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RE: [Xen-devel] [PATCH] Add tool to attempt to crash HVM guests

To: Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
Subject: RE: [Xen-devel] [PATCH] Add tool to attempt to crash HVM guests
From: Paul Durrant <Paul.Durrant@xxxxxxxxxx>
Date: Thu, 29 Jul 2010 17:12:16 +0100
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Thread-topic: [Xen-devel] [PATCH] Add tool to attempt to crash HVM guests
> -----Original Message-----
> From: Ian Jackson
> Sent: 29 July 2010 16:51
> To: Paul Durrant
> Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
> Subject: Re: [Xen-devel] [PATCH] Add tool to attempt to crash HVM
> guests
> 
> Paul Durrant writes ("[Xen-devel] [PATCH] Add tool to attempt to
> crash HVM guests"):
> > This tool reads the CPU save records, overwrites RIP with a bogus
> > value, and then restores them. This is, of course, not guaranteed
> > to crash the guest (since the CPUs may not be executing in kernel
> > at the time) but it's good for breaking into some tight loops that
> > would be hard to debug otherwise.
> 
> Surely there must be a better way of doing this!  Isn't it
> sufficient
> to pause the guest and then inspect it ?  Or do we need a new domctl
> to crash the guest explicitly ?
> 

Ian,

Inspecting the guest from dom0 is of limited use since we have nothing running 
there to attach windbg too. Causing it to fallover in the way this tool does 
usually unlocks the kernel debugger polling loop and hence windbg can get a 
lookin over the emulated serial device.
By 'crash the guest explicitly' what were you thinking?

  Paul

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