On 2012-08-14 16:55, Yan Vugenfirer wrote:

On Aug 14, 2012, at 1:42 PM, Jan Kiszka wrote:

quoted

On 2012-08-14 10:56, Daniel P. Berrange wrote:

quoted

On Mon, Aug 13, 2012 at 03:21:32PM -0300, Marcelo Tosatti wrote:

quoted

On Wed, Aug 08, 2012 at 10:43:01AM +0800, Wen Congyang wrote:

quoted

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?

No, this is not satisfactory. It depends on the guest OS being
configured to use the serial port for console output which we
cannot mandate, since it may well be required for other purposes.

Please don't forget Windows guests, there is no console and no "Kernel Panic" string ;)

What I used for debugging purposes on Windows guest is to register a bugcheck callback in virtio-net driver and write 1 to VIRTIO_PCI_ISR register.

What prevents writing the magic words to a second serial port in the
same way via that callback?

Jan

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