Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754133AbbKXKfK (ORCPT ); Tue, 24 Nov 2015 05:35:10 -0500 Received: from smtp02.citrix.com ([66.165.176.63]:44245 "EHLO SMTP02.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753028AbbKXKfH (ORCPT ); Tue, 24 Nov 2015 05:35:07 -0500 X-IronPort-AV: E=Sophos;i="5.20,338,1444694400"; d="scan'208";a="320341793" Message-ID: <56543D57.2030903@citrix.com> Date: Tue, 24 Nov 2015 10:35:03 +0000 From: Andrew Cooper User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Icedove/31.8.0 MIME-Version: 1.0 To: Petr Tesarik , David Vrabel CC: 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 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> In-Reply-To: <20151124111725.4f45412e@hananiah.suse.cz> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit X-DLP: MIA1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1820 Lines: 42 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. This will be more compatible to use, as it won't depend on a newer hypervisor with modified notes. ~Andrew -- 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/