From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:45244) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VCSBp-00043c-Kk for qemu-devel@nongnu.org; Thu, 22 Aug 2013 06:32:35 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1VCSBj-0006gA-Lt for qemu-devel@nongnu.org; Thu, 22 Aug 2013 06:32:29 -0400 Message-ID: <5215E946.5030008@redhat.com> Date: Thu, 22 Aug 2013 12:34:46 +0200 From: Laszlo Ersek MIME-Version: 1.0 References: <1377086477-19553-1-git-send-email-pbonzini@redhat.com> <5214DB87.6010305@redhat.com> <5214DD8B.2020803@redhat.com> <5215CDFB.7000201@redhat.com> <5215D7B0.5090500@redhat.com> In-Reply-To: <5215D7B0.5090500@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH] vl: allow "cont" from panicked state List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paolo Bonzini Cc: pkrempa@redhat.com, marcel.a@redhat.com, libvir-list@redhat.com, hutao@cn.fujitsu.com, qemu-stable@nongnu.org, mst@redhat.com, qemu-devel@nongnu.org, lcapitulino@redhat.com, rhod@redhat.com, kraxel@redhat.com, anthony@codemonkey.ws, afaerber@suse.de On 08/22/13 11:19, Paolo Bonzini wrote: > Il 22/08/2013 10:38, Laszlo Ersek ha scritto: >>>> To support 1.5, libvirt should simply be ready to react to unanticipated >>>> GUEST_PANICKED events. reboot-on-panic will simply be broken for 1.5 >>>> and Linux 3.10+ guests. :( >> I'm probably misunderstanding the discussion, but it might be possible >> to disable pvpanic even in 1.5 from the host side, with the following hack: >> >> -global pvpanic.ioport=0 >> >> In qemu, this will either configure a working pvpanic device on ioport >> 0, or the pvpanic device will be genuinely broken. At least it doesn't >> (obviously) break other stuff (in v1.5.2): >> >> (qemu) info mtree >> I/O >> 0000000000000000-000000000000ffff (prio 0, RW): io >> 0000000000000000-0000000000000000 (prio 0, RW): pvpanic >> 0000000000000000-0000000000000007 (prio 0, RW): dma-chan > > No, you're not misunderstanding the discussion. > > Depending on the priorities of the pvpanic and legacy-DMA regions, it > would break DMA channel 0. I think before priority comes into the picture, the access size would matter first, no? (I think I'm recalling this from the 0xCF9 reset control register, which falls into the [0xCF8..0xCFA] range.) Unless ioport 0 is accessed with width 1 for dma-chan purposes, I think such an access would be unique to pvpanic, and always dispatched to pvpanic. > Channel 0 is (was) used for DRAM refresh, so > it should not have any visible effect. However, it may not be entirely > disabling pvpanic, just making it mostly invisible. That's good enough for the guest to reach kexec :) Laszlo