From 6657d0c1018ab44ae680376463ac3f0421548fb4 Mon Sep 17 00:00:00 2001
From: Laszlo Ersek <lersek@redhat.com>
Date: Thu, 23 Dec 2021 11:36:59 +0100
Subject: [PATCH] launch-libvirt: place our virtio-net-pci device in slot 0x1e

The <qemu:commandline> trick we use for adding our virtio-net-pci device
in the libvirt backend can conflict with libvirtd's and QEMU's PCI address
assignment. Try to mitigate that by placing our device in slot 0x1e on the
root bus. In practice this could only conflict with a "dmi-to-pci-bridge"
device model, which libvirtd itself places in slot 0x1e. However, given
the XMLs we generate, and modern QEMU versions, libvirtd has no reason to
auto-add "dmi-to-pci-bridge". Refer to
<https://libvirt.org/formatdomain.html#controllers>.

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2034160
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Message-Id: <20211223103701.12702-2-lersek@redhat.com>
Reviewed-by: Richard W.M. Jones <rjones@redhat.com>
Tested-by: Richard W.M. Jones <rjones@redhat.com>
(cherry picked from commit 5ce5ef6a97a58c5e906083ad4e944545712b3f3f)
---
 lib/guestfs-internal.h | 11 +++++++++++
 lib/launch-libvirt.c   |  4 +++-
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/lib/guestfs-internal.h b/lib/guestfs-internal.h
index 4799ee0a1..0b46f0070 100644
--- a/lib/guestfs-internal.h
+++ b/lib/guestfs-internal.h
@@ -147,6 +147,17 @@
 #define VIRTIO_DEVICE_NAME(type) type "-pci"
 #endif
 
+/* Place the virtio-net controller in slot 0x1e on the root bus, on normal
+ * hardware with PCI. Refer to RHBZ#2034160.
+ */
+#ifdef HAVE_LIBVIRT_BACKEND
+#if defined(__arm__) || defined(__s390x__)
+#define VIRTIO_NET_PCI_ADDR ""
+#else
+#define VIRTIO_NET_PCI_ADDR ",addr=1e.0"
+#endif
+#endif
+
 /* Guestfs handle and associated structures. */
 
 /* State. */
diff --git a/lib/launch-libvirt.c b/lib/launch-libvirt.c
index 026dc6b26..5842319df 100644
--- a/lib/launch-libvirt.c
+++ b/lib/launch-libvirt.c
@@ -1834,7 +1834,9 @@ construct_libvirt_xml_qemu_cmdline (guestfs_h *g,
       } end_element ();
 
       start_element ("qemu:arg") {
-        attribute ("value", VIRTIO_DEVICE_NAME ("virtio-net") ",netdev=usernet");
+        attribute ("value", (VIRTIO_DEVICE_NAME ("virtio-net")
+                             ",netdev=usernet"
+                             VIRTIO_NET_PCI_ADDR));
       } end_element ();
     }
 
-- 
2.31.1