From mboxrd@z Thu Jan 1 00:00:00 1970 From: linas@austin.ibm.com (Linas Vepstas) Subject: Re: [PATCH] ehea: Add kdump support Date: Mon, 26 Nov 2007 12:11:49 -0600 Message-ID: <20071126181148.GF4551@austin.ibm.com> References: <200711091433.51259.osstklei@de.ibm.com> <1196064988.19855.15.camel@concordia> <1196091697.7513.30.camel@luke-laptop.br.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: michael@ellerman.id.au, Michael Neuling , Jeff Garzik , Jan-Bernd Themann , netdev , linux-kernel , Thomas Klein , linux-ppc , Christoph Raisch , Paul Mackerras , Marcus Eder , Stefan Roscher , ahuja@austin.ibm.com To: Luke Browning Return-path: Received: from e32.co.us.ibm.com ([32.97.110.150]:55979 "EHLO e32.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751714AbXKZSMJ (ORCPT ); Mon, 26 Nov 2007 13:12:09 -0500 Content-Disposition: inline In-Reply-To: <1196091697.7513.30.camel@luke-laptop.br.ibm.com> Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org Hi, On Mon, Nov 26, 2007 at 01:41:37PM -0200, Luke Browning wrote: > On Mon, 2007-11-26 at 19:16 +1100, Michael Ellerman wrote: > > > For kdump we have to assume that the kernel is fundamentally broken, If I may so humbly suggest: since ehea is a power6 thing only, we should refocus our energies on "hypervisor assisted dump", which solves all of these problems. In short, upon crash, the hypervisor will reset the pci devices into working order, and will then boot a new fresh kernel into a tiny corner of ram. The rest of ram is not cleared, and can be dumped. After the dump, the mem is returned to general use. The key point here, for ehea, is "the hypervisor will reset he device state to something rational". Preliminary patches are at http://patchwork.ozlabs.org/linuxppc/patch?id=14884 and following. --linas