From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vitaly Kuznetsov Subject: Re: Using kexec-crashdump with recent Xen and Linux HVM Date: Wed, 11 Mar 2015 18:43:56 +0100 Message-ID: <87385bv38j.fsf@vitty.brq.redhat.com> References: <5500787F.8060709@canonical.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <5500787F.8060709@canonical.com> (Stefan Bader's message of "Wed, 11 Mar 2015 18:16:47 +0100") List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Stefan Bader Cc: "xen-devel@lists.xensource.com" List-Id: xen-devel@lists.xenproject.org Stefan Bader writes: > After being asked about this I started to play around with Xen-4.4.1/4.5 > together with HVM Linux guest running 3.13/3.16/3.19. With mixed success. > Usually rather failing. > > From a bit of research most activity to enable things were back in 2011. There > was a bit of a throwback around Linux 3.2[1] but it appears [2] restored this in > a backwards compatible way. Around 3.17 xen_nopv was introduced but I have not > figured out a helpful usage of this. > > The failure exhibits no visible messages in the guest after the crash stacktrace > caused by sysreq-trigger while 1vcpu seems to be in a spinning loop. On the host > side I noticed changing messages (TX queue drain or EVCHNOP errors). > > Command-line is a mix of nomodeset (to keep cirrusdrm away) and some defaults > from the kdump-tools (maxcpus=1 irqpoll nousb). > > The closest thing to success I can get to is using xen_emul_unplug=never for the > normal boot (which propagates into the kexec command). This of course stops > usage of the pv drivers. I also tried some variation of blacklisting the > emulated drivers and using xen_emul_unplug=unnecessary but that did not seem to > work for me. The crash-kexec boot without unplugging still fails to bring up the > NIC but at least finds the root disk to store the dump there. But not using the > pv drivers is not a setup one would want to have running just in case. > > So I was wondering whether I still miss something. No, kexec/kdump for PVHVM has well-known issues. You can start reading from http://lists.xen.org/archives/html/xen-devel/2014-12/msg01312.html I'm still going to pick this up eventually. > > -Stefan > > [1] commit 12275dd4b747f5d87fa36229774d76bca8e63068 > Revert "xen/pv-on-hvm kexec: add xs_reset_watches to shutdown watches..." > [2] commit cb6b6df111e46b9d0f79eb971575fd50555f43f4 > xen/pv-on-hvm kexec: add quirk for Xen 3.4 and shutdown watches. > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xen.org > http://lists.xen.org/xen-devel -- Vitaly