Re: [Xen-devel] XEN 4.1.3-rc1 bug, spinlock acquired twice

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Mon, 30 Jan 2012, Paulian Bogdan Marinca wrote:
> On 30 January 2012 11:32, Stefano Stabellini
> <stefano.stabellini@xxxxxxxxxxxxx> wrote:
> > On Sat, 28 Jan 2012, Keir Fraser wrote:
> >> On 27/01/2012 23:20, "Paulian Bogdan Marinca" <paulian@xxxxxxxxxxx> wrote:
> >>
> >> > I have a testing intel machine with 4 physical cpus running 64 bit Xen
> >> > 4.1.3-rc1.
> >> >
> >> > I have a particular linux VM for which at its kernel boot time ( as
> >> > domU ) it makes the XEN and Dom0 unresponsive (even the XEN serial
> >> > console freezes indefinitely). The domU linux kernel is 3.2.1 and has
> [...]
> >
> > That's right, this scenario should not be possible because whenever
> > XENFEAT_hvm_pirqs is available, XENFEAT_hvm_callback_vector should also
> > be available.
> > In any case I'll submit a patch to Linux to make sure this doesn't
> > happen, explicitly checking for xen_have_vector_callback.
> > What is your Linux kernel version? Could you please post your kernel
> > config as well?
> 
> Yes, you are right, this does not happen normally in a booting kernel.
> What happens is that I needed to test my own PV drivers in all
> possible scenarios,
>  so I hacked the domU linux kernel to "believe" that XEN does not have
> XENFEAT_hvm_callback_vector, basically I forced a
> 
> xen_have_vector_callback = 0;
> 
> in enlighten.c in domU kernel. This is probably why it triggered this
> unusual situation.
> 
> I attach my kernel config (btw is actually a 3.0.6 kernel not 3.2.1)
> 
> I will try to apply your patch against XEN.

In that case it is a matter of protecting Xen against misbehaving
guests, so I would rather have the patch below than try to handle the
case correctly.



> > diff --git a/xen/arch/x86/physdev.c b/xen/arch/x86/physdev.c
> > index df92cc7..7d89ed6 100644
> > --- a/xen/arch/x86/physdev.c
> > +++ b/xen/arch/x86/physdev.c
> > @@ -93,6 +93,11 @@ int physdev_map_pirq(domid_t domid, int type, int 
> > *index, int *pirq_p,
> >
> > Â  Â  if ( domid == DOMID_SELF && is_hvm_domain(d) )
> > Â  Â  {
> > + Â  Â  Â  Â if ( !is_hvm_pv_evtchn_domain(d) )
> > + Â  Â  Â  Â {
> > + Â  Â  Â  Â  Â  Â ret = -EINVAL;
> > + Â  Â  Â  Â  Â  Â goto free_domain;
> > + Â  Â  Â  Â }
> > Â  Â  Â  Â  ret = physdev_hvm_map_pirq(d, type, index, pirq_p);
> > Â  Â  Â  Â  goto free_domain;
> > Â  Â  }
>

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