hw/virtio/virtio-pci: Remove VirtIOPCIProxy::ignore_backend_features field

The VirtIOPCIProxy::ignore_backend_features boolean was only set
in the hw_compat_2_7[] array, via the 'x-ignore-backend-features=on'
property. We removed all machines using that array, lets remove
that property, simplify by only using the default version.

Reviewed-by: Mark Cave-Ayland <mark.caveayland@nutanix.com>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
Link: https://lore.kernel.org/r/20260108033051.777361-27-zhao1.liu@intel.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

hw/virtio/virtio-pci.c

@@ -2040,8 +2040,7 @@ static void virtio_pci_device_plugged(DeviceState *d, Error **errp)
      * Virtio capabilities present without
      * VIRTIO_F_VERSION_1 confuses guests
      */
-    if (!proxy->ignore_backend_features &&
-            !virtio_has_feature(vdev->host_features, VIRTIO_F_VERSION_1)) {
+    if (!virtio_has_feature(vdev->host_features, VIRTIO_F_VERSION_1)) {
         virtio_pci_disable_modern(proxy);
 
         if (!legacy) {
@@ -2443,8 +2442,6 @@ static const Property virtio_pci_properties[] = {
                     VIRTIO_PCI_FLAG_MODERN_PIO_NOTIFY_BIT, false),
     DEFINE_PROP_BIT("page-per-vq", VirtIOPCIProxy, flags,
                     VIRTIO_PCI_FLAG_PAGE_PER_VQ_BIT, false),
-    DEFINE_PROP_BOOL("x-ignore-backend-features", VirtIOPCIProxy,
-                     ignore_backend_features, false),
     DEFINE_PROP_BIT("ats", VirtIOPCIProxy, flags,
                     VIRTIO_PCI_FLAG_ATS_BIT, false),
     DEFINE_PROP_BIT("x-ats-page-aligned", VirtIOPCIProxy, flags,

include/hw/virtio/virtio-pci.h

@@ -150,7 +150,6 @@ struct VirtIOPCIProxy {
     uint16_t last_pcie_cap_offset;
     uint32_t flags;
     bool disable_modern;
-    bool ignore_backend_features;
     OnOffAuto disable_legacy;
     /* Transitional device id */
     uint16_t trans_devid;