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From 9f13c7165566f442484fa6c335950465ed6a2050 Mon Sep 17 00:00:00 2001
From: Cornelia Huck <>
Date: Wed, 17 Apr 2019 13:57:38 +0100
Subject: [PATCH 21/24] s390x/pci: Warn when adding PCI devices without the
 'zpci' feature

RH-Author: Cornelia Huck <>
Message-id: <>
Patchwork-id: 85803
O-Subject: [RHEL-8.1.0 qemu-kvm PATCH v2 21/24] s390x/pci: Warn when adding PCI devices without the 'zpci' feature
Bugzilla: 1699070
RH-Acked-by: David Hildenbrand <>
RH-Acked-by: Thomas Huth <>
RH-Acked-by: Jens Freimann <>

From: David Hildenbrand <>

We decided to always create the PCI host bridge, even if 'zpci' is not
enabled (due to migration compatibility). This however right now allows
to add zPCI/PCI devices to a VM although the guest will never actually see
them, confusing people that are using a simple CPU model that has no
'zpci' enabled - "Why isn't this working" (David Hildenbrand)

Let's check for 'zpci' and at least print a warning that this will not
work as expected. We could also bail out, however that might break
existing QEMU commandlines.

Reviewed-by: Thomas Huth <>
Signed-off-by: David Hildenbrand <>
Message-Id: <>
Reviewed-by: Collin Walling <>
Signed-off-by: Cornelia Huck <>
(cherry picked from commit 703fef6fcf3edcbf169c90b6196fcf88f9e9765a)
Signed-off-by: Cornelia Huck <>
Signed-off-by: Danilo C. L. de Paula <>
 hw/s390x/s390-pci-bus.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/hw/s390x/s390-pci-bus.c b/hw/s390x/s390-pci-bus.c
index a0f7245..1ba7873 100644
--- a/hw/s390x/s390-pci-bus.c
+++ b/hw/s390x/s390-pci-bus.c
@@ -864,6 +864,12 @@ static void s390_pcihost_pre_plug(HotplugHandler *hotplug_dev, DeviceState *dev,
     S390pciState *s = S390_PCI_HOST_BRIDGE(hotplug_dev);
+    if (!s390_has_feat(S390_FEAT_ZPCI)) {
+        warn_report("Plugging a PCI/zPCI device without the 'zpci' CPU "
+                    "feature enabled; the guest will not be able to see/use "
+                    "this device");
+    }
     if (object_dynamic_cast(OBJECT(dev), TYPE_PCI_DEVICE)) {
         PCIDevice *pdev = PCI_DEVICE(dev);