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. <academic> 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 :) </academic> Laszlo -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list