From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH 5/5] Fix kdump under KVM. Date: Sun, 01 Nov 2009 17:21:23 +0200 Message-ID: <4AEDA773.7030906@redhat.com> References: <1256661667-9298-1-git-send-email-clalance@redhat.com> <1256661667-9298-6-git-send-email-clalance@redhat.com> <20091027174246.GA10473@amt.cnet> <4AE81B36.5010104@redhat.com> <20091028124100.GA3063@amt.cnet> <4AEADADD.7070501@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Marcelo Tosatti , kvm@vger.kernel.org To: Chris Lalancette Return-path: Received: from mx1.redhat.com ([209.132.183.28]:33074 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752621AbZKAPVU (ORCPT ); Sun, 1 Nov 2009 10:21:20 -0500 Received: from int-mx08.intmail.prod.int.phx2.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.21]) by mx1.redhat.com (8.13.8/8.13.8) with ESMTP id nA1FLPF0021605 for ; Sun, 1 Nov 2009 10:21:25 -0500 In-Reply-To: <4AEADADD.7070501@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On 10/30/2009 02:23 PM, Chris Lalancette wrote: > In the meantime, I've gotten the "set_irq from IRQ context" that Avi > suggested > working, and the fixing up of this IOAPIC check is the last bit to actually get > kdump working. > There are two problems with that: - kvm_set_irq() calls some notifiers (irq_mask_notifiers, at least, but possibly more); need to make sure those are safe from irq context - kvm_set_irq() will loop on all vcpus, usually incurring a cache miss or two; with large vcpu counts this can make the irq-off time quite large, hurting our worst-case latency we can defer the second problem since it's only a performance issue, but how did you deal with the first? -- error compiling committee.c: too many arguments to function