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

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

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@xxxxxxxxxx> 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:spz6vmdothb2njf
> b+state:results 
> 
> 
> 
> Anyone have a solution to this? :)
> 
> Allan
> 
> 
> 
> 
> 
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> Xen-devel@xxxxxxxxxxxxxxxxxxx
> http://lists.xensource.com/xen-devel



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