From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chris Lalancette Subject: Re: [PATCH 5/5] Fix kdump under KVM. Date: Wed, 28 Oct 2009 11:21:42 +0100 Message-ID: <4AE81B36.5010104@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> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: kvm@vger.kernel.org To: Marcelo Tosatti Return-path: Received: from mx1.redhat.com ([209.132.183.28]:56141 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752719AbZJ1KVj (ORCPT ); Wed, 28 Oct 2009 06:21:39 -0400 Received: from int-mx04.intmail.prod.int.phx2.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.17]) by mx1.redhat.com (8.13.8/8.13.8) with ESMTP id n9SALi63005801 for ; Wed, 28 Oct 2009 06:21:44 -0400 In-Reply-To: <20091027174246.GA10473@amt.cnet> Sender: kvm-owner@vger.kernel.org List-ID: Marcelo Tosatti wrote: > On Tue, Oct 27, 2009 at 05:41:07PM +0100, Chris Lalancette wrote: >> This patch is the main point of the series. In order for >> kdump to properly work inside a KVM guest, we need to make >> sure that all VCPUs in virtual wire APIC mode get kicked >> to try and pick up the timer interrupts. To do this, >> we iterate over the CPUs and deliver interrupts to the >> proper VCPUs. >> >> I don't love the concept of doing kvm_irq_kick_vcpus() from >> within pit_timer_fn(). A PIT is not connected to a CPU at all, >> only to a PIC or APIC. However, if a CPU enters idle, this is >> the only way to wake it up to check for the interrupt. > > The reason the PIT interrupt was fixed to BSP is: > > http://www.mail-archive.com/kvm-devel@lists.sourceforge.net/msg13250.html > > Perhaps enhancing ioapic_deliver's (irq == 0) check to bypass the > destination overwrite in case its programmed by the guest to > a single CPU would fix it? Ug, nasty. I definitely don't want to re-introduce that bug. What exactly do you mean by "fix it"? Do you mean fix the original RHEL-5.1 PAE issue, or fix the kdump issue? -- Chris Lalancette