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Date: Fri, 7 Jul 2017 15:04:52 +0200
From: Cornelia Huck <cohuck@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH RFC 5/7] s390x/pci: fence off instructions
 for non-pci
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To: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: qemu-devel@nongnu.org, agraf@suse.de, thuth@redhat.com, pmorel@linux.vnet.ibm.com, zyimin@linux.vnet.ibm.com

On Fri, 7 Jul 2017 14:55:23 +0200
Christian Borntraeger <borntraeger@de.ibm.com> wrote:

> On 07/07/2017 02:21 PM, Cornelia Huck wrote:
> > If a guest running on a non-pci build issues a pci instruction,
> > throw them an exception.
> > 
> > Signed-off-by: Cornelia Huck <cohuck@redhat.com>
> > ---
> >  target/s390x/kvm.c | 24 ++++++++++++++++++++++++
> >  1 file changed, 24 insertions(+)
> > 
> > diff --git a/target/s390x/kvm.c b/target/s390x/kvm.c
> > index a3d00196f4..c5c7c27a21 100644
> > --- a/target/s390x/kvm.c
> > +++ b/target/s390x/kvm.c
> > @@ -1160,6 +1160,9 @@ static int kvm_clp_service_call(S390CPU *cpu, struct kvm_run *run)
> >  {
> >      uint8_t r2 = (run->s390_sieic.ipb & 0x000f0000) >> 16;
> > 
> > +#ifndef CONFIG_PCI
> > +    return -1;
> > +#endif  
> 
> Instead of this ifdefing, can you use the cpu model to decide if the instruction
> should be available? We need to do this anyway for proper handling.
> 
> You can then fence off the PCI bits in the CPU model for
> CONFIG_PCI == off.

Sounds like a good idea, I'll give it a try.

We'll probably also want to fence off the sclp facility bit via that
mechanism.