On 08/13/2012 12:21 PM, Marcelo Tosatti wrote: > On Wed, Aug 08, 2012 at 10:43:01AM +0800, Wen Congyang wrote: >> We can know the guest is panicked when the guest runs on xen. >> But we do not have such feature on kvm. >> >> Another purpose of this feature is: management app(for example: >> libvirt) can do auto dump when the guest is panicked. If management >> app does not do auto dump, the guest's user can do dump by hand if >> he sees the guest is panicked. >> >> We have three solutions to implement this feature: >> 1. use vmcall >> 2. use I/O port >> 3. use virtio-serial. >> >> We have decided to avoid touching hypervisor. The reason why I choose >> choose the I/O port is: >> 1. it is easier to implememt >> 2. it does not depend any virtual device >> 3. it can work when starting the kernel > > How about searching for the "Kernel panic - not syncing" string > in the guests serial output? Say libvirtd could take an action upon > that? > > Advantages: > - It works for all architectures. > - It does not depend on any virtual device. But it _does_ depend on a serial console, and furthermore requires libvirt to tee the serial console (right now, libvirt can treat the console as an opaque pass-through to the end user, but if you expect libvirt to parse the serial console for a particular string, you've lost some efficiency). > - It works as early as serial console output does (panics before > that should be rare). > - It allows you to see why the guest panicked. I think your arguments for a serial console have already been made and refuted in earlier versions of this patch series, which is WHY this series is still applicable. -- Eric Blake eblake@xxxxxxxxxx +1-919-301-3266 Libvirt virtualization library http://libvirt.org
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