Re: 64 bit Intel HVM Weirdness - setjmp\longjump fp exception in Xen, not on real hardware or AMD HVM

[Allan Graves <allan.graves@oracle.com>]

Keir,

Thank you.  Umm... I guess I wasn't sure exactly what the changelog 
should say - but clearly something other than what I would have titled 
it.  Which is probably cause I don't think I could have fixed the bug. :)

In any case, 3.4.1 does fix the issue!

Thank you so much for helping me through this!

Allan



Keir Fraser wrote:
> Well, what would you expect the changelog to say? It's fixed in the
> xen-3.4-testing.hg repository by changeset 19697, which is a backport of
> xen-unstable.hg:19953.
> 
>  -- Keir
> 
> On 01/11/2009 19:32, "Allan Graves" <allan.graves@oracle.com> wrote:
> 
>> Keir -
>>
>> Hmm... according to /sys/hypervisor/version, I'm running 3.4.0.
>>
>> Is there a reasonable chance this is fixed in 3.4.1?  I haven't seen
>> anything in the changelogs...
>>
>>
>> Allan
>>
>>
>>
>> Keir Fraser wrote:
>>> What version of Xen are you using? This bug may be fixed in Xen 3.3.2 and
>>> Xen 3.4.1.
>>>
>>>  -- Keir
>>>
>>> On 30/10/2009 01:23, "Allan Graves" <allan.graves@oracle.com> wrote:
>>>
>>>   
>>>> (Please excuse double posting - I was told xen-users was not the right
>>>> list, to put it on xen-devel, as it was not a technical support query,
>>>> but an issue.)
>>>>
>>>>
>>>> The following program will crash with a fp exception on an INTEL 64 bit
>>>> HVM domU only:
>>>> #include <setjmp.h>
>>>> jmp_buf env; main() { if(setjmp(env)) return; longjmp(env, 1); }
>>>>
>>>>
>>>> This can be seen using both Linux and Windows 64 bit Guests.
>>>>
>>>>
>>>> My machine is a Core 2 Duo with both VT-D and VT-X extensions enabled.
>>>> Unfortunately, this is blocking our usage of 64 bit HVM Windows guests.
>>>>
>>>> A similar issue was reported in KVM and recently fixed, some of their
>>>> analysis is below:
>>>> --------------------------------------------------
>>>>     
>>>>>>> It seems that the problem can be reproduced by compiling the
>>>>>>> following simple program using cygwin's gcc. The program crashes on
>>>>>>> w2k3-amd64 on kvm-83 on core2-duo, and it does not crash on the
>>>>>>> same w2k3-amd64 installation on kvm-83 on AMD Phenom.
>>>>>>>
>>>>>>> #include <setjmp.h>
>>>>>>>
>>>>>>> jmp_buf env; main() { if(setjmp(env)) return; longjmp(env, 1); }
>>>>>>>
>>>>>>> The problem seems to be in the instruction ``mov gs,ax'' (Intel
>>>>>>> syntax) in the longjmp() code. If I let the virtual machine execute
>>>>>>> the instruction, the program crashes. However, if I step over the
>>>>>>> instruction using the vs2008 debugger, the program completes
>>>>>>> without crashing. Thus, I think that this is the instruction that
>>>>>>> Avi is looking for, but I don't know how to proceed from here.
>>>>>>> -------------------------------------------------------
>>>>>>>           
>>>> http://markmail.org/message/owy3x7pf6oywdx5e#query:+page:1+mid:spz6vmdothb2n
>>>> jf
>>>> b+state:results
>>>>
>>>>
>>>>
>>>> Anyone have a solution to this? :)
>>>>
>>>> Allan
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> _______________________________________________
>>>> Xen-devel mailing list
>>>> Xen-devel@lists.xensource.com
>>>> http://lists.xensource.com/xen-devel
>>>>     
>>>
>>>   
> 
>