbKXM5H (ORCPT ); Tue, 24 Nov 2015 07:57:07 -0500 Received: from mx2.suse.de ([195.135.220.15]:54062 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753431AbbKXM5F convert rfc822-to-8bit (ORCPT ); Tue, 24 Nov 2015 07:57:05 -0500 Date: Tue, 24 Nov 2015 13:57:01 +0100 From: Petr Tesarik To: Andrew Cooper Cc: David Vrabel , Malcolm Crossley , Jan Beulich , Daniel Kiper , Juergen Gross , , , , , , David Mair , , , Subject: Re: [Xen-devel] crash tool - problem with new Xen linear virtual mapped sparse p2m list Message-ID: <20151124135701.1d75c901@hananiah.suse.cz> In-Reply-To: <56543D57.2030903@citrix.com> References: <20151123201830.GN4768@olila.local.net-space.pl> <565409DA.90908@suse.com> <565434F102000078000B8424@prv-mh.provo.novell.com> <56543412.7090104@citrix.com> <5654373D.9070403@citrix.com> <20151124111725.4f45412e@hananiah.suse.cz> <56543D57.2030903@citrix.com> Organization: SUSE Linux, s.r.o. X-Mailer: Claws Mail 3.11.0 (GTK+ 2.24.28; x86_64-suse-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2214 Lines: 48 V Tue, 24 Nov 2015 10:35:03 +0000 Andrew Cooper napsáno: > On 24/11/15 10:17, Petr Tesarik wrote: > > On Tue, 24 Nov 2015 10:09:01 +0000 > > David Vrabel wrote: > > > >> On 24/11/15 09:55, Malcolm Crossley wrote: > >>> On 24/11/15 08:59, Jan Beulich wrote: > >>>>>>> On 24.11.15 at 07:55, wrote: > >>>>> What about: > >>>>> > >>>>> 4) Instead of relying on the kernel maintained p2m list for m2p > >>>>> conversion use the hypervisor maintained m2p list which should be > >>>>> available in the dump as well. This is the way the alive kernel is > >>>>> working, so mimic it during crash dump analysis. > >>>> I fully agree; I have to admit that looking at the p2m when doing page > >>>> table walks for a PV Dom0 (having all machine addresses in page table > >>>> entries) seems kind of backwards. (But I say this knowing nothing > >>>> about the tool.) > >>>> > >>> I don't think we can reliably use the m2p for PV domains because > >>> PV domains don't always issue a m2p update hypercall when they change > >>> their p2m mapping. > >> This only applies to foreign pages which won't be very interesting to a > >> crash tool. > > True. I think the main reason crash hasn't done this is that it cannot > > find the hypervisor maintained m2p list. It should be sufficient to add > > some more fields to XEN_VMCOREINFO, so that crash can locate the > > mapping in the dump. > > The M2P lives at an ABI-specified location in all virtual address spaces > for PV guests. > > Either 0xF5800000 or 0xFFFF800000000000 depending on bitness. Hm, this is nice, but kind of chicken-and-egg problem. A system dump contains a snapshot of the machine's RAM. But the addresses you mentioned are virtual addresses. How do I translate them to physical addresses without an m2p mapping? I need at least the value of CR3 for that domain, and most likely a way to determine if it is a PV domain. Petr T -- 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/