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

[Allan Graves <allan.graves@xxxxxxxxxx>]

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@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
> >
> >
> >
> >
> >
> > _______________________________________________
> > Xen-devel mailing list
> > Xen-devel@xxxxxxxxxxxxxxxxxxx
> > http://lists.xensource.com/xen-devel
> >     
>
>   
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