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,

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@xxxxxxxxxx> 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@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:spz6vmdothb2n
> > > > jf
> > > > 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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