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Date: Fri, 18 Aug 2017 13:32:14 +0200
From: Cornelia Huck <cohuck@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH] s390x/tcg: specification exception for
 unknown diag
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To: Thomas Huth <thuth@redhat.com>
Cc: qemu-devel@nongnu.org, rth@twiddle.net, agraf@suse.de, borntraeger@de.ibm.com

On Fri, 18 Aug 2017 13:26:15 +0200
Thomas Huth <thuth@redhat.com> wrote:

> On 18.08.2017 13:00, Cornelia Huck wrote:
> > While the PoP is silent on the issue, z/VM documentation states
> > that unknown diagnose codes trigger a specification exception.
> > We already do that when running with kvm, so change tcg to do so
> > as well.  
> 
> I just tried on a z/VM guest what happens if I call diag with an
> unsupported code, and the Linux kernel then crashes with a specification
> exception, indeed. So this sounds like the right thing to do!

For reference, here's the relevant hunk in z/VM documentation:
https://www.ibm.com/support/knowledgecenter/SSB27U_6.4.0/com.ibm.zvm.v640.hcpb4/hcpb432.htm

> 
> > This is on top of "s390x: wire up diag288 in tcg".  
> 
> May I suggest to order the patches the other way round? ... that's less
> code churn that way.

Let me detangle my branches...