From aa757665c90914e69db3f16b11753c6d936b9bf0 Mon Sep 17 00:00:00 2001
From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Date: Thu, 17 Aug 2017 09:45:36 +0200
Subject: [PATCH 3/4] Workaround rhel6 ctrl_guest_offloads machine type
 mismatch

RH-Author: Dr. David Alan Gilbert <dgilbert@redhat.com>
Message-id: <20170817094536.12740-3-dgilbert@redhat.com>
Patchwork-id: 76022
O-Subject: [RHEL-7.5/7.4.z/7.3.z/7.2.z qemu-kvm PATCH v2 2/2] Workaround rhel6 ctrl_guest_offloads machine type mismatch
Bugzilla: 1480428
RH-Acked-by: Eduardo Habkost <ehabkost@redhat.com>
RH-Acked-by: Michael S. Tsirkin <mst@redhat.com>
RH-Acked-by: Thomas Huth <thuth@redhat.com>

From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

RHEL6's 6.5 and 6.6 machine types enable the ctrl_guest_offloads
feature on virtio-net-pci, unfortunately RHEL7's definition of the
6.5 and 6.6 machine types are missing that flag.

This works around it by allowing an incoming migration with the
guest flag set (for the bad machine types).

Fixing the machine type definitions would break migration from this
version to an earlier 7.x.

Note: Restarting the VM after this import will still keep the old
(broken) machine type and turn the feature off.

(cherry picked from commit 73fe1f6ffd03f49f4be4b0482fdd2611aa9a17ca)

          Heavy conflicts from backport, mostly around structure
          of properties

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
 hw/i386/pc_piix.c          |  9 +++++++++
 hw/virtio/virtio.c         | 26 +++++++++++++++++++++++++-
 include/hw/virtio/virtio.h |  1 +
 3 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c
index f4cf2b5..b043124 100644
--- a/hw/i386/pc_piix.c
+++ b/hw/i386/pc_piix.c
@@ -908,8 +908,13 @@ static QEMUMachine pc_machine_rhel700 = {
         .driver   = "virtio-net-pci",\
         .property = "any_layout",\
         .value    = "off",\
+    },{\
+        .driver = "virtio-net-device",\
+        .property = "__com.redhat_rhel6_ctrl_guest_workaround", \
+        .value = "on",\
     }
 
+
 static void pc_compat_rhel660(QEMUMachineInitArgs *args)
 {
     pc_compat_rhel700(args);
@@ -1031,6 +1036,10 @@ static QEMUMachine pc_machine_rhel650 = {
         .driver   = "virtio-net-pci",\
         .property = "ctrl_mac_addr",\
         .value    = "off",\
+    },{\
+        .driver   = "virtio-net-device",\
+        .property = "__com.redhat_rhel6_ctrl_guest_workaround", \
+        .value    = "off",\
     }
 
 static void pc_compat_rhel640(QEMUMachineInitArgs *args)
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index fe6b032..e3af5ae 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -18,6 +18,7 @@
 #include "hw/virtio/virtio.h"
 #include "qemu/atomic.h"
 #include "hw/virtio/virtio-bus.h"
+#include "include/hw/virtio/virtio-net.h"
 
 /* The alignment to use between consumer and producer parts of vring.
  * x86 pagesize again. */
@@ -888,8 +889,24 @@ int virtio_set_features(VirtIODevice *vdev, uint32_t val)
     VirtioBusClass *vbusk = VIRTIO_BUS_GET_CLASS(qbus);
     VirtioDeviceClass *k = VIRTIO_DEVICE_GET_CLASS(vdev);
     uint32_t supported_features = vbusk->get_features(qbus->parent);
-    bool bad = (val & ~supported_features) != 0;
+    bool bad;
+    uint64_t ctrl_guest_mask = 1ull << VIRTIO_NET_F_CTRL_GUEST_OFFLOADS;
+
+    if (vdev->rhel6_ctrl_guest_workaround && (val & ctrl_guest_mask) &&
+          !(supported_features & ctrl_guest_mask)) {
+        /*
+         * This works around a mistake in the definition of the rhel6.[56].0
+         * machinetypes, ctrl-guest-offload was not set in qemu-kvm for
+         * those machine types, but is set on the rhel6 qemu-kvm-rhev build.
+         * If an incoming rhel6 guest uses it then we need to allow it.
+         * Note: There's a small race where a guest read the flag but didn't
+         * declare it's useage yet.
+         */
+        fprintf(stderr, "RHEL6 ctrl_guest_offload workaround\n");
+        supported_features |= ctrl_guest_mask;
+    }
 
+    bad = (val & ~supported_features) != 0;
     val &= supported_features;
     if (k->set_features) {
         k->set_features(vdev, val);
@@ -1223,6 +1240,12 @@ static int virtio_device_exit(DeviceState *qdev)
     return 0;
 }
 
+static Property virtio_properties[] = {
+    DEFINE_PROP_BOOL("__com.redhat_rhel6_ctrl_guest_workaround", VirtIODevice,
+                     rhel6_ctrl_guest_workaround, false),
+    DEFINE_PROP_END_OF_LIST(),
+};
+
 static void virtio_device_class_init(ObjectClass *klass, void *data)
 {
     /* Set the default value here. */
@@ -1230,6 +1253,7 @@ static void virtio_device_class_init(ObjectClass *klass, void *data)
     dc->init = virtio_device_init;
     dc->exit = virtio_device_exit;
     dc->bus_type = TYPE_VIRTIO_BUS;
+    dc->props = virtio_properties;
 }
 
 static const TypeInfo virtio_device_info = {
diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
index d9bfe4c..0c4e963 100644
--- a/include/hw/virtio/virtio.h
+++ b/include/hw/virtio/virtio.h
@@ -121,6 +121,7 @@ struct VirtIODevice
     bool vm_running;
     VMChangeStateEntry *vmstate;
     char *bus_name;
+    bool rhel6_ctrl_guest_workaround;
 };
 
 typedef struct VirtioDeviceClass {
-- 
1.8.3.1