From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1161048Ab2KWJwq (ORCPT ); Fri, 23 Nov 2012 04:52:46 -0500 Received: from nat28.tlf.novell.com ([130.57.49.28]:37253 "EHLO nat28.tlf.novell.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1161014Ab2KWJwo convert rfc822-to-8bit (ORCPT ); Fri, 23 Nov 2012 04:52:44 -0500 Message-Id: <50AF55B102000078000AABF3@nat28.tlf.novell.com> X-Mailer: Novell GroupWise Internet Agent 12.0.1 Date: Fri, 23 Nov 2012 09:53:37 +0000 From: "Jan Beulich" To: "Andrew Cooper" , "H. Peter Anvin" Cc: "x86@kernel.org" , "tglx@linutronix.de" , "kexec@lists.infradead.org" , "virtualization@lists.linux-foundation.org" , "xen-devel@lists.xensource.com" , "Daniel Kiper" , "konrad.wilk@oracle.com" , "mingo@redhat.com" , "linux-kernel@vger.kernel.org" , "Eric W. Biederman" Subject: Re: [PATCH v2 01/11] kexec: introduce kexec_ops struct References: <1353423893-23125-1-git-send-email-daniel.kiper@oracle.com> <1353423893-23125-2-git-send-email-daniel.kiper@oracle.com> <87lidwtego.fsf@xmission.com> <20121121105221.GA2925@host-192-168-1-59.local.net-space.pl> <87txshx28b.fsf@xmission.com> <50AE6542.3020302@zytor.com> <50AEBF86.50501@citrix.com> <18e831d4-910d-4f58-8911-1398b96e3a47@email.android.com> <50AED7B8.7040902@citrix.com> In-Reply-To: <50AED7B8.7040902@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 8BIT Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org >>> On 23.11.12 at 02:56, Andrew Cooper wrote: > On 23/11/2012 01:38, H. Peter Anvin wrote: >> I still don't really get why it can't be isolated from dom0, which would > make more sense to me, even for a Xen crash. >> > > The crash region (as specified by crashkernel= on the Xen command line) > is isolated from dom0. > > dom0 (using the kexec utility etc) has the task of locating the Xen > crash notes (using the kexec hypercall interface), constructing a binary > blob containing kernel, initram and gubbins, and asking Xen to put this > blob in the crash region (again, using the kexec hypercall interface). > > I do not see how this is very much different from the native case > currently (although please correct me if I am misinformed). Linux has > extra work to do by populating /proc/iomem with the Xen crash regions > boot (so the kexec utility can reference their physical addresses when > constructing the blob), and should just act as a conduit between the > kexec system call and the kexec hypercall to load the blob. But all of this _could_ be done completely independent of the Dom0 kernel's kexec infrastructure (i.e. fully from user space, invoking the necessary hypercalls through the privcmd driver). It's just that parts of the kexec infrastructure can be re-used (and hence that mechanism probably seemed the easier approach to the implementer of the original kexec-on-Xen). If the kernel folks dislike that re-use (quite understandably looking at how much of it needs to be re-done), that shouldn't prevent us from looking into the existing alternatives. Jan