Re: [Xen-users] svm.c:83:d917 Bad instruction length 0

["Trolle Selander" <trolle.selander@xxxxxxxxx>]

The easiest (*cough*) way is usually to put in some code before the domain_crash(curr->domain) that dumps the bytes around the eip, but of course that requires that you rebuild xen from source. One fairly painless thing that you could do to at least get a hint of what might be going on is to set in the VM configuration file. That way, after it's crashed, you can do an "xm debug-key v" and get some information about the last vmexit, which will at least tell us what type of instruction it was that caused the vmexit.

On Tue, Aug 5, 2008 at 1:39 AM, James Harper <james.harper@xxxxxxxxxxxxxxxx> wrote:

>
> In 3.2.2-rc2-pre, an instruction length of 0 doesn't cause a guest
crash,
> but rather a retry of the instruction. This was introduced in cs
16898.
> That said,  in 3.2 and older svm.c has a bunch of special case
emulation
> code for system instructions, some of which is quite
incomplete/incorrect.
> 3.3 will be much improved in this regard. In any case, a dump of the
> instruction bytes surrounding the eip would be necessary to determine
what
> the cause was in this particular case.
>

How easy is it to get that information?

The annoying thing in this case is that it worked under 3.1.[12].

Thanks

James

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