AW: VHD BUG in xen4.0 when install windows2008

["Heiko Wundram" <modelnine@modelnine.org>]

As I'm seeing a similar behavior of tapdisk2 (see my recent posts to xen-users, especially "blktap2, also broken in current pv_ops stable-2.6.32.x?"), I can confirm that at least in my testing (I've done some more over the weekend, re. that message), this is indeed an "SMP-related" problem, but only for HVM-64bit domains.

What I can basically say is that:

1) Uni/Multi/32-bit/64-bit PV domains run properly.
1) Uni-VCPU, 32-bit HVM domains run properly.
2) Multi-VCPU, 32-bit HVM domains run properly.
3) Uni-VCPU, 64-bit HVM domains run properly.
4) Multi-VCPU, 64-bit HVM domains cause tapdisk2 to segfault, sometimes, under heavy I/O, and if that happens, causes the Dom0-kernel to freeze/lock up, Bug, and/or all other kinds of undefined behavior, where I really haven't made out a pattern yet.

Interestingly, these errors do not happen when using the "normal" blkback-driver, and I'm very positive (at least that's what happened during my testing) that it's specific to Multi-VCPU, 64-bit HVM domains that the crash occurs, independent of the number of VCPUs bound to Dom0.

--- Heiko.


-----Ursprüngliche Nachricht-----
Von: xen-devel-bounces@lists.xensource.com [mailto:xen-devel-bounces@lists.xensource.com] Im Auftrag von Daniel Stodden
Gesendet: Sonntag, 9. Mai 2010 20:41
An: Pasi Kärkkäinen
Cc: Ian Pratt; yingbin wang; xen-devel@lists.xensource.com
Betreff: Re: [Xen-devel] VHD BUG in xen4.0 when install windows2008

On Sat, 2010-05-08 at 15:52 -0400, Pasi Kärkkäinen wrote:
> On Sun, May 09, 2010 at 01:02:42AM +0800, yingbin wang wrote:
> >    I have try xenlinux 2.6.18.8. the problem also appear. os can not startup.
> > 
> >    Windows 2008 R2 Standard Edition 64(disk size: 20G, C:\ 15G, D:\ 5G) on
> >    vhd file, the problem appear.
> >    does anyone successfully install Windows 2008 R2 Standard Edition 64(disk
> >    size: 20G, C:\ 15G, D:\ 5G) on vhd file??
> >    env : (xen4.0, kernel2.6.31.13) or (xen4.0, kernel2.6.18.8)
> > 
> 
> Looking at the log (below) it seems the 'tapdisk2' process segfaults (crashes).
> Sounds like a bug in it..

This is the loop pulling requests from the userspace I/O ring.
Missing a sanity check on the message content, hence the crash.

I would have bet it's smp-related, but sounds as if not.

Daniel


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