From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Cooper Subject: Re: [PATCH v2 01/11] kexec: introduce kexec_ops struct Date: Fri, 23 Nov 2012 01:56:08 +0000 Message-ID: <50AED7B8.7040902@citrix.com> 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> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <18e831d4-910d-4f58-8911-1398b96e3a47@email.android.com> Sender: linux-kernel-owner@vger.kernel.org To: "H. Peter Anvin" Cc: "Eric W. Biederman" , Daniel Kiper , "jbeulich@suse.com" , "konrad.wilk@oracle.com" , "mingo@redhat.com" , "tglx@linutronix.de" , "x86@kernel.org" , "kexec@lists.infradead.org" , "linux-kernel@vger.kernel.org" , "virtualization@lists.linux-foundation.org" , "xen-devel@lists.xensource.com" List-Id: xen-devel@lists.xenproject.org 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. For within-guest kexec/kdump functionality, I agree that it is barking mad. However, we do see cloud operators interested in the idea so VM administrators can look after their crashes themselves. ~Andrew