On Tue, Aug 14, 2012 at 01:53:01PM -0500, Anthony Liguori wrote:

Marcelo Tosatti [off-list ref] writes:

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On Tue, Aug 14, 2012 at 05:55:54PM +0300, Yan Vugenfirer wrote:

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

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

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

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

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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.

Yan. 

Considering whether a "panic-device" should cover other OSes is also \

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something to consider. Even for Linux, is "panic" the only case which
should be reported via the mechanism? What about oopses without panic? 

Is the mechanism general enough for supporting new events, etc.

Hi,

I think this discussion is gone of the deep end.

Forget about !x86 platforms.  They have their own way to do this sort of
thing.  

The panic function in kernel/panic.c has the following options, which
appear to be arch independent, on panic:

- reboot 
- blink

None are paravirtual interfaces however.

Think of this feature like a status LED on a motherboard.  These
are very common and usually controlled by IO ports.

We're simply reserving a "status LED" for the guest to indicate that it
has paniced.  Let's not over engineer this.

My concern is that you end up with state that is dependant on x86.

Subject: [PATCH v8 3/6] add a new runstate: RUN_STATE_GUEST_PANICKED

Having the ability to stop/restart the guest (and even introducing a 
new VM runstate) is more than a status LED analogy.

Can this new infrastructure be used by other architectures?

Do you consider allowing support for Windows as overengineering?

Regards,

Anthony Liguori

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Well, we have more than a single serial port, even when leaving
virtio-serial aside...

Jan

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Siemens AG, Corporate Technology, CT RTC ITP SDP-DE
Corporate Competence Center Embedded Linux
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