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Date: Wed, 11 Oct 2017 14:20:53 +0200
From: Cornelia Huck <cohuck@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v1 4/5] s390x/pci: Refuse to realize
 VFIO-PCI if AIS needed but supported
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To: Pierre Morel <pmorel@linux.vnet.ibm.com>
Cc: Alex Williamson <alex.williamson@redhat.com>, qemu-devel@nongnu.org, borntraeger@de.ibm.com, pasic@linux.vnet.ibm.com, zyimin@linux.vnet.ibm.com, agraf@suse.de

On Tue, 10 Oct 2017 18:01:53 +0200
Pierre Morel <pmorel@linux.vnet.ibm.com> wrote:

> Since in the case we have no AIS in KVM only PCI is impacted, do you 
> think we can fence IRQFD for MSI with
> 
> kvm_msi_via_irqfd_allowed = false;
> 
> in kvm_arch_init_irq_routing() ?

Hm, it seems we never set that for s390x... does that imply that we
never support irqfd for pci anyway?

> 
> In fact, if we also verify the AIS availability in the same routine we 
> can avoid the ugly include of vfio/pci.h

If we can get the serialization right (and setting that value to false
does indeed have the desired effect), that's probably the way to go.